Recommendation against carbon clinchers

[weaponsgrade]

I just registered for the Levi granfondo ride. One of the release waivers was for you to acknowledge their recommendation against carbon clinchers b/c of overheating. Kinda interesting. I've read anecdotal reports of overheating but this is the first time I've read of it from a major voice.

[akelman]

Two years ago, I was riding about 150 yards behind someone whose wheel, a carbon clincher I'm guessing, blew up on one of the steep descents on King Ridge Road. No, I mean it literally blew up. As in, KAPOW! And down he went. He was lucky and wasn't too badly hurt, but man it was a scary scene.

Generally speaking, the organizers of Levi's seem to be pretty good about encouraging people to leave their blingy, high-zoot gear at home. They make sure riders understand that the terrain is rugged, that help isn't necessarily going to be close by, and that it might make sense to emphasize reliability rather than drool-worthiness. But then the riders typically ignore the warnings and show up on thirteen-pound carbon bikes with 1200-gram carbon clinchers. Fortunately, most of them are just fine anyway.

[akelman]

I should note that the first year I did the event I rode an IF Planet X with Campy Protons on it. Last year, I rode my Ottrott with Neutrons. I was lucky I wasn't riding a cross bike, as the weather was horrible, and the dual-pivot brakes made a huge difference on some of the steeper downhills. Plus, the Ottrott is the only bike I own that makes me feel at all comfortable descending anything scarier than my driveway.

[pdmtong]

I UNDERSTAND THAT CARBON CLINCHER WHEELS ARE HIGHLY DISCOURAGED
Carbon clincher wheels are strongly discouraged because they can fail/explode under the extreme braking necessary on sections of this route.

Each year we have riders experience failure of carbon clincher-type wheels. The extreme braking necessary on some of the descents along this route heat up the rim beyond their failure point and they explode. Don't be one of those people.

Ever go on a ride in which there are hay bales set up on some of the corners?
My ottrott/kysriums is perfect for this ride

[merckx]

There are so many great lightweight alloy wheels available now like Fulcrum Zeros and Shamals at 1440g's, why risk the chance with carbon clinchers? I did a very hilly circuit a few years ago to get in a 10,000 foot climbing day. Some of the descents were at 18% and very technical with T intersections at the base so you had to be on the brakes. I was using a pair of carbon tubs, and by the end of the day, they were cooked. I didn't have any blow-outs, but the wheels were unusable after the ride. I moved on to alloy wheels after that experience.

[mvrider]

Hmmm, I wonder if my Moots P-X with disc brakes would be the ticket. :cool:

[Charles M]

I understand that some models are very simply not performing under a lot of stress...

That said, Zipp have had virtually no issues with their newest Carb Clinchers.

And I dont mean "virtually" in an advert sense. I mean despite LARGE volume, they've had less than 5 rims come back in and of those, braking heat and side wall deformation wasn't the issue...

Their tech for these wheels is head and shoulders better than the typical Carb Clincher.

That route is tough and I'm not saying "ignore the warning". But I wouldnt mind hearing from a few folks running firecrest clinchers...

[sg8357]

I take it that Volagi and Veloflex are major Grand Fondue sponsors ?

[Chance]

Curious about what type of failures carbon clinchers are experiencing.

If braking heat is the issue, why is it not affecting carbon tubulars too? Is it the added heat increasing tire pressure to the point of blowing out the rims’ braking surfaces? If so, are they that much more fragile compared to alloy rims or is it that carbon rims get hotter under same braking?

[David Kirk]

Curious about what type of failures carbon clinchers are experiencing.

If braking heat is the issue, why is it not affecting carbon tubulars too? Is it the added heat increasing tire pressure to the point of blowing out the rims’ braking surfaces? If so, are they that much more fragile compared to alloy rims or is it that carbon rims get hotter under same braking?

The heat issue isn't really any worse with clinchers as compared to tubulars but the way the heat ends up affecting the rim is different. With a tubular the rim gets hot and this makes the tire hot and the pressure rises. Not a huge deal as long as you didn't start with 170 psi in the tires.

With clinchers the rims gets hot and this makes the tire pressure go up and this tries to spread the sidewalls of the rims - the part the tire is hooked into. There can be two types of failure. Either the tire pressure goes up and literally blows the tire out and off of the rim - or - even worse - the very hot sidewalls of the rim fail where the tire hooks in and the sidewall blows off the rim taking the tire with it.

If you look at the sidewall of a clincher rim it's a thin flat section that a ridge that holds the tire from coming off. The failures are typically right at the thin part of the sidewall at the base of the ridge.

It's doesn't happen often but it happens - and when it does it makes a big mess.

Dave

[redir]

I think I would just heed the warning, why not? You really don't want to be THAT guy. :beer:

[Chance]

So they both get hot but aluminum clinchers can take the temperature better than carbon clinchers without weakening as much.

Sounds like a bad application for carbon. Maybe they should save carbon clinchers for discs. :rolleyes:

[benitosan1972]

It's a ride, not a race. So you'd think the weekend warriors could listen to function > form. But still, some won't. They want to look like a TDF-pro at all costs...

[Kontact]

A major carbon rim player had a whole huge run of early rims (tubular and clincher) where the epoxy used didn't have a high enough working temperature for long braking. This series of failures and very quiet non-recall could have contributed to a bad rep for carbon rims in general.

Any braking that can heat a clincher up to failure, is also likely to do some damage to tubular glue. Plan accordingly.


And discs are prone to brake fade in long, dry descents. I don't really think they are a solution to mountain road riding, but they are nice when it's wet.

[jimcav]

they should demo a bunch of their clinchers there since they claim to not have the heat issues of other carbon clinchers
madfiber if you are reading, send me a pair and i'll do that fondo!
jim

[rockdude]

This is a big problem here in CO. Bottom-line Carbon Clincher provide little/or no performance benefit at higher price and have durability issues. If you want the benefit of carbon wheels, go tubular.

[benitosan1972]

Or, if you are super-pro, just don't touch the brakes while descending those loooong moooountain deeeescents... you'll be the first to the bottom though I'm not sure you'll be in one piece, haha! Kkkkaaaaammmmiiiikkkkaaaazzzzeeeeeeee!!!!!!!!! :banana:

[christian]

Carbon clinchers are like Fiero-based Lamborghini kit cars. Except they'd cost as much as (or more than) a Lamborghini.

[bikerboy337]

+1 to this...

i had two sets of carbon clinchers for about a year... had a few too many scary experiences with braking... especially with T intersections after long descents in the rain... sold and switched to aluminum...


There are so many great lightweight alloy wheels available now like Fulcrum Zeros and Shamals at 1440g's, why risk the chance with carbon clinchers? I did a very hilly circuit a few years ago to get in a 10,000 foot climbing day. Some of the descents were at 18% and very technical with T intersections at the base so you had to be on the brakes. I was using a pair of carbon tubs, and by the end of the day, they were cooked. I didn't have any blow-outs, but the wheels were unusable after the ride. I moved on to alloy wheels after that experience.

[benb]

And discs are prone to brake fade in long, dry descents. I don't really think they are a solution to mountain road riding, but they are nice when it's wet.

Let's not forget the elephant in the room.. no matter what wheels, tires, or brakes you use there are smart ways to brake and stupid ways to brake.

Seems like the discs you are talking about are pretty ridiculously horrible but for any type of brake the rider shouldn't be dragging the brake.. let the bike run when it's straight, brake hard before the corner, let the bike run through the corner onto the next straight.. doing that should minimize the chance of a problem regardless of equipment..

Real curious about fade with discs.. I have descended quite a few mountain roads that were ~13% with sections up to 20% and no matter how careful I am with aluminum clinchers + rim brakes I always have some degree of fade. It's always in the back of my head that poor technique with that equipment could be fatal. At least once in the rain I ended up walking the descent because it just wasn't safe once the rims were wet. Seems like I'd be pretty unhappy going down those roads on carbon clinchers.

But with my mountain bike with discs those same roads are a walk in the park.. even just the rear brake makes it so easy a child could descend the same road safely and I can safely descend the road much much faster. So I'm wondering Kontact, what kind of gimpy discs were you using?

edit: Just looked at the profile for the Levi Gran Fondo and they're claiming it doesn't get steeper then 10%.. just how bad are these rims/brakes? :rolleyes:

[Chance]

But with my mountain bike with discs those same roads are a walk in the park.. even just the rear brake makes it so easy a child could descend the same road safely and I can safely descend the road much much faster. So I'm wondering Kontact, what kind of gimpy discs were you using?


This issue comes up with tandem drag brakes too. Have no personal experience in that area but many teams seem to overcome problems. Drum brakes got hot and faded some too in extreme conditions and were used for decades.

[FlashUNC]

So I shouldn't bring my full carbon front and rear disc wheels for this ride then?

[torquer]

The heat issue isn't really any worse with clinchers as compared to tubulars but the way the heat ends up affecting the rim is different. With a tubular the rim gets hot and this makes the tire hot and the pressure rises. Not a huge deal as long as you didn't start with 170 psi in the tires.
...Dave
Sorta thread drift, but since Dave raised the issue...
Isn't softening of the glue the greater issue with tubulars as they heat up?
Sure, an added 10 psi due to rim heat transfer is fine, but wasn't Beloki's well-documented crash in front of a certain Texan during a Tour stage descent the result of his tire coming unstuck from a carbon rim? I'll bet that wasn't a one-off example, either, just a You-Tube favorite.

[old_fat_and_slow]

So isn't this why some manufacturers offer carbon clinchers with aluminum braking tracks? Aluminum is a much better conducter of heat than graphite/epoxy. I would imagine that aluminum could dissipate the heat much quicker than carbon fiber.

[firerescuefin]

Dave...just looking at them side by side, the carbon tubular looks to be a better heat sink by design as the heat is dissipated laterally and vertically away from the tire, while the carbon clincher wall/braking surface is the primary heat sink...which by surface area alone is not very efficient at absorbing/dissapating.

Apologies in advance to the engineers out there if the terminology is wrong.





The heat issue isn't really any worse with clinchers as compared to tubulars but the way the heat ends up affecting the rim is different. With a tubular the rim gets hot and this makes the tire hot and the pressure rises. Not a huge deal as long as you didn't start with 170 psi in the tires.

With clinchers the rims gets hot and this makes the tire pressure go up and this tries to spread the sidewalls of the rims - the part the tire is hooked into. There can be two types of failure. Either the tire pressure goes up and literally blows the tire out and off of the rim - or - even worse - the very hot sidewalls of the rim fail where the tire hooks in and the sidewall blows off the rim taking the tire with it.

If you look at the sidewall of a clincher rim it's a thin flat section that a ridge that holds the tire from coming off. The failures are typically right at the thin part of the sidewall at the base of the ridge.

It's doesn't happen often but it happens - and when it does it makes a big mess.

Dave

[David Kirk]

Sorta thread drift, but since Dave raised the issue...
Isn't softening of the glue the greater issue with tubulars as they heat up?
Sure, an added 10 psi due to rim heat transfer is fine, but wasn't Beloki's well-documented crash in front of a certain Texan during a Tour stage descent the result of his tire coming unstuck from a carbon rim? I'll bet that wasn't a one-off example, either, just a You-Tube favorite.

I agree completely.

On another note of brake fade. I've never experienced brake fade with disc brakes - either hydro or cable pulled. I did have issue with the very early disc brakes 'packing up' (fluid expands and without a reservoir it makes the brake lever throw shorter so the brakes effectively come on sooner) but this is really the opposite of fade. They still had lots of power. I have trouble picturing disc brake fade unless one were to boil the fluid and that seems very unlikely. I can't get my cable pulled road discs to fade regardless of how stoopidly I drag them down fast descents.

dave

[tannhauser]

And discs are prone to brake fade in long, dry descents. I don't really think they are a solution to mountain road riding, but they are nice when it's wet.

To each their own, but I much, much prefer discs over calipers for our long, dry descents.

Best braking is ultimate stopping power with tons of modulation, something carbon wheels lack.

[torquer]

So isn't this why some manufacturers offer carbon clinchers with aluminum braking tracks? Aluminum is a much better conducter of heat than graphite/epoxy. I would imagine that aluminum could dissipate the heat much quicker than carbon fiber.
Just about all the early "carbon" clinchers (certainly Zipp, anyway) used an Al brake track for this reason.

Another factor I've read is carbon's poor performance in resisting bending, which is what happens to the cantilevered sidewalls of clincher rims; I'm not sure if this is made worse as the temperature (due to braking) rises.

Others (Mavic, Bontrager) provide a non- or minimally structural carbon fairing inside an AL rim. These tend to be aero, but heavy.

Shimano's strutural composite of a u-shaped extruded aluminum upper and v-shaped carbon lower profile looks to me like the best of both worlds; not super aero, granted, and not celestially light, but still making optimal use of both materials' inherent advantages.

[Bob Ross]

Their tech for these wheels is head and shoulders better than the typical Carb Clincher.

I didn't realize there was such a thing. How many companies make carbon clinchers, four? five?


edit: Nevermind, read the rest of the thread. I am no longer interested in carbon clinchers!

[cdimattio]

[QUOTE=Chance]So they both get hot but aluminum clinchers can take the temperature better than carbon clinchers without weakening as much. /QUOTE]


I would term it that Aluminum conducts thermal energy and is much more effective at dissipating heat in an application like this.

[tannhauser]

Someone mentioned Volagi...

Theoretically it's the perfect GF bike with discs and a bit of frame suspension built in.

Of course it is - born of extensive r&d on bombed out norcal routes.

It's the right tool for the job.

[redir]

Sorta thread drift, but since Dave raised the issue...
Isn't softening of the glue the greater issue with tubulars as they heat up?
Sure, an added 10 psi due to rim heat transfer is fine, but wasn't Beloki's well-documented crash in front of a certain Texan during a Tour stage descent the result of his tire coming unstuck from a carbon rim? I'll bet that wasn't a one-off example, either, just a You-Tube favorite.
In Beloki's case he was going down anyway. A lot of guys who roll tubes are in situations that no tire is going to save. I've never done huge descents quite like that but I need a screwdriver to get tubes off of my rims. That comes from years of gluing on cyclocross tubes. But even so with a slide and chatter at 90 degrees forward motion like the Beloki crash it doesn't matter.

[Jawn P]

On another note of brake fade. I've never experienced brake fade with disc brakes - either hydro or cable pulled.

I have had brake fade once and it was by far the most terrifying experience of my life.

In the Wilderness 101 endurance mountain bike race there is a descent down a trail called Sassafras that is by far the steepest thing I've ever ridden. I had my chest on the seat and was on both my brakes as hard as I could and was still going probably like 20 mph down this long descent.

So I think only under the most extreme conditions are newer hydro setups prone to fade.

[jpw]

So they both get hot but aluminum clinchers can take the temperature better than carbon clinchers without weakening as much.

Sounds like a bad application for carbon. Maybe they should save carbon clinchers for discs. :rolleyes:

+1 Bingo!

[jpw]

Hmmm, I wonder if my Moots P-X with disc brakes would be the ticket. :cool:

Good choice if the geo and rider are as one descending.

[rice rocket]

I have had brake fade once and it was by far the most terrifying experience of my life.

In the Wilderness 101 endurance mountain bike race there is a descent down a trail called Sassafras that is by far the steepest thing I've ever ridden. I had my chest on the seat and was on both my brakes as hard as I could and was still going probably like 20 mph down this long descent.

So I think only under the most extreme conditions are newer hydro setups prone to fade.

Or you showed up w/ the wrong pads. ;)

[Chance]

I would term it that Aluminum conducts thermal energy and is much more effective at dissipating heat in an application like this.
Actually, we can't really know how important heat transfer within the rim is without knowing a lot more information. It's probably right but not necessarily right. We could go into scenarios of each to show why that's the case but this is not the right place to do so.

It mostly depends on whether heat transfer within the rim cross section is adequate enough so that most of the rim is near a uniform temperature. Beyond that it depends on how well the rim transfers heat to the surrounding air to reach a steady-state high-temperature during long duration braking.

Carbon like that used for bike frames at one time was suspected of not resisting high temperatures very well. There were warnings against leaving carbon frames locked in closed cars parked in sun because it could ruin a frame. They've probably improved by now, but at the higher temperatures of a rim under severe braking maybe it can be an issue if not designed properly. OTOH race cars now use carbon in brake systems.

[jpw]

Sorta thread drift, but since Dave raised the issue...
Isn't softening of the glue the greater issue with tubulars as they heat up?
Sure, an added 10 psi due to rim heat transfer is fine, but wasn't Beloki's well-documented crash in front of a certain Texan during a Tour stage descent the result of his tire coming unstuck from a carbon rim? I'll bet that wasn't a one-off example, either, just a You-Tube favorite.

Wasn't it the melted road surface that did for Beloki?

[David Kirk]

Wasn't it the melted road surface that did for Beloki?

I think he slid in the road goo and slipped until he hit firm sticky road and that rolled his tire.

dave

[old_fat_and_slow]

Actually, we can't really know how important heat transfer within the rim is without knowing a lot more information. It's probably right but not necessarily right. We could go into scenarios of each to show why that's the case but this is not the right place to do so.

It mostly depends on whether heat transfer within the rim cross section is adequate enough so that most of the rim is near a uniform temperature. Beyond that it depends on how well the rim transfers heat to the surrounding air to reach a steady-state high-temperature during long duration braking.

The source of heat on the braking tracks is friction between brake pads and braking tracks. The aluminum brake tracks are pretty thin, appoximately 1/16 of an inch. The tire and and inner tube on the opposite side of braking track (interior side, the side away from the heat source) are probably not a great heat sink. So just intuitively, I would suspect that the delta-T across an aluminum braking track is minimal. The heat transfer is going to be primarily by conduction, (assuming your brake tracks aren't being subjected to Sahara desert-level direct solar radiation). However, the point I'm getting around to, is that since aluminum is a much better conductor than graphite/epoxy composites, once the brakes are released, the tracks will cool much more quickly (by convection with the air), than the 100% graphite/epoxy wheels. However, if you are descending a long mountain with sustained braking, aluminum is gonna get pretty hot too.

[Charles M]

I didn't realize there was such a thing. How many companies make carbon clinchers, four? five?


edit: Nevermind, read the rest of the thread. I am no longer interested in carbon clinchers!




The point is that Zipp are just not having the same problems with the Firecrest Carbon Clincher that this thread is about...


There were folks at Levi's GF on Zipp CC's in the past. None of the typical carb clincher issues at all.



This thread is going how lots do... Just assume all of X type of thing are the same and run with it. :beer:

[cycle101g]

Every mechanic Ive talked to frowns when the topic comes up. Ive had them multiple times but still will not take them bombing down Mt. Palomar b/c of those same concerns. Although the new Reynolds brake tracks do a great job of dissipating heat.

[jpw]

I think he slid in the road goo and slipped until he hit firm sticky road and that rolled his tire.

dave

French roads :rolleyes:

[David Kirk]

In looking at this thread as a whole I'm afraid that people will get turned off to carbon wheels - clinchers in particular. I don't think they are at all dangerous if used in the right way.

If the rider lives in a flatish place (no long fast descents) then I think they can be great. If on the other hand you live somewhere with long twisty descents (think Boulder CO) then carbon clinchers with rim brakes would not be the best choice.

I live in a mountainous place and for the past 3 years I've been riding Reynolds carbon clinchers and while I think the braking leaves a bit to be desired I in no way found them to be dangerous. I never got the rims hot. But my hills are long and not all that steep so you coast for miles and brush the brakes here and there and that's it. There are on the other hand hills back in NY where I used to ride (West Mountain Rd) that I think could give this set up issues and I doubt I'd use them there. I'd want carbon rims and disc brakes for that stuff.

So don't panic and sell your wheel in fear that your pulling up to a stop sign will result in your death.

Common sense stuff IMO.

dave

[sg8357]

OTOH race cars now use carbon in brake systems.

Disc brake rotors for airplanes and race cars are reinforced carbon-carbon,
a brittle material, not a good rim material.

[akelman]

I don't think they are at all dangerous if used in the right way.

Hearing Pez's frustration with the direction of the thread, I should note that my initial point was very much the one made above: the organizers of Levi's want participants to use the right tools for the job. In my case, I often ride carbon clinchers and have never had a problem with them. But they're probably not the greatest choice for when I'm going to ride very steep, very long descents on very bad roads, which is precisely the case on King Ridge during Levi's Gran Fondo. And that's because for someone like me, a rider who doesn't have a ton of experience riding those kinds of roads, it's a good place to be extra cautious. If I add the wrong wheels into an already volatile mix, I might be asking for problems.

As for the new Zipps, I've heard nothing but good things about them. But then again, I've never had any carbon brake tracks -- on Edge, Zipp, or Reynolds -- heat up on me. That's probably because I'm going too slow to create any real friction when I brake.

[old_fat_and_slow]

In looking at this thread as a whole I'm afraid that people will get turned off to carbon wheels - clinchers in particular. I don't think they are at all dangerous if used in the right way.

If the rider lives in a flatish place (no long fast descents) then I think they can be great. dave
I concur. I use aluminum brake-track Zipps as my everyday wheels (see Ti Eddy link in sig, below). Been doing so for at least two years now. But again, I don't have any really long descents in my local area. I'd have to drive a bit to get to the local mountains, where I could ride some "serious descents" and I'm too lazy.

[wtex]

In Beloki's case he was going down anyway. A lot of guys who roll tubes are in situations that no tire is going to save. I've never done huge descents quite like that but I need a screwdriver to get tubes off of my rims. That comes from years of gluing on cyclocross tubes. But even so with a slide and chatter at 90 degrees forward motion like the Beloki crash it doesn't matter.

Was he on carbon? That was 2003, correct? I've been watching the Telekom documentary on Netflix and I haven't seen any carbon so far.

[Ti Designs]

I have a theory about carbon wheels - if you're fast enough to need them your team should buy them for you. If you're not fast enough to need them, they're really not going to help.

There, problem solved!

[jpw]

Was he on carbon? That was 2003, correct? I've been watching the Telekom documentary on Netflix and I haven't seen any carbon so far.

Yes, 2003;

http://www.youtube.com/watch?v=RtZhG2kWVLY

Poor Beloki.

[old_fat_and_slow]

I have a theory about carbon wheels - if you're fast enough to need them your team should buy them for you. If you're not fast enough to need them, they're really not going to help.

There, problem solved!

Aw C'mon . But they make me look fast when I pull into Starbucks. Are you telling me that just because I have a huge pot gut, the carbon wheelset doesn't offset that, and make me look fast anyway ??? Damnnit ! ! That just really effes up my whole plan. ;)

[Sasha18]

Yes, carbon clinchers are dangerous. The most interesting nugget in this thread was buried right here.


I can't get MY cable pulled road discs to fade
dave
Dave, what bike do you have with road discs?

[Ti Designs]

Aw C'mon . But they make me look fast when pull into Starbucks.


So does a full zebra kit, but you don't see grand fondos banning Dave, do you?

[rice rocket]

Are the zebra stripes vertical or horizontal?

[Ti Designs]

Are the zebra stripes vertical or horizontal?

Yes.

[skijoring]

Yes, carbon clinchers are dangerous. The most interesting nugget in this thread was buried right here.


Dave, what bike do you have with road discs?


I'm hoping for something cool to cruise across my flickrstream
during NAHBS...Discs are coming, if not from Mr. Kirk then surely others.

[David Kirk]

Yes, carbon clinchers are dangerous. The most interesting nugget in this thread was buried right here.


Dave, what bike do you have with road discs?

Yep - I am riding a prototype JKS X set up with discs. I just got in from a ride on them about 15 minutes ago - crazy to be able to road ride in Montana during January but I've been out riding and testing different set-ups all of this never ending fall we are having.

dave

[David Kirk]

I'm hoping for something cool to cruise across my flickrstream
during NAHBS...Discs are coming, if not from Mr. Kirk then surely others.

I'll be showing a fillet brazed cross bike with discs in the raw at the show. I still need to build it but that's the plan.

dave

[skijoring]

I'll be showing a fillet brazed cross bike with discs in the raw at the show. I still need to build it but that's the plan.

dave

58 top tube? :beer: :)

With rack and fender braze-ons? :) :beer:

[David Kirk]

58 top tube? :beer: :)

With rack and fender braze-ons? :) :beer:

Nope - 60 cm top tube and stripped bare cross race bike. Just my size in fact! Hmmmm?

dave

[Kirk007]

Yep - I am riding a prototype JKS X set up with discs. I just got in from a ride on them about 15 minutes ago - crazy to be able to road ride in Montana during January but I've been out riding and testing different set-ups all of this never ending fall we are having.

dave

We're sending you a present from Seattle, unless it heads south. Endless fall ended here this week!

Look forward to hearing more about this setup though!

[lhuerta]

This thread is going how lots do... Just assume all of X type of thing are the same and run with it. :beer:

+1


First, just like lawyer tabs on a fork, now the organizers of a mass ride (actually their lawyers) are claiming that you need to leave your carbon clinchers at home. It is not the technology that is flawed, rather the user of the technology. Keep in mind that many of the so-called blowouts we hear about can often be attributed to user error, either a poorly installed tube that gets pinched between tire and rim OR someone riding their brakes down an entire descent.


Second, remember that carbon rim technology is changing very quickly. In 2011, top manufacturers like Reynolds, Easton and Enve all added significant weight to their carbon clinchers (in some cases close to 100 grams compared to their previous model), as a result of the added carbon and new resins that were used in their brake tracks. All three of these manufactures had previous documented failures due to heat build up and their re-design was aimed at addressing these issues. In addition, they all introduced new brake pads with new compounds aimed at reducing heat.

My point is that what we are seeing in carbon clincher technology from 2011 forward is VERY different then the now older tech of pre-2011. So lets not use such broad strokes to characterize all carbon clinchers

I have been riding Reynolds Forty Six carbon clinchers for the last year with great success....even using latex tubes with veloplugs. While there are no long alpine descents in my area there are plenty of short and steep descents that will yield significant brake heat on any rim.

Happy riding,
Lou

[CunegoFan]

Second, remember that carbon rim technology is changing very quickly. In 2011, top manufacturers like Reynolds, Easton and Enve all added significant weight to their carbon clinchers (in some cases close to 100 grams compared to their previous model), as a result of the added carbon and new resins that were used in their brake tracks. All three of these manufactures had previous documented failures due to heat build up and their re-design was aimed at addressing these issues. In addition, they all introduced new brake pads with new compounds aimed at reducing heat.


And yet at the same time tons of people are falling over themselves to buy no name carbon clinchers direct from Asia. How well do those hold up on a long technical descent?

[beeatnik]

http://redkiteprayer.com/?p=6845


"But if you live on the west side of Los Angeles, or anywhere near the Santa Monica Mountains, then you know at least two riders who have melted a set of carbon clinchers. The problem has to do with the crazy, winding nature of the roads that tumble down the canyons to the ocean. They’ve got all the ordered predictability of a schizophrenic’s one-sided conversation. And they are steep as Ferrari prices. That’s not necessarily a bad combination, but what it means is when descending those roads you brake frequently and forcefully. Heat buildup is a given.

I won’t go into whose wheels I’ve destroyed, but I can say I’ve personally seen wheels from Reynolds, Enve, Bontrager and—gasp—Lightweight, all delaminated on descents. Typically, what I see is the brake track melt at one point and air pressure push that portion of the brake track out. I’ve never seen a Zipp wheel fail there, nor have I seen a set of Easton carbon clinchers fail in that way. The issue here is entirely heat buildup."

The above from Patrick Brady who thinks the Las Tunas descent, where a Robert Hyndman was killed, is not a tough descent.

Lou, I'm guessing PB didn't melt his rims due to user error.

[jpw]

Perhaps a good strategy is to ride a new descent with discs first (if you have that type of bike to hand) and see what you're letting yourself in for. Then consider your road bike with alu rims next, and then decide whether life is worth living and try the BEST reputation carbon rims last (which from the consensus of this thread appears to be ZIPP).

[cfox]

I don't understand carbon clinchers. 2012 Zipp Firecrest carbon clincher = 1494 grams. Cfox's "boat anchor" Nemesis tubulars = 1500 grams. Talk to me about aero when your in the front group in Kona. If you want carbon wheels, get tubulars. You will save 300 grams also avoid the attendant braking/sidewall issues. This is not a knock against clinchers (not starting that debate), but it seems that every 'advance' in carbon clincher technology just keeps making them heavier.

[oldpotatoe]

I'm hoping for something cool to cruise across my flickrstream
during NAHBS...Discs are coming, if not from Mr. Kirk then surely others.

They are already 'here'. Mechanical discs on some sort of 'road' bike have been made for as long as Avid mechanical discs have been available. Waterford/Gunnar has made them, Moots has made them..not mysterious at all and perfectly sensible for those that ride in the muck, wet, mud(cross) or tour in the wet, muck, mud or ride a tandem in same.

Wet discs are a whole 'nother animal. Discs have a questionable place on road bikes for for 'enthusiasts', daily riders in the dry, types. BUT not worth the $, complexity, considering any advantage over rim brakes, even with the relatively small percentage of riders who use carbon rim wheels.

Read about a guy that weighed .225 offa a ton, with a 13 pound bike...so yep, there will be wet discs on a road bike that is ridden at average speeds of 15 mph, a hour or 2 a week. And we will bleed the things, install the things, service the things...at $35 per bleed.

[oldpotatoe]

I don't understand carbon clinchers. 2012 Zipp Firecrest carbon clincher = 1494 grams. Cfox's "boat anchor" Nemesis tubulars = 1500 grams. Talk to me about aero when your in the front group in Kona. If you want carbon wheels, get tubulars. You will save 300 grams also avoid the attendant braking/sidewall issues. This is not a knock against clinchers (not starting that debate), but it seems that every 'advance' in carbon clincher technology just keeps making them heavier.

Don't forget the $2500+ also.

[cfox]

Don't forget the $2500+ also.
excellent point

[Grant McLean]

I don't understand carbon clinchers. 2012 Zipp Firecrest carbon clincher = 1494 grams. Cfox's "boat anchor" Nemesis tubulars = 1500 grams. Talk to me about aero when your in the front group in Kona. If you want carbon wheels, get tubulars. You will save 300 grams also avoid the attendant braking/sidewall issues. This is not a knock against clinchers (not starting that debate), but it seems that every 'advance' in carbon clincher technology just keeps making them heavier.

Agreed, on the carbon, but forget the nemesis.
The best all-around wheelset available are the Shimano C24 clinchers.

Spoke count is just as important to 'aero' as rim depth, and having a
16/20 spoke, 1395 gram, durable, serviceable, ti cassette body,
aluminum brake surface wheelset for easily under $1k is a
nemesis killer... just add your favourite 25mm tires.

g

[Kontact]

Let's not forget the elephant in the room.. no matter what wheels, tires, or brakes you use there are smart ways to brake and stupid ways to brake.

Seems like the discs you are talking about are pretty ridiculously horrible but for any type of brake the rider shouldn't be dragging the brake.. let the bike run when it's straight, brake hard before the corner, let the bike run through the corner onto the next straight.. doing that should minimize the chance of a problem regardless of equipment..

Real curious about fade with discs.. I have descended quite a few mountain roads that were ~13% with sections up to 20% and no matter how careful I am with aluminum clinchers + rim brakes I always have some degree of fade. It's always in the back of my head that poor technique with that equipment could be fatal. At least once in the rain I ended up walking the descent because it just wasn't safe once the rims were wet. Seems like I'd be pretty unhappy going down those roads on carbon clinchers.

But with my mountain bike with discs those same roads are a walk in the park.. even just the rear brake makes it so easy a child could descend the same road safely and I can safely descend the road much much faster. So I'm wondering Kontact, what kind of gimpy discs were you using?

edit: Just looked at the profile for the Levi Gran Fondo and they're claiming it doesn't get steeper then 10%.. just how bad are these rims/brakes? :rolleyes:
They weren't mine, they were on a friend's mountain bike. While any brake should have the possibility of fade, small metal on metal discs are going to generate and hold more heat than a 700c rim and a synthetic pad.

So while I know of disc brakes becoming completely unusable from heat, I have yet to hear of a rim brake that faded to zero braking. Have you heard of a rim brake that stopped working from fade?


Anyway, despite the hype I don't think we'll see great riding disc road forks/framesets anytime soon. What we think of as an appropriately compliant fork for good shock absorption and cornering can't support hub-centric braking forces without snapping. Several of my co-workers test rode Volagis, and despite wanting to like them, the front end flexed too much side to side for decent cornering (I assume they did something to the frame to make up for the stiff fork).

Discs are great for bad conditions on big tires. 23 or 25c racing machines are a different matter.

[wai2fast]

Just to add my $0.02 to the conversation: a friend of mine was coming down the Col du Glandon last year during La Marmotte and his carbon clinchers cracked all the way through as he was approaching one of the many downhill turns. I think he said he was JUST starting the descent, so he was still near the top of the mountain and wasn't braking a whole lot just yet. As he sat at the side of the road waiting for support he saw at least a dozen other riders with some sort of malfunction as they approached that corner. Oddly enough all the riders suffering mechanicals were on carbon clinchers as well.

[cfox]

Agreed, on the carbon, but forget the nemesis.
The best all-around wheelset available are the Shimano C24 clinchers.

Spoke count is just as important to 'aero' as rim depth, and having a
16/20 spoke, 1395 gram, durable, serviceable, ti cassette body,
aluminum brake surface wheelset for easily under $1k is a
nemesis killer... just add your favourite 25mm tires.

g
Agree, Shimano wheels are killer, but their aesthetics aren't for everyone. Yes, I'm vain, and the Nemesis look better on my bike (and I prefer tubs). If I had a more modern looking carbon rig, it would have Shimano wheels.

[tannhauser]

And we will bleed the things, install the things, service the things...at $35 per bleed.

Great for the shop.

Hydro's are borderline overkill for even those who "need" discs.

Might as well write you a bigger check while you're replacing my broken alu derailleur hanger because my carbon bike is too stiff.

It goes on...

[tannhauser]

[url]
The above from Patrick Brady who thinks the Las Tunas descent, where a Robert Hyndman was killed, is not a tough descent.

Lou, I'm guessing PB didn't melt his rims due to user error.

Ouch. Patrick is so friggin wrong here.

I think he writes himself into a corner sometimes.

[Grant McLean]

Agree, Shimano wheels are killer, but their aesthetics aren't for everyone. Yes, I'm vain, and the Nemesis look better on my bike (and I prefer tubs).

i totally get that too.

-g

[lhuerta]

Ouch. Patrick is so friggin wrong here.

I think he writes himself into a corner sometimes.

+1

If P. Brady is the guy who writes most of the reviews on RKP then I whole heartedly agree...respectfully, too much hyperbole and not enough substance in his reviews.

For example:
http://redkiteprayer.com/?p=6845...but I can say I’ve personally seen wheels from Reynolds, Enve, Bontrager and—gasp—Lightweight, all delaminated on descents.

...could he be more vague? Which wheels by Reynolds, Enve, etc? And more importantly which model year? Many of us have seen carbon clincher failures or experienced them ourselves, but if I was going to write a review and mention such failures I would want to be SPECIFIC on which wheels have failed (my second point on previous post).

Lou

[Chance]

Second, remember that carbon rim technology is changing very quickly. In 2011, top manufacturers like Reynolds, Easton and Enve all added significant weight to their carbon clinchers (in some cases close to 100 grams compared to their previous model), as a result of the added carbon and new resins that were used in their brake tracks. All three of these manufactures had previous documented failures due to heat build up and their re-design was aimed at addressing these issues. In addition, they all introduced new brake pads with new compounds aimed at reducing heat.

Lou, if not heat where does braking energy go? :confused:

If they mean reducing high temperatures that may be possible. Not sure you can do much about converting almost 100 percent of energy to heat though regardless of materials.

[Bruce K]

I havn't read the whole thread but this has been a worry of mine when I ride Copper Triangle in CO

I have always taken alloy rims

As for where does the energy go if not into heat, some would convert from kinetic to potential energy, wouldn't it?

But yes, most would go into heat. The trick is to either dissipate heat quickly or extend the time it takes to build up. These can be accomplished through structural design or materials or both.

BK

[happycampyer]

I realize that this is a promotional video, but I think it provides an interesting view into the R&D Zipp did w/r/t carbon clincher design:

Firecest Video (http://www.zipp.com/technologies/aerodynamics/firecrest.php)

One question that doesn't appear to be answered (imo) is whether an aluminum rim would dissipate heat better, so that the tire wouldn't fail as early on an alu rim as it would on a carbon rim.

[Bruce K]

They seem to - but part of the issue is braking technique

If you are on a big descent and grab a handful of brake and hang on you get rapid high heat buildup that you can feel if you were to stop and touch the rim. Almost high enough to get mild burn

Modulating your brakes under the same situation allows the rim and pads to cool

The high temp can raise tire pressure and cause tire failure or have the tire blow off the rim. The high temps can also damage carbon.

I used HED J4 clinchers (scandium rim with carbon fairing) at Copper this year and had no issues

BK

[Bob Loblaw]

One concern I have about carbon rims is, notwithstanding the possibility of heat-related explosion, what happens when you have a plain old flat at speed? (http://www.youtube.com/watch?v=Ngv7Iu3y1o0&feature=player_embedded)

BL

[tannhauser]

I realize that this is a promotional video, but I think it provides an interesting view into the R&D Zipp did w/r/t carbon clincher design:

Firecest Video (http://www.zipp.com/technologies/aerodynamics/firecrest.php)

One question that doesn't appear to be answered (imo) is whether an aluminum rim would dissipate heat better, so that the tire wouldn't fail as early on an alu rim as it would on a carbon rim.

What are you talking about. I think the original warning at the start of this thread made that explicit. Of course we can continue to talk about Thermodynamics 101 forever...

Or someone could actually measure heat transfer.

Unless you East Coast guys have mountains with long, hot descents I don't know what applicability this has.

[Kontact]

What are you talking about. I think the original warning at the start of this thread made that explicit. Of course we can continue to talk about Thermodynamics 101 forever...

Or someone could actually measure heat transfer.

Unless you East Coast guys have mountains with long, hot descents I don't know what applicability this has.
A tire failure and a rim failure are pretty different things.

Carbon fiber doesn't dissipate heat better than metal, but it doesn't transfer heat as well as metal, either. So a carbon rim may heat a tire slower than aluminum, even if the rim itself is storing more heat.

I suspect that most "tire failures" from hot carbon rims are actually carbon failures at the rim hook.

[rustychisel]

I suspect that most "tire failures" from hot carbon rims are actually carbon failures at the rim hook.

bingo! My thinking also, was discussing thisn with mates after today's ride and our conclusion - especially for the bigger rider of 80kg + is carbon clinchers are a bad idea. We're talking steep hills (>6% steep and technical descents of more than 3 miles).

[oldpotatoe]

Agreed, on the carbon, but forget the nemesis.
The best all-around wheelset available are the Shimano C24 clinchers.

Spoke count is just as important to 'aero' as rim depth, and having a
16/20 spoke, 1395 gram, durable, serviceable, ti cassette body,
aluminum brake surface wheelset for easily under $1k is a
nemesis killer... just add your favourite 25mm tires.

g

'serviceable'??>?...call around to some decent bike shops and see who has spokes for these.

PLUS under $1000?? How about a DA hubbed wheelset, comparible rims, stainless steel spokes..about the same weight, aero-ness...for $300-$400 less.......

With a spoke just about every bikeshopusa, wil have.

[Chance]

As for where does the energy go if not into heat, some would convert from kinetic to potential energy, wouldn't it?

Don't think simple bike brakes can work that way. To convert kinetic energy to potential energy would mean that there would have to be some form of energy storage for it to be used at a later time. Much like a hybrid car does. It'd be nice if braking kinetic energy could be stored as potential energy for later use to re-accelerate or climb that mountain we just descended, but simple bike braking is just about converting motion energy into heat. And that heat can't be put back to good use.

[Bruce K]

Since we're talking about descents I was thinking that slowing down reduces the kinetic energy of motion and gives you the potential energy to accelerate by releasing the brakes and letting gravity do its thing.

Sort of like a roller coaster. Drag it up a lift hill and you increase the potential energy which turns into kinetic energy when it accelerates down the other side.

Fun stuff to talk about but I also plan to use wheels with alloy rims every time I go somewhere that I know there will be long descents and lots of braking

BK

[Chance]

Carbon fiber doesn't dissipate heat better than metal, but it doesn't transfer heat as well as metal, either. So a carbon rim may heat a tire slower than aluminum, even if the rim itself is storing more heat.
:confused:

There are at least two issues being used almost interchangeably, but probably shouldn’t be. A rims capacity to transfer heat and ability to absorb heat are two completely different things which in large part depend on different material properties. And then there is “dissipate” heat. What does that mean to most people? Is it viewed more like transfer heat or absorb heat? Or a little of both? And for how long? Steady state or transient?

It does seem too technical a subject to discuss by us non-technical guys just interested in riding a bike. The video linked above is revealing though in that it clearly shows that the high temperature zone while braking was limited to the area just adjacent the brake pads. Heat transfer to the remainder of the rim profile seems minimal if we base it on the colors. In that light it would be necessary to compare to aluminum rim since aluminum is such a good conductor of heat. Maybe in an aluminum rim of similar shape heat is transferred to surrounding air from all over the rim thereby reducing maximum temperature near tire.

Good marketing video but not sure it means a lot beyond that they are working on problem and are making some progress.

[Chance]

Fun stuff to talk about but I also plan to use wheels with alloy rims every time I go somewhere that I know there will be long descents and lots of braking

BK
Yeah, don't have much against carbon rims myself but alloy rims work for me because they are cheap, take a beating, can be light enough, last long enough, and can ride fine. Just can't justify the added costs of carbon at this time.

[Kontact]

:confused:

There are at least two issues being used almost interchangeably, but probably shouldn’t be. A rims capacity to transfer heat and ability to absorb heat are two completely different things which in large part depend on different material properties. And then there is “dissipate” heat. What does that mean to most people? Is it viewed more like transfer heat or absorb heat? Or a little of both? And for how long? Steady state or transient?

It does seem too technical a subject to discuss by us non-technical guys just interested in riding a bike. The video linked above is revealing though in that it clearly shows that the high temperature zone while braking was limited to the area just adjacent the brake pads. Heat transfer to the remainder of the rim profile seems minimal if we base it on the colors. In that light it would be necessary to compare to aluminum rim since aluminum is such a good conductor of heat. Maybe in an aluminum rim of similar shape heat is transferred to surrounding air from all over the rim thereby reducing maximum temperature near tire.

Good marketing video but not sure it means a lot beyond that they are working on problem and are making some progress.
Not sure what you are questioning or objecting to. I was illustrating the difference between hot rims and hot tires because one material will attempt to heat everything it touches, and the other will trap it. It doesn't require a doctorate to understand the difference between cooking something in a glass pan vs. aluminum. Tannhauser's post seems to be muddling rims getting hot vs. rims heating the tire, which is why I posted.

[bfd]

Not sure what you are questioning or objecting to. I was illustrating the difference between hot rims and hot tires because one material will attempt to heat everything it touches, and the other will trap it. It doesn't require a doctorate to understand the difference between cooking something in a glass pan vs. aluminum. Tannhauser's post seems to be muddling rims getting hot vs. rims heating the tire, which is why I posted.

My question is with all the problems carbon clinchers appear to have, what's the advantage? Is it weight? stiffer rim?

If its weight, how much lighter are a set of carbon clincher wheels than say these Soul aluminum rim clincher wheels that supposedly weigh in at 1330g for the pair:

http://www.bikesoul.com/2009/index.php?option=com_content&view=article&id=2&Itemid=10

At $500 shipped, these wheels seem like the deal! How would carbon clinchers be an improvement? Good Luck!

[old_fat_and_slow]

Since we're talking about descents I was thinking that slowing down reduces the kinetic energy of motion and gives you the potential energy to accelerate by releasing the brakes and letting gravity do its thing.
...snippage...
BK
No, Chance is correct. Descending from the top of a hill is converting potential energy to kinetic energy. By braking, you are converting some of the kinetic energy to heat. You are correct in stating that braking reduces your kinetic energy (which is a function of velocity). However, you are not converting anything to potential energy. At the top of the hill you have a finite amount of potential energy. If you stop on the descent somewhere. You have consumed some of the potential energy you had at the top. However, you still have some remaining potential energy because you have not descended the entire hill. Braking does not affect potential energy, and you are not adding anything back to your potential energy reserve by braking.

[Bruce K]

I'll buy that.

I'd love to know how much heat (calories, joules, etc) is developed by slowing a 150# rider with a 16# bike from 40mph to 30mph.

My physics isn't that good any more. :rolleyes:

The heat is then lost from this sytem (bike/rider/gravity) to the atmosphere through heat transfer, right? Friction between pad/rim, then conduction from rim to tire, then radiation from rim/tire to atmosphere (not sure there's any convection going on as the sheel system is moving through the air, but again, my physics isn't that good any more....

BK

[old_fat_and_slow]

I'll buy that.
..snippage...
The heat is then lost from this sytem (bike/rider/gravity) to the atmosphere through heat transfer, right? Friction between pad/rim, then conduction from rim to tire, then radiation from rim/tire to atmosphere (not sure there's any convection going on as the sheel system is moving through the air, but again, my physics isn't that good any more....

BK

You were doing great until you got to the heat transfer mechanism between rim/tire to atmosphere, that is by convection, not radiation. Convection is, in general, heat transfer from a solid to a liquid or gas medium.

Yes, I slept in a Holiday Inn Express last night.

[tannhauser]

A tire failure and a rim failure are pretty different things.

Carbon fiber doesn't dissipate heat better than metal, but it doesn't transfer heat as well as metal, either. So a carbon rim may heat a tire slower than aluminum, even if the rim itself is storing more heat.

I suspect that most "tire failures" from hot carbon rims are actually carbon failures at the rim hook.

I've seen tire failures from both materials, doesn't really matter what on the rim fails.

If you guys actually have had a tire failure from heat build up riding in the flats, I'd be impressed.

Say you got an answer to your question - would you then call up Enve and tell them how to manufacture a carbon wheel to your spec?

It's all speculation and "suspecting" without an end or application in the real world. Kind of silly. Fine for a winter's day but let's get real.

[Bruce K]

I know convection is through a gas or liquid but going from the rim to the air is direct contact thus conduction

Once it gets to the air the rise in temperature in the vicinity of the rim would be convection but if the wheel moves forward it removes the heat source that would cause a convection current

I think......

As I said, great coffee table conversation

BK

[Kontact]

I've seen tire failures from both materials, doesn't really matter what on the rim fails.

If you guys actually have had a tire failure from heat build up riding in the flats, I'd be impressed.

Say you got an answer to your question - would you then call up Enve and tell them how to manufacture a carbon wheel to your spec?

It's all speculation and "suspecting" without an end or application in the real world. Kind of silly. Fine for a winter's day but let's get real.
I don't understand your post.

Enve did change the epoxy formulation of their rims because of heat problems.

It isn't flat where I live, and the shop I work for takes customers on tours of the Pyrenees, where heat build up causing rim failures and melting tubular glue has been a factor. So this discussion seems entirely germane to me - I'm the guy who builds those wheels and mounts those tires.

If you are saying that someone who only rides in Florida doesn't need to worry about this stuff, sure, whatever.

[tannhauser]

I don't understand your post.

Enve did change the epoxy formulation of their rims because of heat problems.

It isn't flat where I live, and the shop I work for takes customers on tours of the Pyrenees, where heat build up causing rim failures and melting tubular glue has been a factor. So this discussion seems entirely germane to me - I'm the guy who builds those wheels and mounts those tires.

If you are saying that someone who only rides in Florida doesn't need to worry about this stuff, sure, whatever.


You seem to throw out stuff and talk in circles.

If you don't understand I'm under no obligation to explain it twice.

The point of the thread is this, pay attention: do not use carbon wheels on our event please.

We have mountains here; I consider anything under a 15 minute descent to be flat.

[Bob Ross]

It doesn't require a doctorate to understand the difference between cooking something in a glass pan vs. aluminum.

It does however apparently require something more than a Master's degree in music composition, because until you mentioned that it had never even occurred to me that there might be a difference!

Any yes, I'm a pretty lousy cook.

[Kontact]

The point of the thread is this, pay attention: do not use carbon wheels on our event please.
Oh, if that's all you meant, glad you finally said so. So far you have just referred to other posts, rather than said anything about carbon wheels in the mountains.

The "point" of the thread was to communicate that one particular organization warns against using carbon wheels and asks whether that is sensible or not. You seem to be saying that this warning is implicitly true, and must be followed. Okay, then.

[tannhauser]

Oh, if that's all you meant, glad you finally said so. So far you have just referred to other posts, rather than said anything about carbon wheels in the mountains.

The "point" of the thread was to communicate that one particular organization warns against using carbon wheels and asks whether that is sensible or not. You seem to be saying that this warning is implicitly true, and must be followed. Okay, then.

Didn't think I had to point out the obvious.

If you want to talk about where a rim fails and take that knowledge and apply it to your shop's events, it doesn't really help you formulate a policy other than don't use carbon rims on our event.

From the standpoint of equipping your shop's clients in the Pyrenees I would hope you'd promote using alu rims, just as in Levi's event. It covers your ass better than X brand is ok, Y brand isn't, this model, etc.

[old_fat_and_slow]

I know convection is through a gas or liquid but going from the rim to the air is direct contact thus conduction

Once it gets to the air the rise in temperature in the vicinity of the rim would be convection but if the wheel moves forward it removes the heat source that would cause a convection current

I think......

As I said, great coffee table conversation

BK
Hey, no flip-flopping allowed. First you said ...
...then radiation from rim/tire to atmosphere (not sure there's any convection going on as the sheel system is moving through the air
Now you've changed to ...
...going from the rim to the air is direct contact thus conduction

Flip-flopper :D

I still contend that since the air is being forced past the rim brake tracks by the breeze or by the air as the rider is descending, it is forced convection. But whatever,.....

YMMV

[Kontact]

Didn't think I had to point out the obvious.

If you want to talk about where a rim fails and take that knowledge and apply it to your shop's events, it doesn't really help you formulate a policy other than don't use carbon rims on our event.

From the standpoint of equipping your shop's clients in the Pyrenees I would hope you'd promote using alu rims, just as in Levi's event. It covers your ass better than X brand is ok, Y brand isn't, this model, etc.
It isn't obvious. If it was obvious the OP wouldn't have posted the question or generated over 100 responses.

[tannhauser]

It isn't obvious. If it was obvious the OP wouldn't have posted the question or generated over 100 responses.

If you are a shop mechanic and don't know this and equip bikes for the mountains, this statement is scary.

[firerescuefin]

Tanh...the entire post is regarding clinchers....carbon tubulars, which Kontact is referring is a completely different animal, and completely safe even on long descents...Levis gf does not want carbon clinchers.. No mention of tubulars

[Kontact]

If you are a shop mechanic and don't know this and equip bikes for the mountains, this statement is scary.
Clearly, you didn't read anything I wrote on the subject. I'm not for it, and don't see the point in it.

Whatever my or your opinions are, lot's of people do ride carbon rims in the mountains, and no manufacturer warns against the practice, despite the risk of lawsuits.

[tannhauser]

Tanh...the entire post is regarding clinchers....carbon tubulars, which Kontact is referring is a completely different animal, and completely safe even on long descents...Levis gf does not want carbon clinchers.. No mention of tubulars

Yeah, that part did get muddled, but I have seen carbon tubies have issues with respect to speed modulation.

For a GF or a cyclo-tour, they are endurance events, not races, and a carbon rim or carbon/clincher combo isn't going to get them to the line faster.

[Bruce K]

Can we get away from personal and back to the hardware or the thinking from the OP?

Please?

BK

[tannhauser]

Clearly, you didn't read anything I wrote on the subject. I'm not for it, and don't see the point in it.

Whatever my or your opinions are, lot's of people do ride carbon rims in the mountains, and no manufacturer warns against the practice, despite the risk of lawsuits.

You write a lot of stuff - I can't keep track of everything.

Ok, since you brought it up: why would a manufacturer bring up an issue of their own rims they are trying to sell? That doesn't make any sense.

[tannhauser]

Can we get away from personal and back to the hardware or the thinking from the OP?

Please?

BK

Ok. Just pointing out a mechanic should know the hardware from experience, not the internet.

[PoppaWheelie]

Seems to me the Fondue organizers (or their lawyers) might have had other things in mind when they added the request for folks to leave their carbon clinchers at home. I've seen a pair melt under a 220lb guy on a huge descent, so sure, that's maybe a concern. However it seems to me to be more of an problem that the braking can be not-so-hot and that it gets worse if conditions aren't dry. Given the pitch to Hauser Bridge (as well as to Hwy 1 off the ridge) is super sketch and that it can be wet (fog, etc) at the coast I'm sure they want everyone to have as much stopping power as possible. I did the Fondo route the weekend after the event last year on carbon wheels and never felt that I was in danger of a materials melt-down...but I had the road to myself and it was a bright sunny day. With a few thousand of my closest friends and maybe even some wet I'll be running aluminum wheels for sure at this year's event.

[Chance]

I still contend that since the air is being forced past the rim brake tracks by the breeze or by the air as the rider is descending, it is forced convection. But whatever,.....


Mostly forced convection would be correct. :beer:

However, give Bruce K some credit for mentioning radiation. There is some radiant heat transfer too. It doesn't add up to much, but it's there. ;)

[Kontact]

Can we get away from personal and back to the hardware or the thinking from the OP?

Please?

BK
Great idea. Here's some thoughts on mountain wheels:

Weight, not aerodynamics is the most important performance consideration. Light wheels climb and brake better than heavier ones, and aerodynamics don't help on climbs and aren't needed on descents.

Clinchers and brake heating are always considerations. Brake track wear on aluminum clinchers can also lead to failure when heat causes the tire pressure to rise dramatically. In both cases, starting with relatively low air pressure might be a good idea and using tires with a high blow off pressure, like Contis.

Tubular glue can also be an issue at high temperatures. Which glue bed heats up more; carbon or aluminum? No idea, but I wouldn't be surprised if aluminum transfers more heat to the glue than a carbon rim would. Either way, really gluing the tubular right is a big deal.

I think carbon clinchers are making new strides all the time, and what may have been true of a 2010 model may be totally outdated for a 2012 model. Given the right pad, rim, air pressure and tire combination, a carbon clincher could be just fine for mountain descents, and possibly safer than a tubular.

All carbon rims, tubular or clincher, will structurally fail from heat if the wrong epoxy was used.


I'm not interested in being a guinea pig for carbon rim developers myself, so I'd just use some ultralight alloy rims and good clinchers for mountains. My direct experience is that carbon rim manufacturers do not do everything above the board, and will conceal a known problem with their product. They are also not all knowing, all seeing engineers, and are capable of forgetting about things like brake heat when doing their designs - it is still an infant industry.

[Kontact]

You write a lot of stuff - I can't keep track of everything.

Ok, since you brought it up: why would a manufacturer bring up an issue of their own rims they are trying to sell? That doesn't make any sense.
To prevent people from getting hurt using them incorrectly then suing them. Did you really need to ask?

This is the same reason certain bike frames and components have weight limitations. Does that behavior mystify you as well? How about tire pressure limits and brake wear markings? How will they ever sell that stuff????

[tannhauser]

To prevent people from getting hurt using them incorrectly then suing them. Did you really need to ask?

This is the same reason certain bike frames and components have weight limitations. Does that behavior mystify you as well? How about tire pressure limits and brake wear markings? How will they ever sell that stuff????

Uh, you are definitely talking in circles now.

[Kontact]

Ok. Just pointing out a mechanic should know the hardware from experience, not the internet.
I am speaking from experience. Where do you work?

[Kontact]

Uh, you are definitely talking in circles now.
No, you are. Product limitations and liability are not circular.

[tannhauser]

I am speaking from experience. Where do you work?


Work? Not in a shop.

[tannhauser]

No, you are. Product limitations and liability are not circular.

Ok then...

[shovelhd]

It's a ride, not a race.

[rice rocket]

"Any ride with more than one ego is a race."

- someone wise

[benb]

Kontact.. you need to get some things straight about disc brakes.

It doesn't matter if the disc is smaller then a rim surface.. a drilled disk has plenty of extra surface area to dissipate heat into the air compared to a rim.. and if you look at pad to disc swept area vs pad-to-rim swept area there is probably not much difference.

But besides that.. there is no question metal on metal brakes operate fine at temperatures that will destroy any rubber based rim brake pad in existence, melt any tubular glue, and likely blow out any tire. They won't transfer that heat into the tire or any other place you have to worry about heat causing problems.

[choke]

Whatever my or your opinions are, lot's of people do ride carbon rims in the mountains, and no manufacturer warns against the practice, despite the risk of lawsuits.Coincidentally I happened to be looking at the Boyd Cycling website yesterday and noticed this in regards to their carbon clinchers. If your ride includes very steep descents (long periods of over 10% downhill) where you will have to ride the brakes very hard for a prolonged period of time, carbon clinchers may not be the best idea for that ride.

[Kontact]

Kontact.. you need to get some things straight about disc brakes.

It doesn't matter if the disc is smaller then a rim surface.. a drilled disk has plenty of extra surface area to dissipate heat into the air compared to a rim.. and if you look at pad to disc swept area vs pad-to-rim swept area there is probably not much difference.

But besides that.. there is no question metal on metal brakes operate fine at temperatures that will destroy any rubber based rim brake pad in existence, melt any tubular glue, and likely blow out any tire. They won't transfer that heat into the tire or any other place you have to worry about heat causing problems.
I've witnessed disc brake fade from a long descent - totally zero. I have not witnessed the same with rim brakes.

Have you?

[Chance]

I've witnessed disc brake fade from a long descent. I have not witnessed the same with rim brakes.

Have you?
Can't overheating brake pads glaze them causing brakes to fade?

[Kontact]

Can't overheating brake pads glaze them causing brakes to fade?
They used to. I haven't seen a glazed brake pad come back from the mountains, so maybe it isn't a factor anymore. Soft pads are meant to wear away, not trap the heat.

[Chance]

They used to. I haven't seen a glazed brake pad come back from the mountains, so maybe it isn't a factor anymore. Soft pads are meant to wear away, not trap the heat.
Kontact, what do you mean by “trap heat”?

You’ve used that phrase a couple of times already in this thread and it’s hard to follow what you mean.


FWIW, we shouldn’t make too much of one incident like witnessing one bike with disc brakes that faded. Over the years riders around me at some point have had bars, stems, hubs, rims, seatposts, cranks, axles, and pedals fail. Unless it’s statistically significant we shouldn’t make a big deal of failures. Sh1t occasionally happens with all equipment and we shouldn’t jump to generalized conclusions too quickly. The more a person rides in groups the more likely they will see failures of all kinds.

[Kontact]

Kontact, what do you mean by “trap heat”?

You’ve used that phrase a couple of times already in this thread and it’s hard to follow what you mean.


FWIW, we shouldn’t make too much of one incident like witnessing one bike with disc brakes that faded. Over the years riders around me at some point have had bars, stems, hubs, rims, seatposts, cranks, axles, and pedals fail. Unless it’s statistically significant we shouldn’t make a big deal of failures. Sh1t occasionally happens with all equipment and we shouldn’t jump to generalized conclusions too quickly. The more a person rides in groups the more likely they will see failures of all kinds.
"Trap heat" as in store heat energy from friction. Rim pads are meant to sacrificially wear away rather than build heat like a metal pad does. Older compounds didn't do this very well, so they baked in their own heat and glazed badly.

Metal on metal brake fade is a fact of life on cars, motorcycles, whatever. It only takes a single example to disprove the notion that it can't happen on a bicycle.

The whole point in adopting discs for MTB and cross was that rim brakes work poorly when dirt or water get between the pad and rim. It was never about discs being able to carry a much greater thermal load - a disc is a much smaller piece of metal than a rim, after all. So my sense is that long descents in dry conditions - like what would be the norm for road biking - it would be better to have a brake that doesn't have as great a potential to heat up until it's like teflon. You might halve the life of rim brake pads, but they will work the whole time. And rims never get hot enough to warp, like a steel disc can.

[David Kirk]

I'm testing a road bike with discs now and have been using them for a while. After reading about Kontact's concern about fade I took my bike out yesterday to a long downhill and pedaled as hard as I could down the grade while dragging the front brakes to see if I could get them to overheat and fade. I was able to get the brake to have reduced stopping power by the end of the run but it was by no means gone and would still stop me just fine. I used just the front brake so to get it as hot as possible and of course in real life one would never drag just one brake down a fast hill for a few minutes. This was going about 30 mph for about a mile with the brakes on. I would never come close to this in real life. But still it happened and there was a bit of fade when it got the most hot. This was with organic pads which I was running as they make less noise - but they also have less tolerance for heat and less bite.

A quick switch to metallic pads and a repeat and the results were much different. No fade at all - in fact as they heated up the bite increased and it became harder to hold my speed with the brakes on (legs are feeling it today!).

So I would say that one can have fade with discs but that under normal use the chances of it are very, very small and that it is the likely result of improper set up, use or pad selection. I think if I were going to the Alps and worried about it I'd put in the metallic pads and forget about it. The cool thing being that the pads are exchanged without tools in about 1 minute. I don't think it would be right to put out a blanket statement that 'discs brakes all fade'. Nothing is perfect and everything is a compromise and no one shoe fits all. That said - for riding in the mountains or in the wet/grit/salt...etc I'd pick discs every time. If you don't use a bike this way then discs will probably have little value to you and rim brakes will be more than fine.

Dave

[firerescuefin]

I'm testing a road bike with discs now and have been using them for a while. After reading about Kontact's concern about fade I took my bike out yesterday to a long downhill and pedaled as hard as I could down the grade while dragging the front brakes to see if I could get them to overheat and fade. I was able to get the brake to have reduced stopping power by the end of the run but it was by no means gone and would still stop me just fine. I used just the front brake so to get it as hot as possible and of course in real life one would never drag just one brake down a fast hill for a few minutes. This was going about 30 mph for about a mile with the brakes on. I would never come close to this in real life. But still it happened and there was a bit of fade when it got the most hot. This was with organic pads which I was running as they make less noise - but they also have less tolerance for heat and less bite.

A quick switch to metallic pads and a repeat and the results were much different. No fade at all - in fact as they heated up the bite increased and it became harder to hold my speed with the brakes on (legs are feeling it today!).

So I would say that one can have fade with discs but that under normal use the chances of it are very, very small and that it is the likely result of improper set up, use or pad selection. I think if I were going to the Alps and worried about it I'd put in the metallic pads and forget about it. The cool thing being that the pads are exchanged without tools in about 1 minute. I don't think it would be right to put out a blanket statement that 'discs brakes all fade'. Nothing is perfect and everything is a compromise and no one shoe fits all. That said - for riding in the mountains or in the wet/grit/salt...etc I'd pick discs every time. If you don't use a bike this way then discs will probably have little value to you and rim brakes will be more than fine.

Dave


Dave...Off Topic....and maybe worthy of another thread, can you talk a little bit about the design challenges (weight/strength) of building a road suitable/disc front fork

[zap]

Dave, I may have missed it in one of your earlier posts but what disc brakes are you using.

[David Kirk]

Dave...Off Topic....and maybe worthy of another thread, can you talk a little bit about the design challenges (weight/strength) of building a road suitable/disc front fork

It is a challenge but less so that I thought going into the project. The real issue is distributing the load up the fork blade. The typical disc tab is only about 60 mm long and puts all the load very low on the blade. With some simple design one can spread the load up the blade with no increase in the weight of the tab. The longer tab brings the load up the the part of the blade with the larger diameter where is can easily deal with the load. I made my own tabs for both front and rear with the goal being to spread the load out over as long an area as I practically could and it's worked out well.

Interesting to note is that I worried that the blade with the long tab would be much stiffer than they other blade and that this would cause its own issues - but it's just not the case. I did load and deflection tests on the two blades and found no difference. It made sense when I thought about it and watched the blades flex. Due to the fact that the blades act like a cantilevered beam most of the bending load is take up where the blades meet the crown. The stiffness is a function of cross section and wall thickness and since both blades are the same in this respect at the crown they flex the same under the same load.

One of the other concerns is torsional flex of the braking blade. The brake grabs the rotor and tries to twist the blade. I countered this by making the tabs super-low profile so the caliper is nearly touching the blade - in many cases the caliper is a log way off the blade giving it a longer lever to twist it with. So I am seeing no twist or pull at all. I can brake HARD and the fork flexes back evenly just like it would with a rim brake. No pull to the side, no twist, no shudder - nothing but smooth and powerful braking.

In the rear the challenge is different. Most mount the caliper on the seat stay and then need to triangulate the s-stay to the c-stay to keep things stiff and judder free. I didn't see the sense is mounting the brake to the smallest and thinnest tube on the frame so engineered it to fit on the chainstay. It's a packaging challenge but not exactly rocket surgery. I use large custom c-stays anyway (an whole 'nother topic) and they are more than up to dealing with the braking loads.

I'm also using a smaller rotor in back to help with modulation and prevent lock up so the front and rear have a very balanced feel. It's pretty cool to be going along quickly and grab two big handfuls of brake and have the bike just STOP now. No pulsing, no lock up - just stopping NOW.

Cool stuff.

dave

[David Kirk]

Dave, I may have missed it in one of your earlier posts but what disc brakes are you using.

BB-7's pulled by Sram Red levers.

Dave

[jpw]

BB-7's pulled by Sram Red levers.

Dave

BB7 - I wish there was something like the BB7 with an active inner brake pad. is that not possible with a cable pull disc brake caliper?

[David Kirk]

BB7 - I wish there was something like the BB7 with an active inner brake pad. is that not possible with a cable pull disc brake caliper?

I felt the same way at first and found that once set up properly it wasn't an issue.

I do think that making a cable pull two things on opposite sides of the rotor could be tough to do well. After I figured out the little tricks of setting the BB-7 up I found no noise when free running and great braking. Right at first I was getting some pad rub but that was my fault of not setting them up right.

dave

[tannhauser]

Cool stuff indeed Dave. Thanks for the detailed explanation, particularly about the fork dynamics.

Be careful what you wish for: my Juicy 7s have been problematic for years, as one piston tends to stick, making pad replacement a nightmare. Since it wasn't designed as a "one active pad set up" there is constant rubbing.

Dave, I assume you are mounting the rear brake caliper in between the cs and st?

[zap]

I'm not having much luck getting satisfactory braking from our dual disc BB7 equipped tandem. The brakes work but nothing like the stopping power of our dual pivot/canti equipped tandem on regular rides. Hilly rides-another story what with rim heat build-up.

We also have pad drag for 1-2 miles after hardish braking at the end of descents. Front disc has a slight wobble to it as well so that pulsates.

So, my plan is to get al/steel discs (stiffer) and metallic pads. I might have to take a look at brake cable housing.

[jpw]

I felt the same way at first and found that once set up properly it wasn't an issue.

I do think that making a cable pull two things on opposite sides of the rotor could be tough to do well. After I figured out the little tricks of setting the BB-7 up I found no noise when free running and great braking. Right at first I was getting some pad rub but that was my fault of not setting them up right.

dave

I tend to get uneven pad wear, with more wear outside than inside. Perhaps that's a set up issue.

[David Kirk]

I'm not having much luck getting satisfactory braking from our dual disc BB7 equipped tandem. The brakes work but nothing like the stopping power of our dual pivot/canti equipped tandem on regular rides. Hilly rides-another story what with rim heat build-up.

We also have pad drag for 1-2 miles after hardish braking at the end of descents. Front disc has a slight wobble to it as well so that pulsates.

So, my plan is to get al/steel discs (stiffer) and metallic pads. I might have to take a look at brake cable housing.

Do you have inline cable adjusters in your set up. To get the most power ALL slack needs to be take out of the cable and the lever arm and the only practical way to do this is with an inline adjuster.

I think metallic pads for sure for a tandem.

dave

[jpw]

So, my plan is to get al/steel discs (stiffer) and metallic pads. I might have to take a look at brake cable housing.

What are your discs made of at the moment?

Metallic pads? What are you using now?

[zap]

Discs are Avid steel G3 203 with standard as supplied BB7 Avid pads which I suspect are organic.

Dave, front brake is straight campy brake housing. Rear is jagwire brake housing with cable adjuster as supplied by CoMotion. For both front and rear I preloaded the caliper slightly so there is no cable slack. This effectively replicates what the cable adjuster does.

The tandem was originally equipped with rear disc only-roundagon and that disc was even worse. When we first rode the tandem, hitting the rear brake was comparable to our other tandem with canti rear in the wet.

The other concern I have is that the Campy Record 10 brifter may not have enough brake cable pull compared to Shimano or SRAM.

No one in the tandem world is exactly raving about disc brake performance. Disc brakes are fine for toddling around but you will find that tandem racers prefer dual pivot rim brakes-except for the big hills. Additionally, a critical part, inside adjuster wheel, can melt on long descents. Big problem because if that goes, the pad will fall out.

[David Kirk]

It sounds like the cable pull discs are not up to the task for a tandem. I've talked to others that have had better luck but you are not alone. They just can't handle the extreme heat generated by the weight of the bike and riders and the rear cable is just too long and stretchy to give good power or modulation. Hydro brakes show real promise for this type of application. SRAM will be showing hydro levers soon I'm told.

dave



Discs are Avid steel G3 203 with standard as supplied BB7 Avid pads which I suspect are organic.

Dave, front brake is straight campy brake housing. Rear is jagwire brake housing with cable adjuster as supplied by CoMotion. For both front and rear I preloaded the caliper slightly so there is no cable slack. This effectively replicates what the cable adjuster does.

The tandem was originally equipped with rear disc only-roundagon and that disc was even worse. When we first rode the tandem, hitting the rear brake was comparable to our other tandem with canti rear in the wet.

The other concern I have is that the Campy Record 10 brifter may not have enough brake cable pull compared to Shimano or SRAM.

No one in the tandem world is exactly raving about disc brake performance. Disc brakes are fine for toddling around but you will find that tandem racers prefer dual pivot rim brakes-except for the big hills. Additionally, a critical part, inside adjuster wheel, can melt on long descents. Big problem because if that goes, the pad will fall out.