Carbon tubulars better than clinchers for dealing with brake track heat on descents?

[cyan]

Heard on a ride today that carbon tubulars are less susceptible to brake track heat problems than clinchers because the the track section are thicker and structurally stronger. Not sure if there is any truth/science about that.

Could any tubular owners share their experiences?

[ultraman6970]

I dont use carbon tubulars, but aluminum just because of costs. That being said, it makes sense what they told you, you go figure if its true or if somebody did a test to confirm it. With aluminum you dont have to worry pretty much of anything, clinchers or tubulars.

[FriarQuade]

If we are talking carbon wheels, tubulars are absolutely more reliable and safer in heavy braking conditions. But it doesn't have anything to do with the brake track.

In a clincher the rim is part of the pressurized structure. So as you brake and the heat increases tire pressure the rim takes part of those forces. As the resins in the carbon laminate reach their plastic state the pressure from the tire pushes out on the brake track, creating a failure.

In a tubular the entire pressure vessel is contained with in the tire, meaning it will hold full pressure even if it's not on a rim. So when a tubular heats up under heavy breaking the rim doesn't see any extra forces and as a result is significantly more reliable.

[StephenCL]

Well said above...I can tell you that a good buddy of mine, who is a very good descender and likes to go very fast, has gone through 4, yes 4 sets of Enve Clincher Carbons... they finally just told him he needs to move to tubulars!

They have all delammed at the brake track, and he only brakes before the corner and does not ride his brakes at all...

Stephen

[false_Aest]

What the holy man said.
I would never, ever ride on rim brake CF clinchers in the mountains. I've seen too many folks ruin their rims descending around here -- these are good, high quality, respectable MFGs not just open mold stuff.


In my own experience I have yet to have an issue with a tubular CF rim and I've definitely done some stupid shiz with them.

[pianobike]

I've had some early gen clincher rims delaminate in the CA 95deg heat with fast descents- no fun, but they held air! Tubulars are the safest choice.
Check out Tim Smith's GS Astuto (in Tokyo), he's studied rim shapes/resins/weave and has a great handle on rims that resist delamination.

[FlashUNC]

If you want carbon wheels, tubular is the only way to go imo.

[oldpotatoe]

if you want new wheels, tubular is the only way to go imo.

fify...:)

[Blown Reek]

If we are talking carbon wheels, tubulars are absolutely more reliable and safer in heavy braking conditions. But it doesn't have anything to do with the brake track.

In a clincher the rim is part of the pressurized structure. So as you brake and the heat increases tire pressure the rim takes part of those forces. As the resins in the carbon laminate reach their plastic state the pressure from the tire pushes out on the brake track, creating a failure.

This has everything to do with the brake track.

[dem]

This has everything to do with the brake track.

Certainly more mass, and higher temperature resins, and a better insulating brake track will help. But all resins will fail at high temperature, and the description above is accurate regarding the forces that make carbon clincher failure a problem.

I only ride carbon clinchers with disc brakes (500K ascent/year)

[Wayne77]

Well said above...I can tell you that a good buddy of mine, who is a very good descender and likes to go very fast, has gone through 4, yes 4 sets of Enve Clincher Carbons... they finally just told him he needs to move to tubulars!

They have all delammed at the brake track, and he only brakes before the corner and does not ride his brakes at all...

Stephen

I know exactly who you’re talking about. I’ve been on carbon tubulars for 3 years now (thanks to you!) and with all the long steep mtn descents around here I’m not going back to carbon clinchers. I got to the bottom of the Powder mtn descent, which is the steepest climb in Utah by a wide margin and my tubular brake tracks were sizzling hot...I use the correct methods for high speed descending too. I’m not a paranoid person by nature, and in fact I have a fairly high risk tolerance with downhill riding but I really don’t think I’d ever want do that descent on cf clinchers. The worst case scenario / brake track failure possibility makes me shudder to think about.

The other side of the sword is if there IS a clincher fail of some sort also causing rapid loss of tire pressure on a fast descending corner, the rim is going to be right on the pavement and things will go south very quickly. There are extreme occasions even with tubulars of course, but with a tubular the tire is going to stay put to maintain traction for a controlled stop.

Another related question comes to mind...is the cf clincher overheating brake track risk being discussed here better or worse with a tubeless setup? Or maybe it makes no difference. Maybe Im wrong but doesn’t a tubeless tire exert more pressure on the rim? I keep hearing people tell me that I can inflate a gravel tire on a tubeless rim to higher pressures with a tube.

[Wayne77]

Certainly more mass, and higher temperature resins, and a better insulating brake track will help. But all resins will fail at high temperature, and the description above is accurate regarding the forces that make carbon clincher failure a problem.

I only ride carbon clinchers with disc brakes (500K ascent/year)

Another key point. I suppose I should clarify by including “rim brake” in my statements about not ever wanting to do long/fast descending on cf clinchers

[martl]

Heard on a ride today that carbon tubulars are less susceptible to brake track heat problems than clinchers because the the track section are thicker and structurally stronger. Not sure if there is any truth/science about that.

Could any tubular owners share their experiences?

Carbon fibre is incredibly strong in direction of the fiber (tensional stress) but sucks at dealing with bendings, as this stresses mostly the resin instead of the fiber.
A clincher does suffer bending force on the brake sides from tire pressure and from the brakes.
So, making a good a CFK clincher is either a challenge (if you're an optimist) or a bad idea (if you're a pessimist). When i was still actively scanning the market which was like 5 years ago, there were very few manufacturers i would have trusted to get it right.

About brake heating, CFK in general does a bad job of getting the heat away as opposed to alloy, and tubulars deal better with heat than clinchers because there can be no direct contact between the tube and the rim. On the other hand, the tubular glue may react to the heat as well; this is a konwn phenomenon even when using alloy tubulars.

When descending alone, i never had any issues with either CFK tubulars or alloy clinchers. I have been in a field of 500 riders being lead downhill by a leading car at an average speed of 35km/h which forced everyone to descend with brakes applied from top to botton and the soundtrack was comparable to a large group of lemmings in a minefield - tires explodedliterally all the time. Can't tell if there was a majority of one rim type affected :)

[quickfeet]

Just buy a fancy new disc brake wonder bike and you’ll never need to worry about rim brake tracks again.

But for real, some rims are better than others when it comes to rim brake tracks on clinchers. Do your research and you’ll be fine.

[pdmtong]

What is the sustained temperature and duration the brake track of a given CF clincher rim would need to heat to in order for it to fail? And how does that translate into rider weight pad pressure descent slope and speed? How is that affected by drag : pulse brake techniques?

Folks living where there are multi mile high speed downhills. - does anyone there use CF clinchers? Isn't enve in Utah? What do they say?

I think if you want a universal rule then it would be carbon for tubulars for a rim brake application.

Yet enve and campagnolo to name a few offer CF clinchers - are these without fine print?

[happycampyer]

This is a longstanding and well-known issue. Not sure if the video is still on their website, but a few years ago when Zipp redesigned their clincher rims to withstand greater braking heat, they made a video showing the heat effects of braking on carbon rims. My recollection is that, when they were doing R&D for the new rims, they tested pretty much every name-brand wheel available and all failed their test except one (I have heard indirectly from a source that I believe to be reliable that the wheel that passed was the Hyperon clincher, which makes sense since Hyperons are ridiculously strong rims).

Personally, the only carbon clincher wheels I would ride would be for disc brakes. All of my carbon wheels for rim brakes are tubulars.

[pdonk]

Raoul Luescher http://luescherteknik.com.au/ provides lots of insight on this topic both on his web site and with "carbon maven" on you tube.

https://www.youtube.com/watch?v=ET1jRVynOBA

[earlfoss]

I have both carbon tubulars (Zipp 303), and clinchers (Bontrager D3 Aeolus 5). They've both done what they're supposed to with no problems. I've taken the Bontragers down the gnarliest descents in the L.A. area, given them some heavy braking, and they're totally fine. I suppose it's possible that prolonged braking on looooonnnnngggggggg descents might be another story, but for 99.9% of the situations I've have them in, they'll do the job just fine.

[Mark McM]

What is the sustained temperature and duration the brake track of a given CF clincher rim would need to heat to in order for it to fail? And how does that translate into rider weight pad pressure descent slope and speed? How is that affected by drag : pulse brake techniques?


The Alto Cycling carbon clincher rim brake heat test:

https://bikerumor.com/2017/12/08/alto-cycling-spark-melts-carbon-clinchers-w-multi-brand-rim-brake-test/


I believe this test was discussed on the forum last year.

[hobbanero]

the issue with a softening brake track leading to blowouts on carbon clinchers is well trodden....though at 180 pounds I have never had an issue on name brand carbon clinchers made in the last 5 years on any of the steep descents in the Bay Area.

I have seen someone with carbon tubies heat the rim enough to soften the glue and the tire rolled. That could have been a bad glue job.

Coming off Mt Diablo in the Haute Route event really confirmed for me though that disc brakes are awesome. My rim brakes were doing the job, but by the bottom were making a lot of noise and pulsing. I have been down the same 3500' descent on discs and they were consistently good all the way down.

Seems like if you live in a steep area you should skip past clincher v tubie and go straight to tubeless clincher discs.

[fogrider]

I've had good luck with Reynolds Blue pads...and they now have the "power" pads that they claim to be 33% better in the dry, and I'll say they are about that much better! They claim to keep the rims cooler...

[verticaldoug]

ZIPP claims they worked with a supplier for a newer heat resistant resin for their clincher rims. I have the 303s and with the new brake pads, I think these are great.

Although you can still get the old cork brakes if you want that nostalgic smell of burnt cork first thing in the morning ride.

[glepore]

No question its documented. The temperature at which you're at risk depends on the "transition temperature" of the epoxy used, which varies from manufacturer to manufacturer. Another factor is braking style-short sharp braking followed by cooling is much less likely than constant medium braking without "off" periods.

As mentioned earlier, tubulars don't have the force against the bead, so its not a problem in most instances. And you're less likely to melt the glue on a carbon rim for the same reason they deform at the brake track-carbon doesn't conduct heat well, thus less heat gets transmitted to the rim bed.

[Dave]

I've logged over 35,000 miles in the Colorado mountains and never had a problem with aluminum clincher rims. If I had rim issues, I'd switch to aluminum or disc brakes.

[Mark McM]

I've had good luck with Reynolds Blue pads...and they now have the "power" pads that they claim to be 33% better in the dry, and I'll say they are about that much better! They claim to keep the rims cooler...

How do they support the claim that these brake pads keep the rim cooler? Brakes convert kinetic energy (energy of motion) into heat. For the same amount of braking, the same amount of heat is generated. How much the heat raises the temperature will depend on the ability to dissipate the heat (i.e. conduct and convect the energy away). The brake pads won't change the ability of the rim to conduct/convect energy, so the only way that the pads can keep the rims cooler is if the pads themselves conduct/convect heat better. But brake pads are so small (compared to the rim), I just don't see how the pads can make a big difference in the rate of heat dissipation.

[false_Aest]

How do they support the claim that these brake pads keep the rim cooler? Brakes convert kinetic energy (energy of motion) into heat. For the same amount of braking, the same amount of heat is generated. How much the heat raises the temperature will depend on the ability to dissipate the heat (i.e. conduct and convect the energy away). The brake pads won't change the ability of the rim to conduct/convect energy, so the only way that the pads can keep the rims cooler is if the pads themselves conduct/convect heat better. But brake pads are so small (compared to the rim), I just don't see how the pads can make a big difference in the rate of heat dissipation.

You and I have wondered the same thing.

The only thing that I could come up with is that they're grabbier so you can brake later and release earlier thereby allowing the rim more time to cool down before the next brake engagement.

[fogrider]

I'm not a scientist...but Reynolds requires use if their pads or it voids the warranty. And use in the SF bay area has been pretty good with the exception of one of my brakes. I got the new 'power' pads and the do work better and pretty much as advertised. How do they support the claim that these brake pads keep the rim cooler? Brakes convert kinetic energy (energy of motion) into heat. For the same amount of braking, the same amount of heat is generated. How much the heat raises the temperature will depend on the ability to dissipate the heat (i.e. conduct and convect the energy away). The brake pads won't change the ability of the rim to conduct/convect energy, so the only way that the pads can keep the rims cooler is if the pads themselves conduct/convect heat better. But brake pads are so small (compared to the rim), I just don't see how the pads can make a big difference in the rate of heat dissipation.

Sent from my Moto G (5) Plus using Tapatalk

[verticaldoug]

How do they support the claim that these brake pads keep the rim cooler? Brakes convert kinetic energy (energy of motion) into heat. For the same amount of braking, the same amount of heat is generated. How much the heat raises the temperature will depend on the ability to dissipate the heat (i.e. conduct and convect the energy away). The brake pads won't change the ability of the rim to conduct/convect energy, so the only way that the pads can keep the rims cooler is if the pads themselves conduct/convect heat better. But brake pads are so small (compared to the rim), I just don't see how the pads can make a big difference in the rate of heat dissipation.

I think the braking track on the newer carbon rims looks slightly bigger. The newer brake pads by all the wheel companies have a larger surface area. They claim the new diagonal grooves on the pads channel air over the track and brakes to help cools while moving. I think the science of polymers and resins has really progressed in recent years. If you think the advances Boeing has made with carbon fiber in its airplanes and how suppliers like Toray had to respond, it makes sense the technology will trickle down to other uses.
All these little changes probably add up but the manufacturer claims are still probably exaggerated.

[Mark McM]

I think the braking track on the newer carbon rims looks slightly bigger. The newer brake pads by all the wheel companies have a larger surface area. They claim the new diagonal grooves on the pads channel air over the track and brakes to help cools while moving. I think the science of polymers and resins has really progressed in recent years. If you think the advances Boeing has made with carbon fiber in its airplanes and how suppliers like Toray had to respond, it makes sense the technology will trickle down to other uses.
All these little changes probably add up but the manufacturer claims are still probably exaggerated.

I have no doubt that changes in the materials and construction of the rim brake track can aide in the dissipation of brake heat, and therefore limit temperature - but the claim was about brake pads reducing rim temperature.

I don't buy the claim about grooves in the pads keeping the rims cool. The pads only cover a small area of the rim, while the rest of the rim surface is open to the air, and the grooves are only a small part of the pad area. A tiny bit of extra air on the rims isn't going to make a significant difference (That being said, a little extra pad ventilation can improve pad/rim contact when operating at high temperatures, but the question isn't about brake force, it's about heat dissipation). I think the idea that the pads reduce rim temperature can be chalked up as another questionable marketing claim.