Just realized the irony of disc brakes on an aero bike.

[zmalwo]

I rarely have these genius moments but this is for sure one of them. The whole purpose of an aero bike is to use them on flat stages where constant speed is high enough that the aero advantage of aero tubes offsets the weight penalty, and the purpose of disc brakes are to avoid overheating of carbon brake tracks on mountain stages where lots of braking take take place. If an aero bike is not used on mountain stage, then caliper brakes would offer better aero gain than disc brake, as well as reducing overall weight close to 6.8kg as aero bikes rarely make to that light. But since everything in the bike industry is about marketing and forced gear retirement, the manufactures probably don't want you to know this. One can argue that discs offer better braking in wet weather, but with recent year pads and brake track improvement I highly doubt discs even offer that much better braking performance.

[zzy]

Your underlying assumptions are incorrect. Even aero bikes have no problem hitting the UCI minimum. Well engineered aero frames with flatmount disc brakes have better aerodynamics than caliper brakes, depending on who you believe.

[KonaSS]

And better braking is better braking, applies to flat roads, wet weather, and downhills.

[Mike V]

"Better"

[weisan]

https://i.ytimg.com/vi/7W7Etl_Vg1A/maxresdefault.jpg

[Burnette]

I rarely have these genius moments but this is for sure one of them. The whole purpose of an aero bike is to use them on flat stages where constant speed is high enough that the aero advantage of aero tubes offsets the weight penalty, and the purpose of disc brakes are to avoid overheating of carbon brake tracks on mountain stages where lots of braking take take place. If an aero bike is not used on mountain stage, then caliper brakes would offer better aero gain than disc brake, as well as reducing overall weight close to 6.8kg as aero bikes rarely make to that light. But since everything in the bike industry is about marketing and forced gear retirement, the manufactures probably don't want you to know this. One can argue that discs offer better braking in wet weather, but with recent year pads and brake track improvement I highly doubt discs even offer that much better braking performance.

You, by yourself, have discovered what nobody in the whole world could. That you can sit on the couch and make stuff up to the point that you believe it true.

[54ny77]

just take a giant bong rip, turn on a hairdryer, and exhale while kneeling in front of bike with hair dryer pointing to rear of bike to see the aerodynamic drag.

then calculate the coefficient of friction as the square root of the thc content multiplied by the v02 max of the rider divided by the gear inches of the top gear configuration.

[Jaybee]

just take a giant bong rip, turn on a hairdryer, and exhale while kneeling in front of bike with hair dryer pointing to rear of bike to see the aerodynamic drag.

then calculate the coefficient of friction is the square root of the thc content multiplied by the v02 max of the rider divided by the gear inches of the top gear configuration.

It's early, but this is a solid POTY candidate:beer:

[XXtwindad]

just take a giant bong rip, turn on a hairdryer, and exhale while kneeling in front of bike with hair dryer pointing to rear of bike to see the aerodynamic drag.

then calculate the coefficient of friction as the square root of the thc content multiplied by the v02 max of the rider divided by the gear inches of the top gear configuration.

Damn this is funny.

[Spdntrxi]

you have a low bar for genius moments

[Joxster]

There was a minor faux pas from Mavic support during the tour last year. Dan Martin recieved a double wheel change at the start of a descent, he's running discs. after 10km of descending the team car comes up and does a bike change. Mainly because things were a bit iffy on the descent and he was running 160 rotors but Mavic gave him 140's

[Burnette]

Your underlying assumptions are incorrect. Even aero bikes have no problem hitting the UCI minimum. Well engineered aero frames with flatmount disc brakes have better aerodynamics than caliper brakes, depending on who you believe.

just take a giant bong rip, turn on a hairdryer, and exhale while kneeling in front of bike with hair dryer pointing to rear of bike to see the aerodynamic drag.

then calculate the coefficient of friction as the square root of the thc content multiplied by the v02 max of the rider divided by the gear inches of the top gear configuration.

Finally, we're doing livingroom research again! I'll bring the Mountain Dew, Doritos and Oreos. Does anybody here have enough hair left that they actually have a hair dryer? If so, bring it.

[54ny77]

landis should lead the research effort.

maybe even come up with cbd chain oil.

Finally, we're doing livingroom research again! I'll bring the Mountain Dew, Doritos and Oreos. Does anybody here have enough hair left that they actually have a hair dryer? If so, bring it.

[oldpotatoe]

There was a minor faux pas from Mavic support during the tour last year. Dan Martin recieved a double wheel change at the start of a descent, he's running discs. after 10km of descending the team car comes up and does a bike change. Mainly because things were a bit iffy on the descent and he was running 160 rotors but Mavic gave him 140's

Hmmmm...I thought the UCI agreed on some sort of ‘standard’ that it would be 12mm TA front and back and 140mm rotors??

BTW, I worked on a tri bike for Drew Scott that had these really awful, integrated into the fork legs and underneath chain stays, blade type brakes that were, VERY aero. Had to be more aero than any caliper/rotor setup...only problem, they didn’t farming work!!!

[R3awak3n]

You, by yourself, have discovered what nobody in the whole world could. That you can sit on the couch and make stuff up to the point that you believe it true.

lol :hello:


I do like that this is not turning out to a disc sucks thread. Well done everyone

[R3awak3n]

landis should lead the research effort.

maybe even come up with cbd chain oil.

dude, CBD chain oil! Seriously, you are into something here (but tbh Floyd probably already coming out with it)

[Bentley]

https://i.ytimg.com/vi/7W7Etl_Vg1A/maxresdefault.jpg

Not understanding this

[Burnette]

Not understanding this

He's giving you visual proof that all modern bikes look better in the small size. And being short of stature myself, I approve of this message.

[bikinchris]

This comment makes me recall the time a guy told me disc wheels can't make sense in cross winds.

[Burnette]

This comment makes me recall the time a guy told me disc wheels can't make sense in cross winds.

Crosswinds are what the domestiques are for.

[zmalwo]

He's giving you visual proof that all modern bikes look better in the small size. And being short of stature myself, I approve of this message.

I think a medium size road bike with a 120mm+ stem and 75cm+ saddle height look the best personally.

[Burnette]

,I think a medium size road bike with a 120mm+ stem and 75cm+ saddle height look the best personally.

Well, I'm way closer to the ground, so from my vantage point medium isn't optimal visualy.

[zmalwo]

,

Well, I'm way closer to the ground, so from my vantage point medium isn't optimal visualy.

Same here, I ride a 52cm I wish I was taller!

[Mzilliox]

I think a medium size road bike with a 120mm+ stem and 75cm+ saddle height look the best personally.

me too, hey, i resemble that

[Bentley]

He's giving you visual proof that all modern bikes look better in the small size. And being short of stature myself, I approve of this message.

What does this have to do with the OP???

[Burnette]

What does this have to do with the OP???

About as much as this post does.

[Burnette]

Same here, I ride a 52cm I wish I was taller!

At my age I have become comfortable in my skin and in cycling it has actually been a bonus. In climbing and in aero in particular, my size has been a benefit.

I live in a hilly area and on big group charity rides, for kicks, on a 25 to 30 mph downhill run I would tuck as tight and low as possible and catch the draft of a group farther up the road, passing a long train very fast on my right.

[bcroslin]

disc hate, couch engineering, bong rips: this thread has everything!

:banana:

[galgal]

At my age I have become comfortable in my skin and in cycling it has actually been a bonus. In climbing and in aero in particular, my size has been a benefit.

I live in a hilly area and on big group charity rides, for kicks, on a 25 to 30 mph downhill run I would tuck as tight and low as possible and catch the draft of a group farther up the road, passing a long train very fast on my right.

Would it not be *relevant* to mention whether you were or were not using disks as you sped past the very long train on your right:)

[Burnette]

disc hate, couch engineering, bong rips: this thread has everything!

:banana:

Weisan is going to check his garage for some wood planks so we can do some sweet jumps. Ask your spouse if you can come over.

[Burnette]

Would it not be *relevant* to mention whether you were or were not using disks as you sped past the very long train on your right:)

No, but I did leave out that my truck and my butt did look awesome.

[rzthomas]

Back on topic, disc brakes on TT bikes make sense because hydro hose can run through all sorts of complicated bends without impairing braking power or feel.

[nickl]

This quote has appeared many times on this and other forums and still rings true for many. Dario had a way to express himself quite succinctly, even with English as his second language.

'One of the main functions of disc brakes is to solve the problems of the carbon wheels manufacturers. Solve problems of the wheels is not my job.' --Dario Pegoretti

[Mikej]

You, by yourself, have discovered what nobody in the whole world could. That you can sit on the couch and make stuff up to the point that you believe it true.

Hey, that’s how I balance my checkbook- so I can buy bike stuff. But lighten up an the op, we’ve all thought of something brilliant st dome point until it was typed out loud-

[Hellgate]

Harsh crowd...geez...

[FlashUNC]

https://media.giphy.com/media/tyttpHaNUYnhi0BR6dq/giphy.gif

[Burnette]

Hey, that’s how I balance my checkbook- so I can buy bike stuff. But lighten up an the op, we’ve all thought of something brilliant st dome point until it was typed out loud-

If you look a few posts up you see that the Op has a sense of humor too and we both see eye to eye because we're both short! :)

[zmalwo]

This quote has appeared many times on this and other forums and still rings true for many. Dario had a way to express himself quite succinctly, even with English as his second language.

'One of the main functions of disc brakes is to solve the problems of the carbon wheels manufacturers. Solve problems of the wheels is not my job.' --Dario Pegoretti

Cannondale: "One of the main functions of threaded BBs is to maintain a problem free BB area. Adding additional weight to have a problem free threaded BB shell but look slightly heavier on my spec sheet is not my job."

[Hawker]

Not understanding this

I think he's suggesting that rider aerodynamics and frontal area mean much more than disc brakes on an aero bike. I'm the guy on the right and I love drafting the guy on the left. :)

[nickl]

Cannondale: "One of the main functions of threaded BBs is to maintain a problem free BB area. Adding additional weight to have a problem free threaded BB shell but look slightly heavier on my spec sheet is not my job."

Apples and oranges comparison. Obviously, Dario made a great deal more sense even though he never claimed to be articulate in English.

'One of the main functions of disc brakes is to solve the problems of the carbon wheels manufacturers. Solve problems of the wheels is not my job.' --Dario Pegoretti

[benb]

Back on topic, disc brakes on TT bikes make sense because hydro hose can run through all sorts of complicated bends without impairing braking power or feel.

Nah.. they make sense because only the most pain loving home mechanic would fix a broken internal hydraulic hose instead of taking it to the approved bike dealer and paying a couple hundred bucks to have it done.

God that sounds bad! (Yes I get that in normal routine maintenance that hydraulic hose will be way less trouble and last way longer than brake cables run internally.)

[echappist]

out of all the new disc-brake equipped aero bikes, only the Cannondale seems to be worth the trouble.

Otherwise, manufacturers are contorting to get people to buy the disc-brake bikes. The 2016-2018 Trek Madone was a fine rim-brake bike, but that bike would have been faster than the 2019 disc version. So Trek made the 2019 rim-brake bike slower as well, just so they can say that their disc-brake equipped bike is faster than the corresponding, same-year, rim-brake bike.

Irony here is that a rim-brake Cannondale would likely be faster than the disc-brake C'dale, but I don't think C'dale would be debuting that bike any time soon.

[vqdriver]

relax guys. everyone's had shower thoughts that withered in the light of day.

besides, we all know coaster brakes are the most aero.

[Mark McM]

out of all the new disc-brake equipped aero bikes, only the Cannondale seems to be worth the trouble.

Otherwise, manufacturers are contorting to get people to buy the disc-brake bikes. The 2016-2018 Trek Madone was a fine rim-brake bike, but that bike would have been faster than the 2019 disc version. So Trek made the 2019 rim-brake bike slower as well, just so they can say that their disc-brake equipped bike is faster than the corresponding, same-year, rim-brake bike.

Irony here is that a rim-brake Cannondale would likely be faster than the disc-brake C'dale, but I don't think C'dale would be debuting that bike any time soon.

This seems to be borne out by a recent Tour Magazine test of the latest aero bikes. A link to the test and a discussion of it can be found here:

https://weightweenies.starbike.com/forum/viewtopic.php?f=3&t=154692

Here's a summary of the results:

All tested at 45kph:

2019 Cannondale SystemSix Disc - 203w
2016 Trek Madone - 204w
2016 Specialized Venge ViAS - 204w
2016 Cervelo S5 - 205w
2016 Felt AR FRD - 205w
2019 Cervelo S5 Disc - 206w
2016 Canyon Aeroad - 208w
2019 Specialized Venge Disc - 208w
2016 Giant Propel Advanced SL - 210w
2016 Scott Foil Premium - 211w
2016 BMC Time Machine - 211w
2016 Look 795 - 212w
2019 Trek Madone Disc - 212w
2019 Ridley Noah Fast Disc - 213w

The aero road bikes from every manufacturer in the test got slower when they redesigned it for disc brakes, except for Cannondale. But even for the Cannondale, they redesigned and re-optimized the entire bike, so who knows whether redesigning and re-optimizing around rim brakes wouldn't be faster still?

I've read the Cervelo white paper on the S5 Disc, which claims that the S5 Disc is faster than the previous S5 (no surprise there - every manufacturer claims their new bike is better than their old bike). But if you look closer, you'll see that they changed many aspects of the design (such as routing all the cables internally through the special stem, headset and fork). They mention how much power each change saved, and it adds up to more than the power saved by the whole bike - which implies that switching from rim to disc resulted in a power loss, for which they had to redesign other parts to make up for.

[54ny77]

It's a good thing these bikes will have discs, since with all the improved aero on the frame it might require greater application of brake forces to stop while coasting to a red light . At 5-8 mph, the average rider needs confidence they can stop comfortably and safely, with plenty of margin for error.

[Ed-B]

....The whole purpose of an aero bike is to use them....where constant speed is high enough that the aero advantage of aero tubes offsets the weight penalty....caliper brakes would offer better aero gain than disc brake, as well as reducing overall weight.... But since everything in the bike industry is about marketing and forced gear retirement, the manufactures probably don't want you to know this.....

See, with a little editing, the theory in the original post is true, and the poster vindicated! (I just needed to clip out the parts about flat roads and relative braking performance.)


This seems to be borne out by a recent Tour Magazine test of the latest aero bikes. A link to the test and a discussion of it can be found here:

https://weightweenies.starbike.com/forum/viewtopic.php?f=3&t=154692

Here's a summary of the results:



The aero road bikes from every manufacturer in the test got slower when they redesigned it for disc brakes, except for Cannondale. But even for the Cannondale, they redesigned and re-optimized the entire bike, so who knows whether redesigning and re-optimizing around rim brakes wouldn't be faster still?

I've read the Cervelo white paper on the S5 Disc, which claims that the S5 Disc is faster than the previous S5 (no surprise there - every manufacturer claims their new bike is better than their old bike). But if you look closer, you'll see that they changed many aspects of the design (such as routing all the cables internally through the special stem, headset and fork). They mention how much power each change saved, and it adds up to more than the power saved by the whole bike - which implies that switching from rim to disc resulted in a power loss, for which they had to redesign other parts to make up for.

[ergott]

All tested at 45kph:

2019 Cannondale SystemSix Disc - 203w
2016 Trek Madone - 204w
2016 Specialized Venge ViAS - 204w
2016 Cervelo S5 - 205w
2016 Felt AR FRD - 205w
2019 Cervelo S5 Disc - 206w
2016 Canyon Aeroad - 208w
2019 Specialized Venge Disc - 208w
2016 Giant Propel Advanced SL - 210w
2016 Scott Foil Premium - 211w
2016 BMC Time Machine - 211w
2016 Look 795 - 212w
2019 Trek Madone Disc - 212w
2019 Ridley Noah Fast Disc - 213w

Unless these were all tested in the same session there's too much margin of error to be valid.

[echappist]

Unless these were all tested in the same session there's too much margin of error to be valid.

someone on slowtwitch independently stated (with evidence, though can't seem to find it right now), that the older Trek Madone was more aero. He expressly advised that I buy a new old stock Madone rim-brake when I was contemplating buying a new bike, stating that neither the newer rim-brake nor the disc-brake matched the older rim-brake. That was why this report resonated

[ergott]

someone on slowtwitch independently stated (with evidence, though can't seem to find it right now), that the older Trek Madone was more aero. He expressly advised that I buy a new old stock Madone rim-brake when I was contemplating buying a new bike, stating that neither the newer rim-brake nor the disc-brake matched the older rim-brake. That was why this report resonated

Okay that was said, but based on what evidence? Unless they were tested side by side in the same wind tunnel session it's inconclusive. Trek isn't going to spend time testing that (or publishing if that's the case). I doubt any privateer would spend the time/money.

[ergott]

Even if it was tested properly and the results were 8w I personally would prefer the disc bike. I tried the rim brakes on the Madone once and wasn't impressed. I sure as heck wouldn't want to service cable brakes on that bike either. Once installed, there's really no reason to ever go in and replace any of the disc brake system year to year.

[echappist]

Okay that was said, but based on what evidence? Unless they were tested side by side in the same wind tunnel session it's inconclusive. Trek isn't going to spend time testing that (or publishing if that's the case). I doubt any privateer would spend the time/money.

apparently Trek's own white paper

http://trek.scene7.com/is/content/TrekBicycleProducts/TK18_Madone_Whitepaper_EN-GB.pdf

note that the difference is well on marginal (1% faster for the older one), but this doesn't add all lend credence to the assertion that disc-brake frameset is faster

[Bonesbrigade]

Unless these were all tested in the same session there's too much margin of error to be valid.

All this tells me is that for each manufacturer the rim and disc versions are pretty damn close and not worth getting excited about. You are free to choose which version you want with basically no aero penalty.

As much as I love my rim brakes and don’t really see the point of discs on a pure road bike, I don’t think the big manufacturers will be putting much R&D into rim brake optimization. Almost all the world tour teams are on disc this season.

[ergott]

Final new Madone
numbers show an average of 3,216 g across a -12.5° to
12.5° yaw sweep vs the current Madone at 3,202 g. A 14 g
difference that is within Trek’s project goal and within a wind
tunnel’s experimental error band.

Within margin of error. That's not a clear difference.

Hey I'm skeptical that any of those bikes are significantly faster than my old Cervelo S2. I've got much smaller frontal surface area on this bike than the current fat tubes used.

https://photos.smugmug.com/Cycling/The-bikes/i-SszWgDb/0/8ddad974/L/20180926_200146-L.jpg

https://photos.smugmug.com/Cycling/The-bikes/i-wwTTWRL/0/c2d621e9/L/20180911_105748-L.jpg

[bikinchris]

Wait...how are these people up in arms over disc brakes, but they are okay with direct mount brakes?

[Bonesbrigade]

I would tend to agree with the S2 being hard to beat aero wise. I’m still using my 2008 cervelo SLC-SL and my my soloist team. They are both getting long in the tooth though.

[echappist]

Within margin of error. That's not a clear difference.


which is to say, we shouldn't trust the ad copy saying that disc-brake is faster

i don't know about your riding style and attributes, but i was the type to go for any little aero advantage possible back when I raced. I couldn't accumulate points from sprinting, so I had to get away solo or in a small group, and aero helps there.

The S2 was ahead of its times, and i'd venture that few framesets represent a significant upgrade over yours (earlier S5 being one of those)

only minor quibble is that you can save a bit more by using an aero road brake such as the Tririg Omega

[Mark McM]

Almost all the world tour teams are on disc this season.

I guess that's what the bike company marketers want you to believe (and it looks like you've been drinking the Kool Aid). But when this was discussed a few weeks ago, it was found that the majority of world tour teams are not using disc brake bikes (10 out of 18). Of the other 8 teams, 4 are using a mix of rim and disc brakes, and only 4 are using disc brakes exclusively.

https://forums.thepaceline.net/showthread.php?t=233038


I suspect that it has nothing to do with extra aero drag, and the reason racers use rim brakes instead of discs is similar to why they use tubular tires instead of clinchers:



By many measures clincher tires give a performance advantage over tubulars because clinchers have lower rolling resistance (and also often lower aero drag as well),

BUT:

The performance advantage of clinchers over tubulars is very small, and because clinchers are more prone to pinch flats and can't be ridden as fast when flat, the risk of losing a lot of time due to flat clinchers is of greater concern than gaining a little bit of time due to their lower rolling resistance.




By many measures disc brakes can give better braking performance than rim brakes, by giving more consistent brake performance over a wider range of conditions.

BUT:

The time gained due to the braking performance of disc brakes over rim brakes is very small, and because disc wheels are slower to change and disc brake wheels have more interchangeability issues, the risk of losing a lot of time with disc brake wheels in case of flat tire or other wheel problem is of greater concern than gaining a little bit of time due to their more consistent performance.

[Burnette]

relax guys. everyone's had shower thoughts that withered in the light of day.

besides, we all know coaster brakes are the most aero.

Coaster brakes were so rad!

[ergott]

which is to say, we shouldn't trust the ad copy saying that disc-brake is faster



only minor quibble is that you can save a bit more by using an aero road brake such as the Tririg Omega

Agree on both accounts. I'd say all these aero bikes are pretty damn slick compared to the old, round tubed bikes.

You can get very close to these car-priced bikes for a lot less.

I've been thinking about a more aero front brake for a while.

Sent from my SM-G950U using Tapatalk

[Bonesbrigade]

Ha, ha no kool aid here! I’m still happily using my 2005 and 2008 cervelos for road cycling. I could care less to be honest, but it doesn’t take a genius to see where this trend is going regardless of the actual number of teams using disc bikes right now.

I’ve seen this story play out in the bike biz with many changing standards over the years.

It’s clear to me that the majority of R&D is going into disc brake bikes and not rim brake bikes regardless how anyone feels about it.

[Hawker]

relax guys. everyone's had shower thoughts that withered in the light of day.

besides, we all know coaster brakes are the most aero.

I grew up in the 50-60s. All we had were coaster brakes and they seemed fine on our 35lb Schwinns, Murrays and Rollfast models. Then Bob got a 10 speed "English" bike around 1964. I'll never forget the first time I pedaled backwards to apply the brakes. Crap that hurt.

[Burnette]

Ha, ha no kool aid here! I’m still happily using my 2005 and 2008 cervelos for road cycling. I could care less to be honest, but it doesn’t take a genius to see where this trend is going regardless of the actual number of teams using disc bikes right now.

I’ve seen this story play out in the bike biz with many changing standards over the years.

It’s clear to me that the majority of R&D is going into disc brake bikes and not rim brake bikes regardless how anyone feels about it.

Exactly.

[sipmeister]

I found a video of Tom Ritchey on YouTube to be pretty informative. It's titled:

Tom Ritchey Q&A With fahrstil


He starts talking about aerodynamics and drag at about 42 min into the talk, but the whole clip was worth watching.


As a user of disc brakes, I couldn't imagine riding a mountain bike without them. That being said, my main challenge on a road bike is not slowing down, but going faster.

Finally, I will not rest easy until disc brakes come stock on balance bikes. Shoe life will be increased.

[mattsurf]

As more bikes become disc brake only, wheel designers will be able to play with the rim shapes to make them more aero, this is where a load of benefits will come

My own experience: I was riding my TT bike in Ironman Zurich (appologies to all Triathlon haters). Climbing Heart Break hill, supporters shower the riders with cool water, however, immediately after HB Hill, there is a short technical descent, I hit my brakes at 35-40mph to go into the first corner, my brakes and wheels were wet, it was clear I wasn't going to make it, so I bailed and went straight on, crossing a small traffic island, and mounted the sidewalk, luckily there was a dropped curb on traffic island and sidewalk for pedestrians. My next TT bike will have discs.

[Burnette]

As more bikes become disc brake only, wheel designers will be able to play with the rim shapes to make them more aero, this is where a load of benefits will come

My own experience: I was riding my TT bike in Ironman Zurich (appologies to all Triathlon haters). Climbing Heart Break hill, supporters shower the riders with cool water, however, immediately after HB Hill, there is a short technical descent, I hit my brakes at 35-40mph to go into the first corner, my brakes and wheels were wet, it was clear I wasn't going to make it, so I bailed and went straight on, crossing a small traffic island, and mounted the sidewalk, luckily there was a dropped curb on traffic island and sidewalk for pedestrians. My next TT bike will have discs.

I think it was Cervelo who determined that for the bike itself, the biggest factor for aero was the handlebar shape by far.

Tri shows that the rider and his/her position and clothing mean more than negligible losses below anyway.

I don't do Tri but I like the bikes and tech that go into them.

[Mark McM]

As more bikes become disc brake only, wheel designers will be able to play with the rim shapes to make them more aero, this is where a load of benefits will come.

I'll believe that when I see it. Many times potential advantages have been promised, and yet they never come to pass. We were told that tubeless tires would be lighter, have better traction, and lower rolling resistance, yet this hasn't happened. We've been told that disc brakes will allow wheels to be more aerodynamic, but this hasn't happened either. Exactly how do you imagine that rims can be reshaped for aerodynamics that rim brakes don't allow? Some have clamed that disc brake wheels don't need to have parallel sidewalls, which is true - but neither do rim brakes. I've got several sets of rim brake wheels with sidewalls (brake tracks) angled for aerodynamics.

This may be yet another case of counting your chickens before they hatch.

[Burnette]

It's old news and well known that by removing the restrictions that rim brakes held over wheel design it opened up possibilities that weren't there before.

Whether it matters a whole lot to many people is another matter.

[Mark McM]

It's old news and well known that by removing the restrictions that rim brakes held over wheel design it opened up possibilities that weren't there before.

That's just repeating prior unsupported claims. Well known by whom? Where's the evidence?

[Burnette]

That's just repeating prior unsupported claims. Well known by whom? Where's the evidence?

Relax. Rim brakes will be available on bikes for years, maybe not on certain brands or models, but they will be there.

We've all done this dance a hundred times.

[ergott]

We were told that tubeless tires would be lighter, have better traction, and lower rolling resistance, yet this hasn't happened.

Tubeless tires are at the top of the list. In general they are competitive in weight and rolling resistance while greatly increasing the chance a puncture won't stop you on the side of the road.


https://www.bicyclerollingresistance.com/road-bike-reviews

[benb]

I'll believe that when I see it. Many times potential advantages have been promised, and yet they never come to pass. We were told that tubeless tires would be lighter, have better traction, and lower rolling resistance, yet this hasn't happened. We've been told that disc brakes will allow wheels to be more aerodynamic, but this hasn't happened either. Exactly how do you imagine that rims can be reshaped for aerodynamics that rim brakes don't allow? Some have clamed that disc brake wheels don't need to have parallel sidewalls, which is true - but neither do rim brakes. I've got several sets of rim brake wheels with sidewalls (brake tracks) angled for aerodynamics.

This may be yet another case of counting your chickens before they hatch.

Hilariously there are lots of Walmart super cheap bikes with rim brakes that have angled rim sidewalls... it is not a cost thing.

This stuff tends to be a bit hilarious.. < 10w at 27mph. I can't TT at 27mph. I don't even race anymore. Not going to worry about it.

It seems the Pros aren't worrying a lot about a lot of it either when they keep choosing the rim brakes even when the discs are supposedly so much better, etc...

Even when you've got the guys at the razors edge at the top of the sport it so often seems like the races are determined not by these aero engineering items but whether a given rider has something going on with their back that prevents them from hitting the optimal riding position for aero, or whether another rider seems to have an attention issue and crashes.

Ignoring the dope they were both consuming no amount of aero advantage would ever have allowed Ulrich to beat Lance in the TdF. Lance had that back shape thing that hurt his aero probably more than anything Trek could have done to his bikes, but it didn't matter when Ulrich failed to keep the rubber side down so many times.

As for tubeless I think all those claims have borne out on the MTB side.. I think if we all changed our mind and were clamoring for tubeless road it would spur enough R&D the tubeless tires would start improving more rapidly. Chicken and Egg?

[ergott]

The biggest reason for a pro to skip disc brakes right now is the thought of trying to get a spare wheel in a race. The other stuff is minuscule in comparison.

[EDS]

I'll believe that when I see it. Many times potential advantages have been promised, and yet they never come to pass. We were told that tubeless tires would be lighter, have better traction, and lower rolling resistance, yet this hasn't happened. We've been told that disc brakes will allow wheels to be more aerodynamic, but this hasn't happened either. Exactly how do you imagine that rims can be reshaped for aerodynamics that rim brakes don't allow? Some have clamed that disc brake wheels don't need to have parallel sidewalls, which is true - but neither do rim brakes. I've got several sets of rim brake wheels with sidewalls (brake tracks) angled for aerodynamics.

This may be yet another case of counting your chickens before they hatch.

As far as aerodynamics for disc only wheels, since you no longer need a flattish brake track could wheel designers more fully optimize the shape of sidewalls to improve wheel/tire intersections from an aero perspective?

I do not know if the above is possible, just asking the question.

[Mark McM]

Tubeless tires are at the top of the list. In general they are competitive in weight and rolling resistance while greatly increasing the chance a puncture won't stop you on the side of the road.


https://www.bicyclerollingresistance.com/road-bike-reviews

I think you mean A tubeless tire is at the top of the list. This particular tire is also very lightweight and notorious for being delicate and flatting easily. (It's also not a true tubeless tire - instead it is Tubeless Ready.) There is no standard tubed version of the Vittoria Corsa Speed TLR to compare it to, so we can't know if it would be even better in a standard tubed version. But if you did a careful comparison of otherwise similar tires (i.e., similar size, tread thickness and casing toughness), I believe you'd see that tubeless tires show no clear advantage over standard tubed tires.

Another comment on the www.bicyclerollingresistance.com tests: These tests are a bit biased against standard clinchers, as their test procedure uses a relatively thick and lossy tube, not a low rolling resistance tube. Another test on this site show that latex tubes or thin butyl tubes will lower rolling resistance substantially, but they have chosen not to do tire tests with these tubes. Other testing groups that that do use latex tubes have shown that with these tubes, tubeless tires generally do not have lower rolling resistance.

[Mark McM]

As far as aerodynamics for disc only wheels, since you no longer need a flattish brake track could wheel designers more fully optimize the shape of sidewalls to improve wheel/tire intersections from an aero perspective?

Maybe, but it hasn't really been demonstrated yet. Also, it should be noted that flat, parallel brake tracks on rims is a relatively recent innovation (just the last couple of decades). Before that, rims commonly had curved and/or angled sidewalls. There were even some rims with concave sidewalls.

Here's a popular rim from the 1980's, the Campagnolo Lambda Aero:

http://www.bikepro.com/products/rims/rims_jpg/lll_lambda_v_section.jpg

And even though sidewalls are typically flat today, not all of them. Here some more modern Zipp rim brake wheels - which are clearly angled and curved for aerodynamics:

http://zipp.com/_media/images/dynamicproducts/RimProfiles.jpg

https://c1.staticflickr.com/7/6084/6100156377_7c36704353.jpg


Would these rims be shaped differently for disc brakes?

[ergott]

I think you mean A tubeless tire is at the top of the list. This particular tire is also very lightweight and notorious for being delicate and flatting easily. (It's also not a true tubeless tire - instead it is Tubeless Ready.) There is no standard tubed version of the Vittoria Corsa Speed TLR to compare it to, so we can't know if it would be even better in a standard tubed version. But if you did a careful comparison of otherwise similar tires (i.e., similar size, tread thickness and casing toughness), I believe you'd see that tubeless tires show no clear advantage over standard tubed tires.

Another comment on the www.bicyclerollingresistance.com tests: These tests are a bit biased against standard clinchers, as their test procedure uses a relatively thick and lossy tube, not a low rolling resistance tube. Another test on this site show that latex tubes or thin butyl tubes will lower rolling resistance substantially, but they have chosen not to do tire tests with these tubes. Other testing groups that that do use latex tubes have shown that with these tubes, tubeless tires generally do not have lower rolling resistance.

Top 2 tires are tubeless. Next in line is tubular. The top clincher isn't an everyday tire either. When factoring in a latex tube as they suggest in more detail in the reviews the clincher would perform along side the tubeless tires. Keep in mind people with carbon clinchers and rim brakes are advised not to use latex tubes. This segment of the market (the ones that care most about these details) is more likely to own carbon wheels so you can assume they can use latex tubes.

Bottom line, like the brake arguments here you can't say one is a clear winner and you should just buy what works for you. To say that tubeless tires are at a distinct disadvantage to clinchers hasn't been the case for quite some time now and there have been great improvements in tubeless tires especially in the last 2-3 years.

[zmalwo]

I assume a lot of the pros choose rim brakes to save weight. Contador used mechanical groupo until very recently IIRC to save that 200g of weight on mountain stages. When you have to climb 3 everest mountains every grand tour, the lightest bike is the way to go. I assume the same for aero bikes, i have not seen 1 aero bike in any size that's even close to 6.8kg. Until disk brakes become lighter than rim brakes, pros are going to stay with rim brakes.

[Mark McM]

Bottom line, like the brake arguments here you can't say one is a clear winner and you should just buy what works for you. To say that tubeless tires are at a distinct disadvantage to clinchers hasn't been the case for quite some time now and there have been great improvements in tubeless tires especially in the last 2-3 years.

Which is of course why I never claimed that tubeless tires are a distinct disadvantageous (for rolling resistance). As I think we've both shown, they are roughly on par, with no clear advantage one way or the other. But that's not what has been claimed in the past - many people promised that tubeless tires would be better.

There have been many claims about disc brake bikes/wheels having an aerodynamic advantage. We may have to wait a bit more for definitive data, but from what we know so far, they have not yet proven to have the distinct advantages claimed.

[ergott]

Both disc and tubeless for performance road are in their relative infancy. Seeing how fast there have been legitimate development tells me we haven't reached any sort of peak. You can't integrate rim brakes into the frameset like you can disc. The ones that have tried (Trek, Specialized, Ridley) have had relatively poor performing caliper brakes. Tubeless tires have gotten significantly more supple and better performing in the last couple of years. The difference between my current Schwalbe Pro Ones and the first Hutchinson Fusions I had is big.

[Mark McM]

Both disc and tubeless for performance road are in their relative infancy. Seeing how fast there have been legitimate development tells me we haven't reached any sort of peak. You can't integrate rim brakes into the frameset like you can disc. The ones that have tried (Trek, Specialized, Ridley) have had relatively poor performing caliper brakes. Tubeless tires have gotten significantly more supple and better performing in the last couple of years. The difference between my current Schwalbe Pro Ones and the first Hutchinson Fusions I had is big.

"Fusion power is the energy source of the future - and always will be".

"Where's the my flying car?"

I don't make equipment decisions based on promises for the future, I make them on current performance and characteristics.

[Burnette]

You know can check all wheel sellers sites that offer disc for said info, trying to argue it out backwards here is a bit of a waste.

[Bonesbrigade]

I don't make equipment decisions based on promises for the future, I make them on current performance and characteristics.

A current performance went down today at the tour of Columbia. The top 2 teams in the TTT were on disc brakes. EF actually won a TTT!

I am by no means saying they won because of disc brakes, my main point is they are putting all the R&D money into disc brake system design, and the best current ones are already very good.

[54ny77]

Can we get back to doping while testing for aerodynamics?

[Burnette]

Can we get back to doping while testing for aerodynamics?

Exactly, we're just rehashing disc thread stuff that we've all done to death. To summarize this thread: ride what you like and let the riders around you do the same.


The search for "proof" of anything requires testing.
For real world testing in real time we have to dope and ride vigorously and for long periods. Which I'm sure we'll forget to collect data on the first go around, cause short term memory loss, so then the retesting phase begins after that.

[54ny77]

Who said anything about riding vigorously, or riding at all?

:D

Exactly, we're just rehashing disc thread stuff that we've all done to death. To summarize this thread: ride what you like and let the riders around you do the same.


The search for "proof" of anything requires testing.
For real world testing in real time we have to dope and ride vigorously and for long periods. Which I'm sure we'll forget to collect data on the first go around, cause short term memory loss, so then the retesting phase begins after that.