ArgoMan

Hey all. I invite your thoughts on using carbon wheels with rim brakes. I have been on an endeavor to build a new CRIT bike and posted lots of queries here. But alas, I just had a huge financial burden unexpectedly hit me and need to put the project off. BUT, I already have a pretty nice aluminum frame in the form of an older "Motobecane" (Bike Direct) 7005 aluminum frame "Record" model. I took it out this weekend and was really surprised at how stiff it is and how well it accelerates. I have a set of cheap "SuperTeam" carbon wheels on it. Not too light for carbon, but surprisingly stiff. I used the bike to just speed around the neighborhood. But I'm advised that using rim brake on direct carbon wheels is a no-no. The wheels are total carbon, so the brakes apply directly to a carbon surface. I saw a video from a carbon frame expert wherein he opines that the rim brake will wear at the carbon quickly and make it unsafe at some point, maybe when I'm not expecting a failure. The bike breaks just fine for my basic needs, but maybe not for repeated applications when going fast. But what are your thoughts on this topic? Any suggestions? Thanks!

datlas 

Carbon Fiber rim brakes are an option but they have limitations. Braking is not as good as with aluminum. Braking in the wet is especially bad. Not good for really long descents as they can overheat and pop a tube.

That said, they may likely be lighter and more aero than their aluminum counterparts, so worth considering. Like most things, it depends on your goals, circumstances, and budget.

If you get CF wheels you really MUST use carbon specific pads and not go back/forth with those pads between CF and aluminum braking surfaces. That would wear out the CF brake track super fast.

FWIW I run CF rim brakes May-September and aluminum October-April. Swapping out the pads is a minor annoyance.

ArgoMan

Thanks. I thought that there might be pads specific for carbon wheels. Any suggestions are to some good pads?

urbanknight

There are many (just make sure they say they are for carbon rims), but Kool Stop Carbon Red and Swiss Stop Yellow are favorites.

tomato coupe

Almost any brake / wheel combination will work for crits.

popeye

Black Prince are the go to pads for carbon.

chaadster

I was worried about this too, but my carbon fiber Lun Hyper wheels brake just fine with ths supplied pads, and they suggested Swiss Stop Black Prince when the time comes for replacements.

For reference, I’m 240lbs using Campagnolo Chorus sidepulls, and the braking power has been impressive, down hills and through rain. Honestly, I don’t notice a tremendous difference compared to aluminum rims, except for a little less aggressive initial bite.

I haven’t crit raced these, but I did alu rims and cannot think of any time during my two year crit racing “career” that I thought about my brake performance, so I think the CF rims will do just fine, too.

I’m not saying I’d drop down a moutainside on my CF wheels, but heading down a .5mi 6% decline in the rain is something I’ve done without issue and will do again, so it depends on how you ride. One can heat heat up the resin to its glass transition point, and that’s not good, but up until that point, they will work fine. I cannot say when you’ll hit that point, but for me as a heavy rider in rolling and moderately hilly terrain, it seems not to be an issue.

tFUnK

Just use the right pads, it seems like it shouldn't work but it works fine. Not the best design given the materials but carbon rim brake surfaces have come a long way over the past decade. I admit I do compensate my braking behavior riding down steep, prolonged descents, but I don't ride in wet conditions and so far have not had any issues with carbon rim brakes. Some pads work better than others. I've not tried them all but I like Reynolds Blue pads over the cheap cork ones.

daviddavieboy

I used a couple different types before I tried Bontrager branded cork pads on my HED wheels. By far these were the best in dry but never tested in wet conditions. I used them as well on my Bora wheels and they don't seem to be as good for some reason. Both are full carbon wheels and both dual pivot campy calipers.

Jrasero

I think if you are building a crit bike especially with parts you already have using carbon rim wheels is fine. Ideally a carbon rim wheel make zero sense IMO since literally you are degrading the carbon tracks and run the chance of delamination, thus wheels becomes disposables like chains or cassettes. For crits, rim brakes matter but not as much as descending, so yeah I think you are fine

chaadster

aluminum wheels wear out the brake track, too, so that carbon does is not a decisive factor.

Jrasero

they do but at much slower rates and also without catastrophic failure. IMO more of reason not to go rim period, but not to make this a rim vs disc debate

SoSmellyAir

In my experience with (Shimano 105 BR-5800) rim brakes in the dry, SwissStop Black Prince on (high TG) CF wheels stop about just as well as Shimano R55C4 on aluminum wheels, but the former squeals much more loudly.

chaadster

What are the comparative wear rates? I cannot recall of hearing of a carbon rim failing from wearing away of sidewall material, but it's certain that if an aluminum sidewall fails, particularly on the front wheel, it could definitely be catastrophic:


worn aluminum brake track blowout

I have aluminum rims with brake track wear indicators, and I take them seriously.

Jrasero

I have heard and seen plenty of carbon rim wheel delaminating, no they didn't catastrophically implode but at that point they needed to be repaired or binned. I also see a huge amount of carbon rim wheels where the brake track material wear down to the point where it come smooth, thus brake efficiency was crap and in wet conditions it simply was to dangerous to ride

Jrasero

btw this photo is of a tube exploding on a rim brake wheel. The big difference is that even with overuse the rim stayed in tact even though there was a blowout, but with a carbon rim that's overused and starts to delaminate the whole wheel would come apart in an even more catastrophic way. Secondly while that wheel was badly worn it still probably and more stopping power than a carbon rim wheel with worn brake tracks, since carbon wheel with no brake tracks is like trying to stop on ice


https://bicycles.stackexchange.com/q...e-blew-the-rim

datlas 

I suspect that CF brake track wear and/or failure is related to user error (using brake pads that have been on aluminum surfaces) rather than an inherent defect in CF.

I have zero evidence, however. But hey, this is BF so we can say what we think. Right?

chaadster

Carbon fiber delamination is probably caused by overheating, and is not necessarily or exclusively a characteristic of wear.

I also don't understand how CF brake track wear would become smooth; I'd expect that as the resin wears through, the fibers become exposed and the surface rougher. The fiber matrix is simply more coarse by its very nature than the uniformly textured (i.e. smooth) resin which is injected to keep it all together and rigid.

chaadster

No, what you are looking at in that picture is the aluminum brake track split away from the rim. I mean, of course the tube would burst when the sidewall lets go, but the brake track broke because it was worn thin and unable to retain its shape and integrity.

ArgoMan

Thanks for all the info. I think I'm going to keep the carbon wheels with rim brakes and just get some Kool Stop pads that are geared toward carbon.

SoSmellyAir

I am a late adopter to rim brake CF wheels, having bought my first CF wheelset only 15 months ago. From what I have read, brake track delamination is much less of an issue nowadays with the advent of high glass transition temperature (Tg) resin and brake shoe materials developed specifically for CF wheels. On some CF wheels, the brake track is also textured by either (1) laser etching the resin off to expose the underlying carbon fibers (Mavic) or (2) adding particles, e.g., basalt, graphene, etc. In the former, one might expect the brake track to remain coarse with wear, but not in the latter.

Germany_chris

I have no problem with my carbon wheels and Koolstop pads.

Sy Reene

I'd go Swisstop, I can't state this with certainty, but as an OEM maker, I think this page means that a lot of wheel makers use their product:
https://www.swissstop.com/about-swis...carbon-wheels/

chaadster

yes, exactly my understanding as well, except that in the case of a brake track textured with particulate— i.e. in the surface layer— by the time the rim integrity is compromised, that would mean wear through the particulate later, through the resin, and down into the fibers, which as we said are coarse (of necessity).

beeballman

I purchased Roval CL50 carbon rim brake wheels almost three years ago. I use the recommended brake pads - Swiss Stop Black Prince - In the three years I have had them I have had zero issues with them, and the brake track still looks as good as new. Now I am very obsessed with also wiping the bike and wheels down after almost every ride to check the rims. These wheels were worth the money and have been awesome with zero issues.