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Old 05-01-09, 10:20 AM   #1
Psimet2001 
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Tech Question - Brakes - Carbon Wheels

OMG...yes, I am asking a tech question. Not only do I not know the answer to this I actually feel like this is the best place to ask it.

OK...I have little experience with racing/riding carbon wheels. What experience I do have has been with clinchers that has aluminum braking surfaces. I bought a carbon tubular front wheel late last year for a steal off of the bay. My intention was to always use it for TT's

So...I have a TT on Saturday. I have not really ridden the wheel, but it's in great shape. The TT is not a critical event so I don't mind riding the wheel there for the first time. My big question is that I was always under the impression that I would most likely need to swap out the front pads to ones meant for carbon.

I contacted my shop/team owner who said that I did not. I could run the pads I had with no problems. Intuitively I know he's right. I figure I should remove any AL bits in the pads before doing it.

My guess is the reason you use the carbon specific pads is to gain better braking performance and better durability and heat dissapation. So by using my regular pads I can expect them to not have great performance and to have a much shorter life (?).

It's a flat TT. No descending, big braking situations, etc. I can probably just get away with using the rear brake only if I need to....

....but I am also looking more long term. Should I just stick with my pads or should I go out and get some carbon specific ones. These will only be used during TT's and I will probably do 5-10 this year.
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Old 05-01-09, 10:23 AM   #2
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correct.

Quote:
source.

Do I really need these?

Dear Lennard,

I recently heard that there is no performance benefit to using carbon-specific brake pads with carbon race wheels. The only real benefit that I was toldto using special brake pads is they last longer compared to using regular brake pads with carbon wheels, which doesn't seem like that big of deal(since I only use my race wheels maybe six times a year), and all I would have to do is replace my brake pads more often.Is this true? Are there any other benefits to using special brakepads with carbon wheels?
Aron

Dear Aron,
I can say from personal experience that standard brake pads on carbonrims are grabbier, giving louder, less predictable, potentially dangerousbraking, and they wear faster, even melting down rapidly at a criticalmoment on a long, fast, tortuous descent, leaving you with no brakes atall. Furthermore, conventional pads on carbon rims are downright scary in the rain, making for unpredictable braking until the rim is wiped clear of water enough for them to grab.

Lennard


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Old 05-01-09, 10:48 AM   #3
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Depends on the pads and the wheels...
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Old 05-01-09, 10:51 AM   #4
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btw - make sure it's not raining.
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Old 05-01-09, 10:52 AM   #5
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Quote:
Originally Posted by Psimet2001 View Post

....but I am also looking more long term. Should I just stick with my pads or should I go out and get some carbon specific ones.
You’re going to have the wheel for a while so just get the right pads for it.

Cheaping out on consumables after purchasing expensive equipment is just wrong.
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Old 05-01-09, 10:58 AM   #6
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You’re going to have the wheel for a while so just get the right pads for it.

Cheaping out on consumables after purchasing expensive equipment is just wrong.
I agree wholeheartedly. This was just a short term issue for the most part. I didn't have a job and could not justify getting the pads a while back. I just started back to work this week and have the TT on Sat but didn't think abot it until yesterday.

Then I called the shop owner who basically said, "don't bother".

FWIW it's a Zipp 404 front tubular pre-2006.
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Old 05-01-09, 11:36 AM   #7
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Since it is a flatt TT you probably won't do much braking anyway and you won't need high performance braking, so you could just file down a layer of your current brake pads and use them this weekend, and order some Swiss Stop yellows from Wiggle or something when you have the money to spend $45 on brake pads.
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Old 05-01-09, 03:18 PM   #8
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At the advice of UMD and others here, I picked up SwissStop Yellow pads; got them from Excel Sports for $39.95.
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Old 05-01-09, 03:25 PM   #9
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if you're up for buying more than you need, then this is the place.
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Old 05-01-09, 03:33 PM   #10
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I run my standard brake pads with my carbon wheels all the time. They are definitely grabbier but its really not that bad.

For a flat TT, I would not waste 5 minutes of my life switching pads over.
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Old 05-01-09, 03:48 PM   #11
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From what I understand, on an aluminum wheel (not CF with aluminum braking surface), heat is dissipated into the rim which acts as a big heatsink. In a CF rim (and, notably, CF rims with Al braking surfaces, which is why the Al surface sometimes comes unlaminated), the polymer in the rim doesn't dissipate heat all that well, so most of the heat is dissipated into the brake pads. When CF wheels first came out, people were using cork, which simply had less stopping power so less total heat was dissipated. Now, I think the brake pad material is more heat conducting and more thermally stable so you can keep your braking power and brake longer and harder without the brakepads melting or glazing or whatever they do when they overheat.

This is from my background in thermal management as a mechanical engineer and what I've learned by poking around this subject, not any experience with CF wheels. CF wheels only really work, I think, because brakes aren't used all that much in road biking and especially racing. Most of the time it's either hard braking for very short durations (corners and such), or feathering, both of which don't involve much total thermal energy.
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