Cyclocross - front braking and vibrations
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My wife surprised me with a new bike this past week! It's a 2012 cannondale superx. It's my first carbon fiber bike. It has a super nice ride compared to the hybrid I was ride. I've noticed that with moderate to heavy front braking bike develops bad vibration. The vibration gets worse when using a combination of rear and front brakes. No vibrations occur if using only the rear brakes. I've tested on various road surfaces so it's not the road. The vibration occurs at all speeds. It feels like the vibrations are coming from the bottom bracket. Any clues are to what is going on? Combination of EuroTRP/Mavic Kysrium Equipe wheels? I'm going to call the LBS tomorrow. But, would like some info before I talk with them.
10-29-12, 09:55 PM
Its the headtube mounted brake cable stop that is most likely causing the problem. Carbon forks seem to magnify the problem.
From Lennard Zinn
What happened is that the fork blades and your headtube flexed. Just a little but enough to change the distance between the brake cable stop and the brake arms. This caused the brakes to pull harder. Something had to give, either the tire will skid, the brake pad will skip, or you'll go over the bars and crash. In this case the brake pad skipped on the rim. That released the pressure momentarily the frame and fork flexed back then the pad caught again and the process repeateded. The whole process happens very quickly, many times a second.
Without a fork mounted cable stop there a limited option. Toe in the brake pad, use short pads. Check the canti brake sticky in the cx forum for more info/help.
I switched to mini v-brakes. Problem solved. Wasn't going to get rid on my ritchey wcs fork for one that has a fork mount.
Ehh... I really didn't, or wouldn't, expect this type of problem with a new bike. How easy is it to toe-in canti brakes? I refuse to replace parts on a new bike.
10-29-12, 10:57 PM
pyze-guy gave you the correct advice. Proper canti brakes use fork-mounted cable stops. Cable-stops mounted above the head tube are dangerous junk that are unsafe on anything over an 8% grade. In my case I learned the hard way that descending 14% grades with 200 pounds total weight resulted in an unusable front brake because it locked every time I touched it. Toe-in adjustment did nothing. Installation of a fork-mounted cable-stop solved the problem.
10-30-12, 06:18 AM
Ehh... I really didn't, or wouldn't, expect this type of problem with a new bike. How easy is it to toe-in canti brakes? I refuse to replace parts on a new bike.Google "cantilever brake shudder".
The Super-X is a race bike built for performance, not for consumer convenience.
10-30-12, 07:59 PM
I had the same problem. I fixed it by placing a dime under the leading edge of each pad. I used a Velcro tie to hold the front brake lever. I then slightly loosened the break pad and re-tightened. What i was looking for was to ensure that the front edge of the pad did not dig in. Works perfectly, now.
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