Bicycle Mechanics - Disc break periodic gripping

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Wagh
07-11-10, 02:29 PM
I've got a little problem with my disc brakes. Bought a Giant Seek 2 recently with disc brakes, and both the front and back brakes have a periodic sticking. Once per revolution they grip more than they do otherwise. Needless to say, this makes braking inconsistent and annoying. Any idea what the problem is? I brought it in, and the guy who took a look at it said he didn't know how to fix it, but it sounds like a totally fixable problem.

Edit: Brake...not break...whoops.

FBinNY
07-11-10, 03:02 PM
If they're pulsing under when applied it's related to the rotor (disc) which might be warped, have a ding, or have some surface contamination which causes the friction to differ in various areas. Check the rotor, and clean, straighten or replace it as necessary. (search clean disc brake rotors for cleaning tips)

If the brake is occasionally sticking or rubbing when not applied, it's either a bent rotor, or the caliper itself isn't releasing completely, and the possible causes differ depending on whether they're hydraulic, or cable activated brakes.

My best quick guess is a dirty rotor, BTW- any decent mechanic with the bike in his hands should be able to diagnose the problem and suggest the fix. I'd consider finding a new mechanic along with working on the brake problem.