Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Mentioned: 20 Post(s)
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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.
An ounce of diagnosis is worth a pound of cure.
“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin
“One accurate measurement is worth a thousand expert opinions”
- Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance