Bicycle Mechanics - disc brake squeal

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Tried cleaning pads/rotors,squeal eventually returns
reptilezs
03-26-11, 04:52 PM
way too many factors to diagnose over the internet. for me proper bed in is the first line of defense
fietsbob
03-27-11, 10:12 AM
Tried cleaning pads/
With what? you should just replace the pads,
'cleaning' will just contaminate the friction material.
slide23
03-27-11, 02:59 PM
What I have found with stubborn disc squeal is that the pads are usually irretrievably scorched. I always use the same brand pad on all my disc bikes (Delta Aztec sintered). As long as the pad never gets overheated, I can run them down to the point where the pad spring gets pulled into the rotor, and never get a squeal. But a scorched pad will never stop squealing.
Replace and upgrade your pad.
Also, double check the alignment of the calipers. If you're running Avid brakes, just run through the alignment process.
Thanks,what would you recommend for an upgrade for a Hayes 98-20197?
slide23
04-04-11, 01:14 PM
I'm not ignoring you; I just have no clue what works best with Hayes.
Woodwind314
04-05-11, 07:48 AM
I don't know if this will work with disc brakes, but with squealing / chattering rim brakes there is a 'magic' cure:
Clean rim and pads. Then spread a tiny amount of motor oil on the rim with your fingertip. Just a few drops.
Do a bit of test braking. At first, you'll hardly get any braking power. After 5-6 attempts, braking power comes back - minus the squeal.
slide23
04-05-11, 08:50 AM
Clean rim and pads. Then spread a tiny amount of motor oil on the rim with your fingertip. Just a few drops.
Uh, don't do that. At best, you will contaminate the disc pads as they are porous. At worst... well, think about it.
Woodwind314
04-05-11, 02:09 PM
Uh, don't do that. At best, you will contaminate the disc pads as they are porous. At worst... well, think about it.
As I said, I don't know if it works with disc brakes. Works like a charm on rims...
Thinking about automobile brakes, a little oil or grease on the brake pads is not problematic. At worst, you get some burnt oil smell the next time you brake hard.
The idea behind the oil trick is that brake squeal results from slip-stick. Or rather, from a large difference between the stationary (stick) friction, and the sliding (slip) friction. The oil decreases stick friction much more than slip friction, at least between rubber pads and aluminium rims.
It might work with other material pairings as well.
greyghost_6
04-06-11, 02:08 AM
Some disc brakes are just squeaky no matter what you do to them (in my experience). What I used to do is lightly sand the rotors and dust off with rubbing alcohol swabs making sure not to brake during the cleaning and contaminating. Also maybe the calipers are not "clapping" on the rotor parallel to each other. Probably time for new pads and a good adjustment.
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