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My commuter bike's disc brakes keep on going from fine for a few days to making a ridiculous squeal and it's driving me nuts 👿
The setup is Deore M615's with 160mm RT66 discs. Tried Shimano pads (resin and sintered) and various aftermarket varieties from the usual suspects and they all do exactly the same thing. I bed them in correctly so that the power is there, they work for a few days but then they start to lose power gradually then the noise starts. I have checked for leaks, even switched the brakes over with another bike (which has the same brakes) and the problem stays with the bike so it's not a seal issue. Even put the squeaking pads on the mtb as-is and they wok fine after a few muddy puddles! The one thing I have noticed is that the disc and pad surface look like a mirror once the noise starts. Rough them up and re-bed them and the problem goes away but is back a few days later.
My commute is 4 miles each way and completely flat (40ft of hills total) so the brakes never get up to temp just stopping from 15mph for traffic lights. This makes me think it's not glazing but the pads and discs polishing up?
Has anyone had similar? Thinking getting some cheaper discs and new pads might solve it as the previous commuter bike had Shimano resin pads but with cheap Tektro discs and had no issues on the same route.
SQUUUUUEEEEAAAAAKKKKKK!!!! 🙁
This makes me think it's not glazing but the pads and discs polishing up?
That's what I would consider "glazing", the pads aren't being given enough to do and the surface is being polished by the disc.
Extend your commute to include some hills. 🙂
I found the Shimano resin pads much quieter than the metal one's.
Could you try smaller rotors? Or brake later but firmer?
Running the smallest rotors I can so going smaller is not an option. The shim another resin pads do last the longest before going noisy but it's in 2-3 days. Already doing the late braking thing to no avail. As for hills that would mean a 5 mile detour!
Would something like one of the lightweight rotors bite into the pad harder and scour the pad surface?
To get effective braking performance the pads will need to deposit a small amount of their compound material over the minuscule imperfections in the disk surface - when the pads contact the disk surface the deposited pad compound material will heat up due to friction and ensure the pads [i]bite[/i].
Put up with the squealing for a while and they should eventually settle down or find a long hill and do a set of 5-10 reps down the hill at a reasonable speed whilst applying the brakes to heat up the pads/disk surface till the pads transfer a suitable amount of material on the disks.
I bed them in already using a big hill and they have loads of power for 2 days then they go from perfect to foghorn over the next day's return trip. Sanding and resending them gives the same result. I always thought glazing happened when you drag the brakes getting them hot but not enough to bite? If the constant stop-start is going to glaze them regardless then maybe discs aren't the best braking option?
Try cutting off half the pad compound. Then what's left will have to work harder and get hotter.