Originally Posted by
Kontact
The fact that you found a bike with a wheel resonance issue does not mean that askew calipers can't also cause squeal.
When a caliper is canted off the plane of the disc, the disc has to change shape as it passes through the pads under braking. That is more than enough to also make that contact sing. (We are talking off-parallel, not off-center.)
I don't know what is causing the OP's problem. But I have solved enough brake squeal on uncontaminated parts by carefully aligning the caliper that it is something absolutely worth checking. And the prevalence of the "hold the brake and tighten the bolt" advice is enough to make me wonder if all shop mechanics are savvy enough to avoid doing that. So I would recommend the OP puts a piece of paper on the floor and look through his brake gap to see if the pads are nice and parallel to the rotor before they buy any more stuff. You can put the paper back in the printer when you are done, so there is no cost for performing this check.
I've seen more than one official maintenance manual outline that exact procedure for lining up the calipers. SRAM was one of the offenders. Lining up manually by eye is something I haven't seen in a maintenance manual ever. Then again it's been a few years since I read about lining up calipers. But it could be that some mechanics go with the bad info they get in tech docs because it's convenient and they can claim it's official.
But another trick on the same vein is adjusting pistons manually. Sometimes one of the pistons is a bit dominant or more protruded, which can cause the pads to twist the rotor slightly when braking. That can cause noise or be felt as vague bite point. The way to correct that is to put s small screwdriver behind the non dominant pad (not between the piston and the pad!), and push the pad towards the center whilst simultaneously slightly pulling the brake lever. This should push the dominant piston back a bit and allow a more even contact.