Originally Posted by
TiHabanero
Kontact, as a former shop mechanic for almost 40 years, I agree with you. Centering of the rotor in the caliper has nothing to do with a vibration problem.
I had a Specialized road bike with an unsolvable squealing front brake problem. Fortunately for the owner, the bike was under warranty. Specialized immediately pushed the problem onto Sram, and Sram, being the saints that they are, willingly took on the issue and we replaced the entire front brake system, including the lever. No solution.
Installed a front brake from the same model that we had in stock. No solution.
I then took a wheel off of a Giant road bike and put it on the Specialized and this solved the issue. The wheel was the problem, not the rotor, not the pads, not the caliper, not the fork, not any other part of the bike. It was the wheel.
Next i took a wheel off a Specialized road bike and had brake noise. I then took an aftermarket wheel of higher quality and the problem went away. At this point I informed Specialized of all this and convinced them to send out a replacement wheel set that was one level up from the stock Roval that came on the bike. This solved the issue. Something about the stock wheel was a problem. Sent it Specialized and they did who knows what with it.
This experience had me change my tune about Sram, they are in my good graces now, and it confirmed why I prefer rim brakes for my own bikes.
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.