Originally Posted by
sweeks
Brake squeal as I understand such things results from one or both brake arm assemblies resonating while under braking load. The objective is to change the system in some way to move the resonant frequency out of the range encountered in normal operation. One thing I've (apparently) had success with is using a thick (eg wheel-bearing) grease on the pivot bosses. If there has been enough wear to allow "rocking" movement of the brake arm, the grease may provide some damping. Might be worth a try.
(Greetings from Mundelein!)
Greetings from Ann Arbor!!!
Source of the vibe seems (at least I like Jobst Brandt's argument) to be a surface wave on the rubbing surface of the brake pad. Toe in was (I think) intended to limit the vibrating surface. I don't know if there is play in my canti pivot bearings. Plan is to set the shoes square with the braking surfacs (machined) and send her out to try it. I did that work and I can't make it squeal, but she seems to have a knack for it. I think tomorrow I"m going to set up the toe-in, since I think I figured out a way to do it without a helper - use an old toe strap to force the calipers closed over the popsicle stick or other wedge, loosen the clamps, and force the brake lever with the toe strap, tighten the brake shoe clamp bolts, and release the toe strap. If its all still aligned correctly do the other brake and go out and ride. We'll see. If that doesn't work overhaul the calipers and measure the outer journal and inner and see if there is any play. I don't expect any, these have less than 2000 miles on them and I put Park grease in when I installed them.
I might also try several different gaps, or even asymmetrical gaps, as somebody else selected. But this begins to sound more like research than repair!
I think I've had that old toestrap in my toolbox since we rode around Evanston together!