Pad Orientation to Reduce Squealing
I realize this reply is about 10 years too late, but I recently found this thread useful in trying to solve squealing on my rim-braked G29.
I started with an anodized Surly Rabbit hole rim (a great modern tubeless comaptible rim that is rim brake compatible) and a Triton triple frame with a magura rim brake.
Build Details here:
Squealing was so bad I could feel the vibrations in the seat.
Sanding the anodization off of the rim, and sanding the pads slightly (suggested in this thread) reduced the squealing a lot, but not completely.
After much trial, error, and bitter cursing I stumbled upon a solution to the squealing - pad orientation.
I found that if the pads were perfectly parallel to the rim at center of the pad then the squealing would stop.
In other words, If the pads were angled so that the front was even slightly higher up the rim than the back (or back higher than the front) the pads would squeal.
Hopefully this will help any of you rim brake hold-outs still out there.