Originally Posted by cachehiker
I then found the right set of brake shoes. Salmon Kool Stops did the trick for me. Their black ones were actually a step back from the Shimano pads. The severe conditions pads are a bit harder and tend to raise the resonant frequency of the brake arms/pads. I also toed them in about a "penny's worth" more than the Kool Stop instructions recommend.
Did you try toeing in the black Kool Stops that much? That additional toe-in may be the main reason why the salmon ones worked better for you. I spoke directly to the technical information department at Kool Stop, and they are the ones who confirmed that the black compound is less likely to squeal than the salmon.