My wife has a older Trek 800 that she uses for a path bike. The brakes are canti's. Both the front and back now squeal so loud when she hits her brakes it hurts our ears. I have tried to adjust them, clean the rims with rubbing alcohol, I don't know what else to do. From what i can see the pads have tons of life left in them, but maby I am wrong. Any other suggestions, before I take it to a shop?