I know this has been discussed here before, but I'm at work and don't have time to search at the moment, so I'm going to very quickly start a new thread...

The stock canti brakes that came on my 2006 Specialized Tri-Cross squealed terribly on my first singletrack ride a month or so ago, and continued squealing afterwards. I cleaned my rims with rubbing alchohol, scuffed up the brake pads with sandpaper, and attempted to adjust them so they'd be toe'd in. Didn't help.

So, I had a pair of Kool Stop's installed. They squealed on the first ride. I went back and had them adjusted. They were fine at the beginning of the next ride, but were squealing again by the end. On the singeltrack ride I did yesterday, they were horrendous. The front brake was fine, but I was hesitant to use the rear brake because it was so loud. Made for a less-than-secure feeling even on an easy trail.

I'm going to take the bike back to the shop, but I'm curious what you ladies think the problem might be. My suspicion is that it's either one of the brake arms (I noticed a teeny bit of play in one of the rear brake arms yesterday when I was again attempting to toe in the new pads), or the rims. Any ideas or recommendations before I hit the LBS?