That's one of the things that I look at initially and it's not rubbing, I didn't check the brake caliper to see if it was misaligned. I was told by a bike buddy that it possible that it's possible that there is some internal friction happening that's creating heat and perhaps creating some binding. But there is no real way to know. I didn't notice this issue last season and I've only had these wheels for two seasons AND it spend the entire 2006/2007 winter on the trainer. It's a Xero Wheelset. Prior to this set I had a great pair of Spinergy Spox.... should have kept them.