Might be the tire as much as the rim. I've got a set of Challenge Paris-Roubaix tires that ride delightfully, but I've decided that I will never use them again. It's not worth the blisters on my thumbs and the fact that I ruin at least one inner tube every time I take them on or off. Plus I don't think the rubber is as sticky as my GP4000S IIs. If I want super-fast clinchers, I'll get the Specialized Turbo Cottons, maybe.