Canon 20D, but the camera's the least important part of the equation. The off-camera flash helped a lot (courtesy of somnambulant) and I use a good lens (one of the "L" series Canon ones). I like my "night racing" shots to be a bit ****zy, but if you want sharp photos (like the one I took for the Cycle Solutions team of one of their riders) a decent flash is pretty much the only way to go.

PS. Wes/Keith/V.Y. ... there's a big-ass version of that photo of one of your riders on my Flickr page if he/the team ever wants it for anything.

PPS. This is the photo I always have in mind when I shoot night races. It's one of my favourites and I shamelessly (try to) emulate whenever the situation presents itself.