Bit hard to describe this but bear with me.
Last year I had a fairly big crash on my bike, which is a Specialized Camber. I can't recall the crash but nearing the end of my recovery when I was cleaning the bike I noticed I had bent the RH crank arm. http://singletrackworld.com/forum/topic/does-this-look-bent-to-you-1 I suspect what happened was my RH pedal caught a rock/root and threw me off, as I was on the CwmCarn red run so travelling a fair old pace and stopped pretty quickly.
Now, rather ashamedly, I went out for my first ride since the crash last weekend. All felt fine except for riding on some road sections between the trails. Whilst sat on the bike freewheeling it felt like the back of the bike was rocking (or swaying) from side to side, almost as if riding with a buckled wheel.
This was only very slight and I couldn't notice off road, just on road. The wheel doesn't seem to be buckled either (not significantly and I don't have a jig) so any ideas what else it could be? I had a worrying thought I might have damaged the frame/knocked it out of alignment but this seems unlikely. Its got to be the wheel hasn't it?