Oops! Sorry Emily- I missed the part about single speed.

Quote Originally Posted by spokewench View Post
I would also think that the way a FS bike works with pivots and movement in the rear might even make a single speed impossible since there is no deraileur and no give in the chain area, so I would think that the chain would just bounce right off all the time. There are ways to use a tensioner on a regular hard tail conversion to single speed to keep this from happening, but I'm not quite sure how that would work with a FS bike???

You could get a cheap suspension seat post to get a little cush for your seat. Maybe, a suspension fork for your front?
I think Spokewench is onto something here. I don't see how the rear triangle could move and still maintain the chain tension, unless the rear wheel moved in a fixed arc around the bottom bracket. That said, I sort of recall a discussion about single speed FS bikes over at the MTBR forums. It might be worth a check over there...