I posted this a little earlier on the SS/FG forum, but I figured you guys would have more experience with Biopace, so:

Yesterday I went and picked up this Nishiki Modulus off of craigslist for my girlfriend's birthday; its got Biopace chainrings on it.





I'm going to be converting this bike to singlespeed, and I was curious to see if anyone had any experience with these chainrings. I checked Sheldon's website, and he says they work fine with a fixed gear. The thing is, on a fixed gear, the chainring will be constantly rotating, so the chain will never be at it's loosest point in the rotation for more than a split second. Because this bike will be coasting on some relatively crappy roads, I was wondering; if the bike coasts when the chain is the least tense in the rotation and hits a bump, will the chain be loose enough to come off the chainring? Is the change in tension that Biopace creates going to be a problem at all? I just want to make sure that this bike is mechanically sound before it hits the street.