Originally Posted by
himespau
but isn't it an oval so that when the chain is wrapped around both "points" of the oval (the long ends are up and down) there's more contact than when only one long end is wrapped (when they're horizontal)? maybe I'm just thinking about it all wrong.
you are right.. it's just biopace rings are not really "oval".. they very close to round and the difference isn't enough to make the tension an issue.. the chain will not come off if you set the tension properly. I know cause i've made a fixed gear with the same biopace rings that guy is using (well not those exact ones, but the same model)