Originally Posted by
jlin
don't quote me on this, but you're probably running at 68x107. at least that's how pistas in the past have been. if in doubt, bring it to any LBS and they can usually run a measurement for you free of charge, and if you're nice.
bulletproofs are doubles, and with a 107mm bb, will run a 47.1 chain line on the outside, 39.7 on the inside. neither of these are a really good chain line for standard track spacing, which usually leaves the rear at 42, though i don't think being off by 2mm (from the inner) will be a big deal if you have a tight chain. in general though--and this is just my preference--i'd stay away from bulletproofs for its q-factor, though many people have run bulletproofs just fine.
cool, thanks! I have until spring for this project (my bike is tucked away in storage for winter), so I am just starting to look at options, maybe I will hold off and go for a true track crank.. and actually pull my bike out an measure before I do anything.