Originally Posted by amahana1
I have seen this in a number of threads. I have done a search trying to find what is it exactly with no luck. Also, I have seen BCD used, what is BCD?
BCD = Bolt Circle Diameter. This is the distance from bolt hole to bolt hole on a Chain Ring.
Q Factor as per Sheldon Brown:
Q-factor
In Fit-Kit © terminology, this is a factor based on the relative length of the femur compared to the rest of the leg. A large Q-factor is interpreted as an indication that the rider in question needs a frame with a shallower seat tube angle.
Also, another name for the tread of a crank set.