BB drop is a framebuilders' term. When they desgn the frame on paper (or computer!) they have no way of knowing what profile of tires will be used with this bike so they can't set a BB height. So thet set a BB drop from a place they know - l line between both axle centers and it's measured to the center axis of the BB shell.bikerboy said:Is it measured from the center of the BB or from the bottom of the shell? While perusing geometry charts, I have also come across the measurement BB Drop. Is that the distance between the center of the BB to the bottom of the shell? Thanks.
Here's a site with a whole load of framebuilding and spec info -Fixintogo said:Follow-up question:
Are there standard BB drop measurements to which framebuilders generally adhere?
In other words, what is the "normal" range of BB drop for various bike types: mountain, 29er, road, cyclocross, and track? Anyone?