Originally Posted by
PromptCritical
I have a question about determining the needed width of a bottom bracket spindle.
I'm building a gravel bike with a Lynskey frame, 1X crank and SRAM XDR hub.
I presume, the chainwheel should be roughly parallel to the middle of the cassette, which is easy to measure (frame center to chainwheel).
Is that the correct measurement, and do I just double that number to come up with the proper width spindle?
With more modern cranks that use an external bottombracket, the spindle is usually fixed to the crankarm and determines designed chainline. A little adjustment is possible with spacers on the BB but very limited.
Wtih cranks that uses an older type of BB (square taper, Octalink...), there is usually a recommended spindle length and the resulting chainline. There are differences in how the crank is offset on the spindle, so you need to find the 'normal' spindle & chainline, then make adjustments from there on the spindle length. Additionally, not all BB are symmetrical, so a 6mm longer spindle may not be 3mm on each end.
So specifics are needed to assist you here. Let us know what cranks you are considering.