With modern, 2-piece cranksets with 1 arm attached to the spindle, the spindle length is a given for the crank model, and crank models generally work only within rather strict limits, that is, for certain types of frames and rear hubs. For the older type of 3 piece square taper cranksets, with arms both separate from the spindle, mfs recommend a spindle length for a given rear hub width, sometimes modified by the width of the chainstays where the are crossed by the rotating arms. But if you want to mix and match, say, to use an old Deore triple on a 5 speed or, at the other extreme, a 10 speed rear road bike, you'll need to experiment or ask someone who has combined the 2 and knows the chainline wrt to the width of the rear hub.
The situation can also be complicated by how you want to center your chain, and whether you value chainline over minimum Q. I've used a 108 mm spindle and a 145 mm spindle on almost identical frames, the choice determined by chainline option, Q or "tread" or width between the outside faces of the crank arms at pedal interfaces, gearing choices, rear hub width, and of course the crank arm flare. Patrick "learned the hard way that flared crank designs used different spindle lengths than straight ones" Moore On Sat, Apr 30, 2016 at 3:58 PM, René Sterental <orthie...@gmail.com> wrote: > Slightly off topic... How do you determine the proper width of the bottom > bracket? > - when getting a custom frame and a set of cranks you've never had before? > - when switching to a new different crankset than what you had before? > > René > > -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bunch+unsubscr...@googlegroups.com. To post to this group, send email to rbw-owners-bunch@googlegroups.com. Visit this group at https://groups.google.com/group/rbw-owners-bunch. For more options, visit https://groups.google.com/d/optout.
