Cottered axle lengths

OldFrank

Retro Guru
Do cranks sit in a different place on a cottered axle? I'm replacing the Bottom bracket and cranksets on a tandem, but the axle lengths axles about 135 and 138 mm. Do i need the same length for a square taper?
 
I would say not if you take a cottered axle end to end it includes the cranks with a square taper the axle is set back in the cranks. do some maths and work out how much axle is set back from the face of the cranks times that by 2 and subtract that from the cottered axle length and this will give you a rough guide to the size of square taper BB you need to maintain close to the original chainline.
 
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