Cycling UK Forum

a little hard to describe but is there a standard orientation in which the holes in cranks are cut for square tapered BBs?

a friend bought a left hand crank in the hope of matching it to an existing chainset.

the hole in the left crank was cut with the 'square' rotated 45 degrees to the chainset's own 'hole' hence giving the effect that the cranks on either side weren't parallel when fitted.

did he cop for a dodgy crank? or do manufacturers merely line up the holes in their own sets? does this by any chance differ for tandems?

(apologies if you are now confused!)

Typically the corner of the BB square points in line with the crank arm - Campag, Shimano, Sugino, Middleburn are all like this, at least for things made in the past 15 years. There are a few (as you have discovered) which don't.

why oh why oh why!!!

next you'll be telling me that manufacturers make cassette sprockets slightly different widths apart and stuff like that......

the two configurations are often known as 'diamond' (the most common) and 'square-on' types. Quite a lot of the inexpensive suntour cranksets fitted to MTBs are square-on types, and there are a few others.

Yet another trap for the unwary...you just need to check to be sure....

cheers

annoyingly it was a rear tandem left hand crank in 172.5....i can't remember the brand....but it wasn't a cheapo!

Don't forget there are two different "standards" of taper as well