Bicycle Mechanics - Square Taper BB's - Mtn Triple to Road Triple

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lordconqueror
03-29-07, 09:58 AM
I have a bike that uses a square taper bottom bracket, currently with a mountain 26-36-46 crank on it. is it safe to assume that a road triple will use the same width BB axle?

maddmaxx
03-29-07, 10:30 AM
I suspect that the road triple may want 5mm more bottom bracket length as it was originally optimized for a 130mm rear spacing chain line. This assumes that you are working on a modern MTB with 135mm rear spacing.
lordconqueror
03-29-07, 10:50 AM
Actually, it's a Redline road bike with 130mm rear spacing. I'm not worried about having a screwed up chainline as long as it gets me from work and back.

Am I to assume that this would probably work? I tried putting a double on the BB, but the small ring, a 42, came really close to rubbing against the frame, so i didn't even bother trying to actually ride it. It seems reasonable that the small ring on a triple would probably allow for more space between the chainrings and the chainstay.

Portis
03-29-07, 10:51 AM
I have a bike that uses a square taper bottom bracket, currently with a mountain 26-36-46 crank on it. is it safe to assume that a road triple will use the same width BB axle?

No. The crankset manufacturer sets the spec for the bb spindle length.
lordconqueror
03-29-07, 11:06 AM
alright, gotcha.
tellyho
03-29-07, 12:46 PM
Check out Sheldon's page for cranksets and associated BB spindle lengths.