Bottom brackets, Road/Mountain
 

I have a Sugino triple I want to use for a build. I see Sugino suggests 110 BB vs 113 BB for road vs mountain. Why the difference on the two? Inner chainring clearance?

130mm vs 135mm drop out spacing?
Split the diff.

Aha! Got it. Thanks

Don't be too obsessive about CL.
It presumes you use all cogs & rings an equal amount and gives the best "average" CL.
That may work for robots.

I tend to use the middle ring & outer cogs the most.
I use the next longer BB to give me a best average CL for the gears I use the most.

If you're already biased to the right chainrings, why would you move it further right with a longer spindle?

Off-road frames often have curved chainstays to accommodate wider tires, and need the crank arms positioned further out to clear the stays.

Yabut…

It depends on the crank design. While mountain bike frames are wider, some mountain bike cranks use narrower spindles than road bike because the arms curve inward towards the frame more than road cranks do. For the Sugino cranks in question, the recommendations are correct but they might not be for other cranks.

Why would the designated spindle for any crank be assumed to work on a completely different model?

:foo::wtf::popcorn:D

care to present an example of these mysterious reverse curving MTB cranks, Cyco? the ones i've seen/installed/stock all "curve" outward, then go parallel to the main frame line before reaching the pedal threads.... not one "curves" in.. not one. except a badly bent 105 crankset that already went to the scrap heap.... someone parked a Buick on top of that bike...

Because there is no such thing as a “designated spindle” when it comes to internal bearing bottom brackets.

What doea that have to do with the topic?

You're only futhering the point that cranks and BBs are a system, not a mix and match.