BB question

[Deleted User]

Hey - noob with limited bike tech background (enough to hurt my wallet), doing some research before I pimp my ride.

Q: I have a Specialized Transition. Current BB is the OSBB (Specialized specific, but apparently similar to BB30 standard). Am I limited to only OSBB/certain BB30-based cranks, or would my (ok, here I'm going non-technical) "crosstube on the bottom of the bike into which the BB and crank go" accept other Bottom Brackets? 

I have a 130diam 52/39 Specialized/FSA Krono crankset that I want/need to swap to compact 50/34. I would do it with rings, but compact rings are 110mm, so that won't work. 

The reason I ask is that I am considering swapping out the SRAM for Ultegra (or DuraAce) Di2. I don't know offhand what BB the shimano takes (MegaExo? probably depends on the crank), but if I'm locked into the BB30/OSBB spec then the question is moot, and I'll just upgrade to new-spec Red.

(NOTE: component weight is irrelevant. I carry enough extra pounds on me that a few grams will not make any difference.) 

 

 

novaavant

You can get adapters that will allow you to use different crank sets including Shimano and SRAM GXP in a OSBB frameset. The versions of adapters available are either machined aluminum from Enduro or Delrin which is made by Wheels Manufacturing.



http://www.enduroforkseals.com/id255.html



http://wheelsmfg.com/products/bottom-brackets-front-drivetrain.html



You can get both here with 25% discount currently for Black Friday. http://www.artscyclery.com/

[Deleted User]

 I'll be damned! Adapters. I've been searching and searching and never turned up that solution. Guess my google-foo isn't strong enough. 

Thanks!!!!

Any sense of whether they are less durable or prone to failure, compared to a straight  (ie no adapter) bb setup?

novaavant

Straight BB30 in the OSBB is always better but the adapters work pretty well. I have a GXP Quarq so this is the route I will take when I upgrade to my planned next frame because I move them between bikes. If I didn't own a crank set though I would go native versus adapters.

Read on here: http://blog.artscyclery.com/ask-a-mechanic/ask-a-mechanic-adapting-sram-gxp-to-pf30-bb30-bbright/

Dino Sarti

As Attila points out, just about anything is possible. The issue is that in recent years, as I have been told, the number is BB "standards" has exploded. There are now sooo many standards that there frankly is no standard. As a result, there is a conversion, adapter or kit out there for just about anything. My Madone has BB90. To get the Quarq to fit, had to buy a SRAM bearing kit from trek to make it work, but it works like a charm.

[Deleted User]

 "Standard" with regard to BBs seems like a cruel joke!

Dino Sarti

True. The bottom bracket is an enigma rapped in a riddle...