Bottom Bracket Headache

Hi guy's,

I'm after advice regarding bottom bracket fitments. :facepalm:

I have a Specialized Rockhopper with a 68mm english BB Shell, currently with a square taper BB.
I've upgraded the rest of the bike to XTR 9 speed and the chainset is next on the list.
I really like the idea of changing from 3x9 to 2x9.

Every chainset I seem to see available with 2 rings seems to be a BB30 - like SRAM GXP for example.

Am I right in saying a BB30 BB is to large for the frame?
From what else I have read it seems Hollowtech might be to large also??

I looked at ISIS but these don't have the best rep. So what other options are out there that will fit into the shell? Or will I be limited to square taper chainsets?

Any help greatly appreciated!!!

Shimano hollowtech will fit that shell, just don't over tension the cap bolt when you fit the left hand crank & do the left hand clamp bolts up to the correct torque settings.

Thanks Dickyboy,

That's great. I guess that covers the hollowtech II as well?
Maybe an XT 2x10 chainset would be an option?

I have a SRAM XX carbon 2x10 available, but it's a BB30. Might have to advertise it on here to purchase a hollowtech...

Cookielad":2qm6j2pa said:

From what else I have read it seems Hollowtech might be to large also??

Click to expand...

Dunno where you read that, but i'd not take anything from that site/source at face value ever again.

Hollowtech/octalink is a direct fit to 68/73 shells. Many versions don't even need spacers.

HollowtechII is almost a direct fit. But it requires spacers (as the axle length is fixed) so one driveside spacer on 73 and three on 68 (two drive side, one idle).

FWIW, i have the XT (M785) double on two 73 shelled bikes, light, stiff and durable. One of them is even running with XTR 9 speed....... another (6 bike is running the old SLX double/bash, and XTR 9 speed

Oh, as dickyboy points out, if you go hollowtechII, do not overtighten the LH preload cap, you'll kill your bearings in weeks, also worth making sure your cups are parallel (either by facing the shell, or just cleaning the ends of the shell up.) cups that don't line up will not do your bearings any favours either.

Cheers Mattr,
Yep, definitely won't be going to that site again.
I think hollowtech II will be the way forward.

Was hoping thie Sram XX carbon one I already have would fit. I've seen a guy who has used a Zipp Vuma External BB30 shell and fitted a X1 single crank on an English BB she'll, but don't want to go down an expensive route with BB's etc and have a ton of used parts that don't fit as I think the spindle will be to short lining it up against a square taper BB I have knocking around.

How have you found the gearing with a 2x9??

Gearings fine, just end up closer to cross chaining a bit more often.
Not enough to actually matter though!