Is Mega Exo BB same as GXP?

Weeman1973

I have a Kuota frame set with s BB386 & looking to change chainset.

I'm looking at an FSA SLK which comes with Mega Exo BB.

I know I can buy adapter cups to allow my BB to accept GXP style cranks but it doesn't say anything about Mega Exo?

I believe the issue might be in spindle length as they need to be 86mm to fit the BB386 but I'm thinking if Mega Exo & GXP are the same, surely the adapter cups to change my BB386 to GXP will work for Mega Exo too?

super_davo

No, Gxp has a stepped spindle, so one side is 24mm but the other is 22. Megaexo is the same as Hollowtech 2 so you should be able to find an adaptor.
Really good article here:
http://www.bikeradar.com/gear/article/c ... ets-36660/

Weeman1973

super_davo wrote:

No, Gxp has a stepped spindle, so one side is 24mm but the other is 22. Megaexo is the same as Hollowtech 2 so you should be able to find an adaptor.
Really good article here:
http://www.bikeradar.com/gear/article/c ... ets-36660/

Thanks for that. I already use a Dura Ace chainset so have adapters in place for that. You think those adapters I use for the Hollowtech II DA cranks will also be suitable for the FSA cranks with Mega Exo BB?

lesfirth

FSA cranks with a 24mm spindle will fit hollowtec 2 bottom brackets but in my experience they are a tighter fit and they do not slide together as Shimano cranks do. They will need a good clout with a rubber hammer to assemble them.

MisterMuncher

Depends on your adapters, really.

If it's an adapter that lets you thread in a regular BSA bb, then you can fit a MegaExo BB. If it's an adapter based on bushings/spacers that fit into 30mm ID bearings then it won't work.

There's actually three road MegaExo variants about. The mid-range (Gossamer, Energy) is 24mm id, and the same as Shimano. The low end (Omega) is 19mm and compatible with nothing. As far as I remember, the top end (Energy 130mm BCD, SlK and K Force are different again, though I'm buggered if I remember how.

Weeman1973

Wow - they really make it easy don't they!

Looks like the easiest thing will be to either buy a BB386 specific Chainset (mega bucks, even for the cheapo FSA Gossamer style!) or get another Hollowtech II chainset that I know works with the adapters I am currently using.

MisterMuncher

Sorry, to clarify. If your adapter is a spacer/sleeve design that the crank slots straight into, then you'll be able to fit the FSA crank in the same way. The high end FSA cranks don't use pinch bolts a la Shimano, but a wave washer and a single axial crank bolt. This is the reason for the other variant of megaexo BB. It'll work, but I think the different fitting for the NDS crank can cause issues down the line.

Weeman1973

MisterMuncher wrote:

Sorry, to clarify. If your adapter is a spacer/sleeve design that the crank slots straight into, then you'll be able to fit the FSA crank in the same way. The high end FSA cranks don't use pinch bolts a la Shimano, but a wave washer and a single axial crank bolt. This is the reason for the other variant of megaexo BB. It'll work, but I think the different fitting for the NDS crank can cause issues down the line.

Yep, its he bush / sleeve style adapters I use to convert my BB386 bearings (30mm) into Hollowtech II compatible 924mm) rather than screw types.

Also looking at a high-end FSA crank like SLK or K Lights o these will come with the washer / crank bolt you mention so I think it's regular Hollowtech II cranks just because I know they work with my set up.

Difficulty is finding a 50/34 chainset with 170 cranks in a high end (Dura Ace) Hollowtech II to fit 10 speed which is why I was looking at the FSA in the first place.