# Bottom Bracket Compatibility: Shimano 105 and FSA MegaExo



## ScaryBikes (Oct 23, 2009)

Hi fellow riders, I need some help confirming something:

Would a Shimano 105 BB (for R600 compact cranks) work with an FSA MegaExo-specific crankset? As in, if I already have the 105 BB installed, can I change the R600 cranks and replace with another pair of FSA MegaExo cranks?

Thanks for your help in advance!

Ride On,

E.


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## danl1 (Jul 23, 2005)

In some combinations, it's nominally possible. Problem is, not even all of the Mega-Exo BB's are cross-compatible, so it'd very much matter which (and unfortunately, I don't have exact info on all of the details.)

IIRC, the nominal difference between the two standards is 1mm in bearing width, but that is accounted for by differences in seal, cap, washer and spacers. I don't correctly remember which is wider or narrower, but because certain FSA cranks are famously tempermental about width to ensure a good lockup without overloading the bearings, I'd proceed with caution.


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## MisterMike (Aug 12, 2004)

danl1 said:


> In some combinations, it's nominally possible. Problem is, not even all of the Mega-Exo BB's are cross-compatible, so it'd very much matter which (and unfortunately, I don't have exact info on all of the details.)
> 
> IIRC, the nominal difference between the two standards is 1mm in bearing width, but that is accounted for by differences in seal, cap, washer and spacers. I don't correctly remember which is wider or narrower, but because certain FSA cranks are famously tempermental about width to ensure a good lockup without overloading the bearings, I'd proceed with caution.


Sounds like what my research has told me as well. For example everything I've seen seems to point to me being able to use a Gossamer Mega-Exo with a 105 or Ultegra Hollowtech II BB. But, other FSA cranks aren't compatible. 

Check out http://velonews.com/article/86337 Scroll down to the part titled "Bearing bad news". There is some Q/A but the interesting part to me is FSA's response which implies Chris King and Shimano BBs are equivalent dimensions.


> The short answer; no, the *FSA K-Force Light Rd. Crank is not compatible with a Chris King bottom bracket (made to Shimano compatible dimensions)*. Also, the K-Force Rd. crankset will not be compatible either.
> 
> The FSA BB8200 (meant for K-Force Light) uses a 6 mm width bearing. This allows us to make the bottom bracket outside to outside dimension more narrow providing room for a wave washer. The BB8000 (meant for K-Force) does indeed use a 7 mm width bearing, yet its design does not allow for use of a Chris King bottom bracket.
> 
> ...


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## tihsepa (Nov 27, 2008)

Yes. The Gossamer is compatible with a Shimano BB. I have replaced that Mega-Expo bracket with a Shimano a few times.


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## danl1 (Jul 23, 2005)

MisterMike said:


> Check out http://velonews.com/article/86337 Scroll down to the part titled "Bearing bad news". There is some Q/A but the interesting part to me is FSA's response which implies Chris King and Shimano BBs are equivalent dimensions.


An interesting add to that: I ordered a replacement for a Gossamer set, and received a part labeled "BB6000/8000" (etched into the cups.)


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## Rodder07 (Nov 18, 2008)

*Mega EXO to HollowTech II*

Could I add.... HollowTech II has a larger spindle, so we need to change the bearing set... what bearing set can to into the EXO BB cups, and fit the HollowTech Integrated Crankset?

I thought the mega EXO was compatible, so didn't anticipate needing larger ID bearing set. Any advice appreciated....


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