# Are Shimano external BBs compatible with FSA Mega EXO cranks?



## dunklegelb

Greetings!
Will Shimano Dura Ace, Ultegra or 105 external BBs work with the FSA Gossamer cranks?
Lookin to replace the MegaExo BB the cranks came with.


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## danl1

dunklegelb said:


> Greetings!
> Will Shimano Dura Ace, Ultegra or 105 external BBs work with the FSA Gossamer cranks?
> Lookin to replace the MegaExo BB the cranks came with.


Yep. Slight difference in the 'top hat' outer seals is the only spec difference. 

Just curious, why are you looking to replace the Mega Exo's ? They're not inherently better or worse than the Shimano equivalent. If they're toasted, it may be as much a result of setup / adjustment problems as the quality of the item itself. Just saying, if you feel they've died an early death, it's worth checking on underlying causes. If you aren't careful, a mix-and-match might make the problem worse rather than better - depending of course on what's going on.

Another possiblilty might be to look at Boca or Enduro and only replace the bearings.


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## backinthesaddle

Short answer w/o all of the wordy wordness...

YES, FSA cranks work just fine with Shimano BBs and vice versa. 

I'm running FSA SLK carbon cranks on my cross bike with a Dura-Ace BB and it's perfect. No fit issues, no noise, smooth as a baby's bottom.

That being said, Shimano BBs do, in fact, tend to last longer than FSA. YMMV...:thumbsup:


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## Dr_John

> That being said, Shimano BBs do, in fact, tend to last longer than FSA


I'll second that, having put a lot of miles on both types.


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## function

I'll 3rd that after going through a number of FSA BBs. The difference is 7000-8000km (FSA) vs 20,000km+ (Shimano 105, still going).


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## david462

with all those yes's, I'm gonna have to go ahead and say last I checked, Shimano bb inner diameter is slightly larger than FSA's.


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## dunklegelb

Thanks for the replies, I'll prolly end up goin to my LBS and checkin with them as well.

Well I got the Gossamers used (theyre in great shape!). The guy I got them from 
included the MEGAEXO BB. He said he got the cranks and BB as extras when He bought a new bike, they were already previously used. 
Since I dont know how many miles had been put on the BB I thought Id just get a new one. 

So I can replace just the bearings?? (This is my first experience with a External bearing BB)


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## backinthesaddle

david462 said:


> with all those yes's, I'm gonna have to go ahead and say last I checked, Shimano bb inner diameter is slightly larger than FSA's.



You don't read well, do you? THEY ARE INTERCHANGEABLE, PERIOD!!!!!!!!!!!!!!!!!!!!!!!!!!!


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## danl1

If you want to and know how to work with press fit bearings. That's not to say it's hard, but it can be screwed up.

See Boca bearings for one source of aftermarket bearings. They can also be had from industrial supply houses if you know what you are looking for. There are also more cycling-centric sites that offer confidence in sizes for a bit lower value.

To those insisting that all Shimano are vastly better than any FSA... I won't argue the point as such, as Shimano is obviously first-rate stuff. However, I'd be interested to hear the experiences of those that have used both with the same crankset. Point being, FSA's crank adjustment mechanisms (particularly on the SLK series) are fairly well designed to eat bearings. Comparing Shimano BB's in Shimano cranks as compared to FSA in FSA isn't exactly fair, odd as that sounds to say.


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## backinthesaddle

danl1 said:


> If you want to and know how to work with press fit bearings. That's not to say it's hard, but it can be screwed up.
> 
> See Boca bearings for one source of aftermarket bearings. They can also be had from industrial supply houses if you know what you are looking for. There are also more cycling-centric sites that offer confidence in sizes for a bit lower value.
> 
> To those insisting that all Shimano are vastly better than any FSA... I won't argue the point as such, as Shimano is obviously first-rate stuff. However, I'd be interested to hear the experiences of those that have used both with the same crankset. Point being, FSA's crank adjustment mechanisms (particularly on the SLK series) are fairly well designed to eat bearings. Comparing Shimano BB's in Shimano cranks as compared to FSA in FSA isn't exactly fair, odd as that sounds to say.


I did use both with the same SL-K crankset. The FSA went to sh*t in 3 months. The D/A is going on 10. I have the crank/BB setup on my Salsa Las Cruces cross bike that's used for everything from rainy road rides, trips to the store, singletrack and racing. The D/A is just better.


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## david462

backinthesaddle said:


> You don't read well, do you? THEY ARE INTERCHANGEABLE, PERIOD!!!!!!!!!!!!!!!!!!!!!!!!!!!


no I read quite well, actually. Do you believe everything you read on the internet, especially forums? I was just saying, going off of what I can remember, when trying to fit a Shimano Ultegra bb with and FSA crankset, the inner diameter of the bearing was slightly too large around the FSA spindle. Maybe I'm remembering wrong and it was a different combo though. I believe I didn't say anything about being right, just was what I thought I remembered. Get it?


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## function

I used FSA BBs with Gossamer crankset and 105 BB with Gossamer crankset. The 105 BBs outlive the FSAs by a considerable factor.


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## backinthesaddle

david462 said:


> no I read quite well, actually. Do you believe everything you read on the internet, especially forums? I was just saying, going off of what I can remember, when trying to fit a Shimano Ultegra bb with and FSA crankset, the inner diameter of the bearing was slightly too large around the FSA spindle. Maybe I'm remembering wrong and it was a different combo though. I believe I didn't say anything about being right, just was what I thought I remembered. Get it?


No, you don't read you dope! In my FIRST post of this thread, I said that I was using a Shimano BB and a FSA SL-K crank and it worked perfectly. 

I don't have to believe what I read on the internet as I have ACTUAL EXPERIENCE AND KNOWLEDGE OF THE SUBJECT!!!!!!!!!!!!!!!!!!!!!!!!!!!!
:mad2: :mad2: :mad2: :mad2: :mad2: :mad2: :mad2: :mad2: :mad2: :mad2: :mad2: :mad2: 
You are wrong, PERIOD!

Reading is fundamental...


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## david462

backinthesaddle said:


> No, you don't read you dope! In my FIRST post of this thread, I said that I was using a Shimano BB and a FSA SL-K crank and it worked perfectly.
> 
> I don't have to believe what I read on the internet as I have ACTUAL EXPERIENCE AND KNOWLEDGE OF THE SUBJECT!!!!!!!!!!!!!!!!!!!!!!!!!!!!
> :mad2: :mad2: :mad2: :mad2: :mad2: :mad2: :mad2: :mad2: :mad2: :mad2: :mad2: :mad2:
> You are wrong, PERIOD!
> 
> Reading is fundamental...


Whats wrong with you. I dont care if you say have "actual" experience. On my end, that still means I read something on the internet posted by some other dope, and I am not going to automatically believe or not believe right away.


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## stevesbike

FSA states that their bottom brackets are not even compatible among their different cranks (http://www.bikeman.com/images/stories/RepairTechInfo/externalbbfitchart.pdf), so I'd guess you'd at least void a crank warranty by using a Shimano BB with an FSA crank regardless of whether it can be done in practice. There could also be differences in terms of preload and torque involved on the crank. That's certainly a major difference between SRAM and Shimano cranks.


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## framed

*Not so good the other way around?*

http://www.competitivecyclist.com/r...rket-dura-ace-10-speed-bb-unit-3994.19.1.html:

"Most people who purchase the FSA ceramic BB's from us are in fact using them on Dura Ace 10-speed cranksets. The inner sleeves of an FSA BB were designed around FSA cranksets (which has subtle-but-meaningful design differences from Shimano), so it required the tedious trial and error of removing and re-installing seals and sleeves in order to minimize the drag between the FSA BB and the Dura Ace crank."

http://www.superflycycles.com/servlet/-strse-275/Enduro-Hybrid-Ceramic-Bearing/Detail:

"We have two different styles. One is the Shimano version which will fit Shimano, Truvativ and everything else besides FSA and the FSA version. The difference is that the FSA version has an inner bore slightly bigger than 24 mm (it is around 24.03 mm). This is because FSA crank spindles are not exactly 24.00 mm and this will take care of the everly tight issues with using the standard MR2437 with FSA cranks."


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## Richard

All I know is I've never been able to get a bit of side play out of my FSA SLK's since new. And that was with the help of our 40+ years of experience Service Manager.

When it takes a dump (which I figure it will sooner or later) I'm putting in a Campy UT.


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## danl1

function said:


> I used FSA BBs with Gossamer crankset and 105 BB with Gossamer crankset. The 105 BBs outlive the FSAs by a considerable factor.


Curious - how does your Gossamer left-side connect? I've seen them with both the Shimano-style pinch bolts and the slk style 'screw-in'. 

It's interesting to see the anecdotes from both. I have a Gossamer that at 7k/miles is still smooth, solid, and running clean. The Ultegra cups I originally ran it in were still OK at that point, too, but not quite in as good shape. Lots of possiblities (maintenance, usage, adjustment, etc) could account for the differences.


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## kbiker3111

david462 said:


> Whats wrong with you. I dont care if you say have "actual" experience. On my end, that still means I read something on the internet posted by some other dope, and I am not going to automatically believe or not believe right away.


I think there was some not so obvious sarcasm being used...


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## danl1

It appears Superfly has taken that down - at least I can't make the link go. Just as well, because it's wrong information. FSA and Shimano are compatible, though (as mentioned) there are differences in the 'top hat' outer seals. However, Truvativ/SRAM are not compatible with Shimano - on them, the left and right side bearings have different inner diameters. 

http://www.velonews.com/article/75879

The 'standard', such as it is, is based on a 24mm diameter shaft. Shimano and some FSA use 25mm inner diameter bearings, with a shim or 'top hat' outer seal that takes up the difference. Others use 24mm inners for a direct press fit to the shaft. There are also some generational variances in Shimano regarding whether the bearing is 6 or 7 mm thick, and a change in shim to suit.

GXP (SRAM / Truvativ) uses a 25mm inner on the right side, and a 24 on the left, with a direct fit to the shaft.


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## framed

danl1 said:


> It appears Superfly has taken that down - at least I can't make the link go


The problem was that I had put a colon ":" and the end of the link that was causing a problem - sorry about that.


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## danl1

backinthesaddle said:


> I did use both with the same SL-K crankset. The FSA went to sh*t in 3 months. The D/A is going on 10. I have the crank/BB setup on my Salsa Las Cruces cross bike that's used for everything from rainy road rides, trips to the store, singletrack and racing. The D/A is just better.


I'd agree that D/A is probably better, but I wonder if that's the whole story. Depending on the exact model year and setup, SL-K's put way too much sideload on the bearings. I understand they've fixed it, but don't know for sure. Meanwhile, the thinner Shimano bearings wouldn't have been overloaded. They may show some sideplay, but that could also be covered by close fits and the choice of spacers/shims/seals used.

I wonder if there's any experience using FSA bb's on Shimano cranks, and the relative performance there?


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## function

danl1 said:


> Curious - how does your Gossamer left-side connect? I've seen them with both the Shimano-style pinch bolts and the slk style 'screw-in'.
> 
> It's interesting to see the anecdotes from both. I have a Gossamer that at 7k/miles is still smooth, solid, and running clean. The Ultegra cups I originally ran it in were still OK at that point, too, but not quite in as good shape. Lots of possiblities (maintenance, usage, adjustment, etc) could account for the differences.


Pinch bolts on my gosammer, since i maintain my bikes there hasn't been a change in procedure between the two.


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## backinthesaddle

david462 said:


> Whats wrong with you. I dont care if you say have "actual" experience. On my end, that still means I read something on the internet posted by some other dope, and I am not going to automatically believe or not believe right away.


Did you know that Santa Claus isn't real? Nor the Easter Bunny? 

Oh, and the Government DID kill Kenneday...SSSHHHHH, don't tell anyone...

I can provide pictures if you like...of the crank/BB setup that is...

The other stuff is double Top Secret...


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## youngjun91

backinthesaddle said:


> Did you know that Santa Claus isn't real? Nor the Easter Bunny?
> 
> Oh, and the Government DID kill Kenneday...SSSHHHHH, don't tell anyone...
> 
> I can provide pictures if you like...of the crank/BB setup that is...
> 
> The other stuff is double Top Secret...


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## youngjun91

The spindle diameter of Shimano is 24.0 mm. The spindle diameter of FSA can be 24.00 to 24.07mm. I've read many people having to "persuade" the spindle of FSA into the bottom bracket bearing with a mallet and grease. I chose to lightly sand the inner diameter of my Shimano bearing since I was pressing too hard and it didn't feel good forcing the spindle through the bearing. Then it went it very nicely. There are mechanical tolerances involved so your miles may vary a little bit, by a few hundredths of a millimeter. Shimano spindles are generally a few hundredths of a mm smaller than FSA MegaExo. Read the note at the bottom here: Wheels Mfg BB30A Outboard Angular Contact BB for 24 mm cranks (Shimano) - Black "_Note: FSA MegaExo spindles can be between 24.00mm and 24.07mm in diameter. If your FSA spindle is 24.07mm, this BB will not work! Please purchase our FSA 24.07x37 ceramic hybrid bearings separately."_


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## Kerry Irons

youngjun91 said:


> The spindle diameter of Shimano is 24.0 mm. The spindle diameter of FSA can be 24.00 to 24.07mm. I've read many people having to "persuade" the spindle of FSA into the bottom bracket bearing with a mallet and grease. I chose to lightly sand the inner diameter of my Shimano bearing since I was pressing too hard and it didn't feel good forcing the spindle through the bearing. Then it went it very nicely. There are mechanical tolerances involved so your miles may vary a little bit, by a few hundredths of a millimeter. Shimano spindles are generally a few hundredths of a mm smaller than FSA MegaExo. Read the note at the bottom here: Wheels Mfg BB30A Outboard Angular Contact BB for 24 mm cranks (Shimano) - Black "_Note: FSA MegaExo spindles can be between 24.00mm and 24.07mm in diameter. If your FSA spindle is 24.07mm, this BB will not work! Please purchase our FSA 24.07x37 ceramic hybrid bearings separately."_


The question was posted over 13 years ago. Fully qualified thread dredge.


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## Lombard

Kerry Irons said:


> The question was posted over 13 years ago. Fully qualified thread dredge.


Round of beers on @youngjun91 .


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