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What bottom bracket is compatible?
NB: Originally posted elsewhere on the Global Riders Network and appears via syndication.
I did a bit of an overhaul on my bike this afternoon and noticed the cranks were a bit stiff to turn, after further investigation it turns out the right hand side BB bearing has seized. As I'm up for a replacement, I thought I may as well upgrade at the same time. The only problem is, I don't know how to read the markings and work out what size I'm looking for. Here are a couple of pics, if someone would be so kind as to de-code them for me. 
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FSA Megaexo 24mm Diametre BB-7000
www.fullspeedahead.com/products/60/BB-7000-(MTB)
Hi
I've used alternative bearing kits in FSA cups like yours a few times now as the original Megaexo ones turned out to have a pretty short life expectancy.
Apparently there is a few microns of difference in the crank shaft diameter between Shimano & FSA but many aftermarket bearings are the same for both & you don't see it mentioned in aftermarket BB literature.
Oh, & I've had good longevity out of both Hope & Std Enduro kits with FSA cranks so I don't personally go along with the info below.
Note the spacers used either side & refit accordingly.
http://www.chainreactioncycles.com/Models.aspx?M...
http://www.chainreactioncycles.com/Models.aspx?M...
From the Enduro site (DIY MTB)
Enduro Outboard BB Kit - CH 5 - FSA
Outboard bearing upgrade kit for FSA with marginally larger crankshaft
Ceramic Hybrid grade 5 bearings and outer seals
Note: There is only ~07 mm difference between the crankshaft sizes of the FSA variant. However because our bearings sit directly on the crank this makes it impossible to correctly fit our standard BB upgrade bearings. it is important to be able to determine which size FSA crankshaft you have before ordering. Please contact your bike shop or us to ensure you get the right kit.
$71.94
Thanks for the info, guys.
It seems there is no direct upgrade for the BB unit then? I thought it would just be a case of taking mine out and putting a better model in. Not so simple it seems!
I'm not sure about running bearings that are the wrong size though?
Tony, would the MRP BB you linked to be a direct replacement and if so, how can you tell?
If I ever replace bearings in a BB or my frame I pull them out first and take them to my local bearing supply shop. That way I know I am getting the right sized bearing.
You can always just buy a new BB which is alot easier.
"You can always just buy a new BB which is alot easier."
Ideally, that's what I would do. But an upgraded version of what I have now, I just don't think there is a straight upgrade.
Why not??
It looks like a standard external BB
What cranks are you running? and is it a 67/73mm bottom bracket??
While FSA cranks are nominally 24mm on their external bearing units, they are enough different (couple of hundredths of a mm) to not fit properly in other brands of 24mm bottom brackets (eg Shimano XT).
FSA BBs are universally crap. I changed my cranks to XT. Problem solved. When that BB dies (if it ever does) I'll whack in a Hope
Edit: covered in more detail by Tony above... derp
Depending on condition of your current crankset , I'd be sorely tempted to get a new slx crankset for $130 or deore for $80 - you get new bb, and new cranks and rings. Wasteful ? Sure - but an opportunity to bling (for slx anyway )
Edit - assuming of course you don't already have a blingy FSA carbon job
I currently have an FSA Comet crankset. With the following markings on the inside of the crank arm:
I'd not thought of getting a whole new set. There's nothing wrong with my current set, but if it's going to be a pain to upgrade or I have to keep replacing the OEM BB every 8 months, I'll look into that option. BTW everything else on the bike is XT.
Thanks again everyone for your help, it's much appreciated.
If you're in Perth & want to try cups fitted with Enduro bearings get in touch next week & we can give them a go.
I've the necessary tools & know that I've got a few 24mm external sets around.
If all is good I'll expect a beer if they're no good we'll have gained knowledge.
I rate our chances at 90% plus though as I already have an FSA Afterburner crank running smoothly on std Enduro bearings here.
Btw, I tried bearing suppliers previously for the bearings only but the ones I tried couldn't source them, also the ones that use plastic "Top hats" between the shaft & bearing usually cannot be replaced without damaging the plastic part.
I linked the MRP BB as its a straight 24mm id external BB for 68/73 frames, in other words about as common & universal as they get.
You can even get ones like this to work with the quirky two different size Truvative GPX set up by using a Hope adaptor.
Nothing's ever straight forward!!
T
Thanks for the offer, Tony, but I'm in Sydney.
There's a bearing place near me so I'll try there in the next week or so and let you know how I get on.