Shimano external bottom brackets

blacksp20

blacksp20

Likes Bikes and Dirt
I'm in the market for a new bottom bracket as my Shimano SM-BB51 (deore) has finally started making lots of noise.

I've been looking at the SM-BB70 (SLX/XT) and SM-BB91 (XTR) which are a little more expensive, but still not as rich as a Hope or King.

Has anyone used either of these and have any feedback to give?

I don't want to spend the earth on the BB as I am lucky to have the time to ride once a week and can't justify spending $100 on the part right now.

Thanks in advance.
 
Capone

Capone

Likes Dirt
Then aim for the same level BB. no point in spending more when it wont offer that much more performance
 
frenchman

frenchman

Eats cheese. Sells crack.
If you remove the black plastic inserts from the bearings without destroying them and remove the bearing from the BB shell, then you can just buy new bearings from Skf and refit your bearings. Should be no more than $11 per side.
 
blacksp20

blacksp20

Likes Bikes and Dirt
It's not a performance increase I'm after but increased longevity of the bearings.
Does anyone know if the XT or XTR level stuff has better seals or lasts longer than the Deore level?

I'll check out my local SKF supplier and see what their prices are like aswell.
 
muvro

muvro

Likes Dirt
I wouldn't bother with swapping out the bearings. A lot of effort for not much gain in value and the risk of damaging the cups making you spend twice. It's ok if you've done it before, or are familiar with bearings/engineering. But if you haven't got the knowledge or experience, just get a new SLX or XT BB.
 
frenchman

frenchman

Eats cheese. Sells crack.
muvro said:
I wouldn't bother with swapping out the bearings. A lot of effort for not much gain in value and the risk of damaging the cups making you spend twice. It's ok if you've done it before, or are familiar with bearings/engineering. But if you haven't got the knowledge or experience, just get a new SLX or XT BB.
Click to expand...
It's not too bad with the shimano BB. You only need a vice, hammer, punch and a steady hand. Took less than 10 minutes to knock them out and put the fresh set in. I've found the shimano bearings in the slx/hone cranks to be quite ordinary anyway (6-12 month life). I've had the replacement set in there for about 2 years now.

Here's the how to from enduro

http://www.enduroforkseals.com/sitebuildercontent/sitebuilderfiles/hollowtech2a.pdf
 
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PerthMTB

PerthMTB

Likes Dirt
+1 for why bother. I'm all for doing my own maintenance, but when you can get an XT BB online for $18 and an XTR for $23, it just doesn't make sense mucking about replacing the bearings. I just treat BBs as consumables these days, and they get replaced at the annual service together with suspension seals, chains and cassette.
 
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