Shimano Bottom Brackets

Info seems to be scarce on the webz so I appeal to the NSMB fount of knowledge!

For external/Hollowtech II BBs:
Is there a difference between an Ultegra and an XT(=SLX/Zee) BB?
What is better about an XTR BB?
What is different about a Saint BB other than the gold?

Thanks, Ben

Pretty sure there is a dimensional difference between road and mountain Shimano bb's. Not cross compatible as far as I know.

The XTR BB is hands down the best BSA BB on the market. Don't know what voodoo magic they have in them, but I can run these for 2-3 years before replacing them. I swapped mine from trail bikes to DH bikes and back again and it keeps on going like new. For about $80 (???) at a LBS, that's good value.

The Ultegra BB won't have the same durability due to sealing, nor will it come with the right amount of spacers or proper width inner shell (which is a critical part to help longevity).

The difference between road and mountain BB's is the amount of thread in the frame, mountain has more and the bearing width, again mountain bearings are deeper.

Saint BB cups have more thread than XT/XTR and screw into the frame more, so better for harder use. Bearings, seals etc are the same as the XC/trail versions.

Durability of the bearings varies widely from person to person. Some people get years out of standard BB's, others only a couple of months. The most durable and servicable BB on the market is the XD15 from Enduro. Not cheap, but it leaves the others in the dust for performance, durability and ease of maintenance.

I was running BB70 HT2 (Deore / SLX / HT unit) on SLX in 73mm shell on last bike

and running Ultegra HT2 on Tiagra cranks in 65.5mm shell (cut down) on current road bike in 1 x 10 with chain device

the road HT2 BB does not use any spacers between BB shell and HT2 cups (this is why the 68mm shell was cut)

the mtn HT2 BB has 1 driveside spacer for 73mm

and 2 driveside / 1 non-driveside spacers for 68mm setups

something else I would add, as a pro wrench that has installed 100s of Shimano Deore, SLX, XT, Saint HT2 cranksets; is that proper frame preparation and good set up is critical to durability:

-chasing the threads and facing the BB shell

-Shimano anti-seize on the BB shell threads, centre spacer tube o-ring seals and on the crank axle (I dump some on the driveside bearing when installing the crank as this pushes anti-seize through both bearing inner races and covers the axle interface)

-never over tightening the bearing pre-load cap (there is a good reason both the cap and the Park tool are made from nylon) its only a couple nm, not 15nm…

-blue loctite on the twin pinch bolts and both bolts set to 13nm with torque wrench

if the crankset ever comes loose (it should not if installed properly) then not "ignoring" the issue but removing and refitting as above ;)