replacing Bottom Bracket

[signalMTB]

original BB on my 4000 is a Shimano BB-UN72, 113mm spindle with 73mm shell width.  Anyone know if a 70mm shell will work?  What have you guys run on your 4000 or similar?

[willem]

You gotta try a new external BB. The change in stiffness and durability is amazing.
You should be able to get a Shimano M580 or a RaceFace model from an internet seller for less than $150. (Of course that includes BB, Cranks, and Chain Rings!)

The new XBB's are also very flexible with the widths on the BB shells. They come with spacers.

I noticed a huge difference on my 856 single speeder due to the extremes of pedalling with that bike. When you go from knee popping climbs to pedalling like a squirrel on a descent, you really notice the BB and crankset.

For super easy install, go with Shimano. And your LBS should have a few dozen extra wrenches in the shop since Shimano used to ship them with every BB.

[signalMTB]

You gotta try a new external BB. The change in stiffness and durability is amazing.
You should be able to get a Shimano M580 or a RaceFace model from an internet seller for less than $150. (Of course that includes BB, Cranks, and Chain Rings!)

The new XBB's are also very flexible with the widths on the BB shells. They come with spacers.

I noticed a huge difference on my 856 single speeder due to the extremes of pedalling with that bike. When you go from knee popping climbs to pedalling like a squirrel on a descent, you really notice the BB and crankset.

For super easy install, go with Shimano. And your LBS should have a few dozen extra wrenches in the shop since Shimano used to ship them with every BB.

Can you run an external BB with old school square taper cranks?

[shovelon]

Can you run an external BB with old school square taper cranks?

I don't know if anyone makes a square taper BB that way. But would'nt it be cool?

I for one am sold on square taper. Cheap and light, and no squeaks. Ti on Ti works well too.

[willem]

Good question about the square taper...
If you could fabricate a through shaft of the proper diameter and length, with square tapers on the end, I suppose you could do it. Heckuva job tho.

The (evil) genius of the XBB is that it all comes as a kit. You can't buy replacement cranks without the BB bearings.
You can, however, buy new BB bearings for old cranks. (It's kind of like pedals and cleats.)

Maybe it was me, but I always used to develop squeaks in the front end of my drivetrains. (Albeit, I'm a gorilla disguised as a human.) With the XBB's all squeaks are gone.

Good luck, but whatever you do, RIDE THIS WEEKEND!

Will

[jazclrint]

Ok, you cannot use square taper cranks with an external BB.  Raceface makes all of their BBs 70mm specifically so that it will work with both 68mm or 73mm shells.  It just sticks out a little, or is in a little.  So yes, a 70mm will work.  Just make sure you find the directions so that you get the details right.  I have a Raceface Ti ISIS BB on my 5500c.

[Colin]

So, question:
bottom line, can I buy any external bearing "hollowtech" type crank and BB and they will fit any bike? (I'll probably buy Shimano XT)
i.e. the 68x110 XP-X and the 73x113 4000 and Oz?

Or do I need to know any specific measurments as you do with traditional BB's?

These seem to be popping up on eBay cheaper than square taper BB's and it might be cheaper to convert?

Col.

[willem]

Well... "any bike" is a bit of a stretch, but they will definitely fit your 4000.

I saw one set of Race Face XBB cranks with 22 - 32 - Bashguard for $129 in MBA magazine. Yikes!

[signalMTB]

I gotta go regular 73/113 internal as my Double Barrels are old square taper.  

[Tel]

Hi chaps, dont know if these are of any use to us here but they look pretty. http://cgi.ebay.co.uk/HollowTech-2-Bottom-Bracket-Fits-Shimano-Raceface-FSA_W0QQitemZ160175072274QQihZ006QQcategoryZ56193QQcmdZViewItem I assume they will fit and they say else where in the shop that they will have ceramic bearing versions coming soon.
Cheers, Tel.