Are Shimano cartridge BBs serviceable?

larrydj

I am wondering if I can safely take apart and reassemble an XT or XTR cartridge type bottom bracket. (ES-71 XT and M952 XTR)

Here's why:

I have a FSA mountain bike crank that requires XT octalink spindle, not XTR. The XT is significantly heavier than the XTR, though I believe the spindle weight is the same. (they are both hollow cromoly). They just have a slightly different octalink spline. I was thinking of taking the XTR spindle out, and placing the XT spindle in. 40 grams less. Can this be done, and what would I have to do to do this? I have never seen anything on servicing the internals of a Shimano cartridge type bottom bracket.

Juba

You are about 10 years too late for Shimano bottom brackets that are in anyway consistantly servicable. Way back, they had a lock nut threaded onto the spindle, right at the seal to the shell. Mind you, I beliece that was for their lower end bottom brakets anyhow.

Now a days, the service instructions for a Shimano bottom bracket reads like this:

Step 1 - Remove old bottom bracket.
Step 2 - Open lid of trash can and throw old bottom bracket in.
Step 3 - Take new bottom bracket out of box.
Step 4 - Install new bottom bracket.

You can get them apart if you brute force it, but you are going to mangle parts doing it. And, Shimano does not sell replacement parts for any components that are designed as sealed units.

Cheers,
Juba

larrydj

Hmmmm......

I had assumed that anything that was once assembled could be disassembled throught he reverse process, but I guess that isn't always the case. I was thinking of using the sealed M952 XTR BB, but I did see that the M950 is serviceable. So if I mangled a XT BB by taking it apart, but the spindle was unharmed, I could then put the spindle into the M950 BB. I don't care about the XT BB except for the spindle.

The flip side to the M950 being serviceable is that it is not sealed, so I worry about the reliability.

Juba

If you are determined to give this a go, I might suggest picking up a lower end Shimano Bottom Bracket, say a Deore level one for like $20 to rip apart first. Use it only as a test modle, hell even take a hacksaw and chop it right in half. With it apart, you should be able to get an idea of the basic bottom bracket assembly that Shimano uses, and would give you some advance intel on how to tackle taking the more expensive one apart.

Cheers,
Juba