XTR octalink compatibility

[Cavalier]

Mattr is correct here.
For Blackspire (DrJo) V2 is the standard although I would write to Blackspire to double check as Shimano were mighty sniffy regarding their Octalink patents (which lead to the rise of ISIS - you know the one I'm talking about!!!!!).
It was a shame that Shimano were sods regarding Octalink as it was basically a hugely improved square taper which should have benefited everyone. Hey-ho.

 

[Benmac]

Apologies if everyone has had more than enough of octalink but I have a question.

I've just nabbed a cheap M950 chainset. It comes with a BB which is useful. I don't have them yet so I don't know the condition of the BB or its length. I do know that its a 68mm though.

I have several frames that it could go on no problem as they have 68mm BB shells (axle length issues notwithstanding. However, the frame I want to put it on is my RTS which is of course 73mm.

Given that the one I'm getting is a 68 as are all the road ones (italian thread notwithstanding) you can still buy new with the V1 splines is there anything I can do to it that would make it fit the 73mm shell? All this is assuming the axle is a suitable length but assuming it is what actually is the difference with the BB itself? Is it just the non drive side cup that supports the cartridge at that end? Perhaps longer on a 73mm BB? As such would the cup off a 73mm BB effectively convert a 68mm BB? Great if it does as while not octalink I think I have a couple of such cups knocking about.

I'm quite happy with mechanics so if some dismantling of supposedly non-maintainable bits is required that's OK, just trying to arm myself with as much information as possible.

EDIT: I've just realised (earlier in this thread) that the proper XTR BB can be either 68 or 73. Just requires different spacers. If so then fingers crossed the one I am getting is a proper XTR one and that it is in decent nick. Even if it doesn't have the spacers you don't seem to need them for the chainline I'll need but a couple of spacers would not be hard to sort if needs be.

 

[mattr]

If you have the real XTR bottom bracket, you don't need any spacers to fit it to a 73. Unless it's an e-type (one spacer, drive side). It's the 68 that needs the spacers.

If it's a sealed road octalink for 68, you'll need (at least) a right hand 73mm cup (deeper/longer than 6 and work out how to get the old one off, some are removeable (easily) some are a pain, some are all but impossible (or moulded in). Using the wrong cup will leave the axle off centre.

The left hand cup you *may* get away with. As it can be wound in as far as you like (the extra 2.5mm isn't a problem.

Probably best posting up again when it arrives (with some pictures).

 

[cce]

If you have the real XTR bottom bracket, you don't need any spacers to fit it to a 73. Unless it's an e-type (one spacer, drive side). It's the 68 that needs the spacers.

If it's a sealed road octalink for 68, you'll need (at least) a right hand 73mm cup (deeper/longer than 6 and work out how to get the old one off, some are removeable (easily) some are a pain, some are all but impossible (or moulded in). Using the wrong cup will leave the axle off centre.

The left hand cup you *may* get away with. As it can be wound in as far as you like (the extra 2.5mm isn't a problem.

Probably best posting up again when it arrives (with some pictures).

it looks like the 5500 and 6500 units have the drive side threads as part of the body.

The DA one looks to be constructed similarly to the M950

 

[Benmac]

Re:

Ta, useful. Once it arrives I'll have a good look and take some snaps.

 

[ishaw]

The da one is practically the same as the xtr unit and has a lock ring on both sides. The axle is shorter so if you can get a longer axle from a donor xtr unit you could swap the da cups over and have a serviceable bb with a 73 or 68 shell.

 

[FMJ]

Shimano were mighty sniffy regarding their Octalink patents

Shimano has the biggest stick (read: lawyers on retainer) in the industry. The only way around their patent was to make something similar, but different enough to skirt it. Even Special Ed won't take them on. They'll only steal ideas from the smaller guys who have less lawyers than them. Works, for the most part.

Oops

 

[Benmac]

OK, my 952 chainset and BB have arrived (actually nicer condition than the pictures suggested so that's a bonus.

The BB is smooth to turn, and marked as a 112.5 M952. All good then so far as that's the right length for the RTS. I've have just shoved the removable cup onto it as far as I can and then measured the distance between the inner edge of both cups. 68mm (thought it was 73 at first).

So, what are my options do you think? My understanding is just put it in as is, that's fine and as shimano suggest. It would only need spacers if being put on a 68mm.

 

[jgjones095]

benmac I've just been through the issue of xtr m950 and BB width!
once fitted the crack wouldn't turn with the supplied 68mm.

I've just had bought a nos m952 bb to get the 73mm length

checkout my Homegrown build blog.
the new bb hasn't been fitted yet. I'm brining it back from the USA.

 

[Benmac]

benmac I've just been through the issue of xtr m950 and BB width!
once fitted the crack wouldn't turn with the supplied 68mm.

I've just had bought a nos m952 bb to get the 73mm length

checkout my Homegrown build blog.
the new bb hasn't been fitted yet. I'm brining it back from the USA.

Oh bum, that's annoying. I'll whack it on I think as a test and see what the score is. Ta.