So picked up a second hand XT chainset. Took the old SLX off and noticed on the drive side there was a (perhaps 2mm) spacer type thing on. I just assumed the new one didn’t require one so installed and been fine for a couple of weeks. Today noticed the drive side had come loose so I’m now thinking this spacer was perhaps missing on the 2nd hand XT and actually important?

Anyone know if its possible to buy this part? Is there part number?

is this your bottom bracket spacer?

That is frame dependant and depends on your BB sheel width. Frames are normally 68 or 73mm, the 68mm need 3 spacers in total (normally 2 on the drive side and 1 on the node-driver side) and 73mm 1 spacer (normally placed on the drive side).

Spacers are 2.5mm hence the 2 more needed on the 68mm shell.

Is there part number?

even if there were you’d need to be clear about which XT chainset you have.

Yeah, true. It’s actually XT FC-M785

No Andyl (it’s PF anyways) the actual crank not the BB

On the SLX I took off, over the chainset axle on the drive side was a spacer/washer. There wasn’t one with the the XT FC-M785.

I’ve just removed and cleaned the bolts on the non-drive side and put a dab of loctite on. It’s quite possible the spacer isn’t required and due to lack or a torque wrench, these weren’t as tight as they should have been.

A spacer on the crank axle or do you mean on the BB?

Measure your BB shell width and then see how many spacers you have between the BB cups and the frame. Never had a spacer on the actual axle but only had LX, XT and XTR cranks.

Ahh FFS in original post, it was the non-drive side that had come loose. Just got back from work and was hypo and trying to write a post. Looking back, it wasn’t the most perfect of paragraphs!

I’ve just removed and cleaned the bolts on the non-drive side and put a dab of loctite on. It’s quite possible the spacer isn’t required and due to lack or a torque wrench, these weren’t as tight as they should have been.

Are you gently nipping up the plastic end cap on the none-drive side with the correct tool to pre-load the bearings and then tightening up the arm clamp bolts?

Ahh FFS in original post, it was the non-drive side that had come loose. Just got back from work and was hypo and trying to write a post. Looking back, it wasn’t the most perfect of paragraphs!

yeah it wasnt the clearest 😀

By spacer do you mean the plastic thin in the clamp bit of the non-drive arm? This is a little plastic thing with a pin to locate into the hole on the splined area of the axle to stop the cranks sliding off (needs to be flicked up to remove arm and has one complete hole around one bolt and one open edged hole around the other clamp bolt to allow it to flick up).

You should push the arm on, click down this spacer, tighten the plastic pre-load cap gently and then tighten the arm clamp bolts. You don’t want to overtighten the arm clamp bolts as that will just distort the arm on the splines and it will never clamp right again. The arm should not clamp down on the black plastic bit in the clamp, if you are tightening it that much you have gone too far.

No Andyl (it’s PF anyways) the actual crank not the BB

On the SLX I took off, over the chainset axle on the drive side was a spacer/washer. There wasn’t one with the the XT FC-M785.

ahh this must be a push fit thing. Probably need the spacer then. Not used one of those so can’t advise on that. Only used screw in BB’s where the spacer goes on the BB thread. Quite plausible you need a spacer on the axle with a push fit BB.

SLX and XT axle width between the arms should be the same.

Yeah, damn diabetes. I often try to do quite complex things (like form sentences) while hypo.

Yeah it’s a PF bb on a Giant Trance, with a second hand XT FC-M785 chainset running a single AbsoluteBlack oval ring.

I think I’ll take the CS off my hardtail, steal the spacer and put it on the Trance and scour the interwebs for a replacement (hardtail can suffer while I find one!)

andyl – Member

Are you gently nipping up the plastic end cap on the none-drive side with the correct tool to pre-load the bearings and then tightening up the arm clamp bolts?

Well…. not with the correct tool (used a 5c piece!) but it’s nipped up and pre-loaded before the crank arm bolts were done up.

Shimano cranks (at least the ones i’ve had) have all had a thin spacer on the inside of the non-drive side crank arm. When the cranks are put on this spacer is what butts up against the BB.

Not super sure why it’s there but I know on some older cranks i’ve had that when i’ve lost this spacer (or it breaks) then the crank arm tends to slowly work it’s way loose over time.

Oh, are you sure it goes on non-drive side? That’s interesting as mine was installed (had a shop fit the BB and SLX chainset initially) on the drive side?

Not sure no it’s just what all mine have come with, including the new 11 speed cranks. Check the non drive side arm, if there is a small groove on the inside of the arm this is where the spacer i’m talking about goes. I’ve never noticed any spacer on the drive side, you can see the spacer on the non drive side arm in this pic:

there is a little ring spacer that looks like an o-ring but is quite rigid plastic in a groove on the non-drive side crank arm. Slightly bigger diameter than the axle IIRC and I think is just there to interface with the bearing.

Sounds like the OP has missed off a simple axle spacer which is the equivalent for push fit that BB cup spacers are for screw in BBs to account for BB shell width.

Perhaps the easiest way is for the OP to look at this document
http://si.shimano.com/php/download.php?file=pdf/ev/EV-FC-M8000-3849A.pdf
And say whether it is Item 5 or Item 7

Was thinking on the way home from work the spacer was probably supplied with your BB not the chainset so you should have kept hold of it and not got rid of it with the slx.

2nd post here mentions a 2mm spacer for push fit:

http://www.mbr.co.uk/forums/showthread.php?11574-Press-fit-bb-sticking-out

The SLX that came off had part 5 “ring” so that’s what I need.

$10 on eBay X|

Or £2.99 from SJS

I believe that part “5” is only a thin ring, not 2mm as per the OP. I think it is a seal that fits into a recess on the inner face of each crank arm – there should be two of them – one for each arm.

If the spacer looked like this:

There will only be one of them and it comes with a press fit BB, not the cranks.
(Ignore the rest, it’s not a shimano crank set)

there should be two of them – one for each arm.

There will only be one of them and it comes with a press fit BB, not the cranks

So one or two???

IIRC there was only one on the drive side on the SLX I removed, unless the non-drive side remained attached to the BB when I took the crank off?

So one or two???

Depends what’s missing…

The part in the SJS link is item 5 in the exploded drawing. There are two of them – one in each crank arm. They are thinner than 2mm. Is there one in your NDS arm already? Is there one in your DS arm? Do they look like the spacer you took off?

If the spacer looks like the one arrowed in my picture above, you only need the one, but it’s supplied with the bottom bracket, not the crankset.

Did you take the cranks back off and check for the little thin black rings? They very rarely come loose so should be there.

Not yet, been gardening all weekend :/

OK found it. Bottom of parts bin! Fitted to drive side as it was with the SLX (which is on the hardtail with a non-PF bb). On the XT you can see where it was meant to be but there was no marks or wear on the non-drive side so can only assume there was only one originally.

We shall see how things pan out. Can’t ride it anyway as the rear brake seems to need a re-bleed as the lever’s pulling all the way to the bars and needs a few “pumps” to get any bite. Yeah, XT :/