I have an XT chainset M780 triple on my tourer. All is well. I have just bought a stages power meter which is XTR M985. I was aware that XTR had a lower q factor and i believed i could just space the pedal out with a pedal washer.
However on opening the xtr crank arm it is 22mm deep where it sits on the chainset spindle. The XT crank arm is 27mm. Thus there is a 5mm gap on the end of the axle when the crank is fitted.
The BB shell is 67mm and i have 5-6mm of spacers between nds cup and bb shell and 2mm spacer on the ds.
Given that as i add spacers, i reduce the amount of thread in the bb, is it acceptable to add any more spacers? Is there any other way i can make these two items work together? Any ideas or solutions gratefully accepted.

Thanks

I probably wouldn’t recommend either, but other than getting the correct one, your other option is to space the axle rather than the BB.

That is annoying. I’ve mixed and matched before now.

A 5mm thick spacer on the axle should be ok though. It shouldn’t change the loads on the bottom bracket or axle significantly. As long as it’s snug fitting and seats against the bearing properly.

Appears wheels manufacturing make axle spacers.

Spacers on the axle, that’s how most other 2-piece cranksets work (my Rotor has a 1cm spacer on one side and a .5 on the other).

Your pedal stance will be odd though. The XTR crank should butt up against the BB. The RH XTR crank has a shorter axle.

Can you not return the crank and get the right one?

If I was the sort of person who felt there was benefit in using a power meter I wouldn’t be farting about with increasing Q factor, adding spacers to one side of the axle or fitting BB’s other than as intended – they’d all feel like they were reducing my overall efficiency.

Either get the right Stages arm or change the other half of your chainset to match.

Q factor for XTR is 8-10 mm narrower than XT. So some spacing was going to be needed whatever happened. This just means that the OP only has one option for where to space out.

M985 crank has an 8mm narrower chainline than M980, so pedal placement wouldn’t be miles off. Would be off though.

I’d do as suggested above and make the cranks match.

Do you know for sure that the spline pattern on each will work together? They have differed in the past. Do you get sufficient crank/axle overlap?

Chain line and q factor are two completely different things.

Indeed. No idea why I typed chainline! 8mm narrower chainline would be pretty wild! 😯
I meant to type q-factor hence the pedal placement reference.

I run M980 Stages on M985cranks with no issues at all. I cannot tell any difference on the q factor and that includes 14hr rides.

XTR stages on XT was a risk. At the time I was concerned but elected not to post as I came to it after you had ordered. I remember trying my Stages on my M980 and thinking something wasn’t right.

If I was you I’d either send it back or keep it and look out for an M980 triple crank. There used to be a regular supply of M980 triple rings on here from people buying the cranks for 1x. Unfortunately I haven’t seen any for ages.

I run M980 Stages on M985cranks with no issues at all. I cannot tell any difference on the q factor and that includes 14hr rides

Because they’re exactly the same crank…?

Offset seems different to my eye and as I haven’t noticed any difference in spindle length I’m guessing some of the narrow q comes from offset.

M985 and M980 cranks are different – 985 has narrower Q factor. Shimano tech docs list them with different part numbers.

Thanks for your help everyone. I bought the device as I really want to start using a power meter. due to time of year and the fact I don’t use my best bikes in the winter I thought it would be a good idea to get one on my winter bike/tourer. The idea of ultimate efficiency is slightly muted by the fact that the bike is an 853 tourer that’s heavy and kitted for several day trips, but also serves as my winter bike.

I found this NOS one at a price I could afford, and I thought it would just e a cosmetic mismatch. Come the summer I will probably buy a D/A or ultegra device for the other bikes.

Should anyone be interested I will post some pics of the situation and solution of it works….

I was trying to do it on a budget. I will have a look at the axle spacer idea and see what I can find.

I have a 5mm 24mm ID axle spacer now, so i will try this evening!

did it work?!