XTR M952 chainring rot

[rwm1962]

I put my bikepacking ride on the stand knowing it needed a sticky rear mech fixing & new limit screws fitting on the front but I was gutted to find so much corrosion on the chainrings. It was cleanish last time I rode it maybe 18 months ago. Nearly all of the finish on the middle & small chainrings has flaked off & the middle one has delaminated & spread so the chain can't run on the grannie ring. Is this a common issue?



These chainrings seem hard to find at a reasonable price but I was able to find a complete crankset in great condition. Bike is now running sweet but if it happens again I'll be looking at a more economical replacement - maybe something more recent or modern. I'd like to stick with 3x.

 

[ishaw]

Jeez I've seen the finish flake off, tends to be middle ring, but I've never seen anything like that before.

What's the black stuff on the middle and outer?

The most economical option for these cranks is to change the outer ring/spider to a spider that can take whatever ring you want. Most 'common' are 110 BCD and were offered as standard but aftermarket options are available. You can also get 104 BCD and 94 BCD too.

I've probably got a spare 110 BCD if you are looking.

 

[rwm1962]

Thanks @ishaw - that's good to know! I'm hoping these will last me a few years but I'll go down the replacement spider route when required. No rush - but if you have a decent spare I'd be interested. Is it just a spider to which you can fit 3 rings or is it like mine - intergrated outer ring & spider?

The black marks are just tarnish.

 

[ishaw]

It looks like the rings are made of coal. Bizarre.

And yes, it's a spider that replaces the outer ring, so you can fit any combination of 110 BCD rings. I even have a nos outer m952 ring for the job.

 

[rwm1962]

Aye - inner & middle ring have gone really granular. Outer ring is fine bar the minor tarnish marks. What surprised me was the middle ring splitting - looks to be 2 parts bonded together that have now started separating.

 

[bikeworkshop]

Gawd that looks awful.
Aren't the ramps plastic bonded on?
I think we have loads of those rings, a colleague of mine kept ordering them by mistake and they don't fit much else than xtr 950s

And have you ever ridden on salted roads?

 

[rwm1962]

If the rings (24T & 34T) are modestly priced I could be interested otherwise I will go for a different BCD spider!

Not sure about the bonding on the middle ring but it has failed spectacularly! I did use it for commuting over winter of 2022/23 3 days a week & about 6 miles on road out of the 22 mile round trip so maybe salt was an issue. It was then hung up until now - it wasn't spotless but it wasn't glopping.

 

[ishaw]

Gawd that looks awful.
Aren't the ramps plastic bonded on?
I think we have loads of those rings, a colleague of mine kept ordering them by mistake and they don't fit much else than xtr 950s

And have you ever ridden on salted roads?

As far as I know, they aren't bonded.

If you have a load nocking around then I'd be up for one or two as I have a few xtr m95x chainsets on bikes I'm not looking to part with ever, but would like to ride them (more) and keep them running with a stash of spares.

 

[rwm1962]

It was only the chainring bolts holding the middle ring together

 

[greencat]

That's the next Shimano scandal right there....only about 20+ years too late