Shimano mech cage swap

More specifically, does anybody know if we can fit a XT (8100) mech cage to a XTR (9100) body – SGS?

Noticed an ominous crack on the ‘outer’ cage plate of my girlfriends rear mech (looks like it might be carbon). Replacement is £90 but a XT plate is £18 – she’s not a gram-counter so downgrading to alloy would not upset her.

With the older XTR mechs the cage spring was in a different place to all other mechs so needed a hole in a different place, worth checking if it’s still the case otherwise it would need an extra hole bodging

SJS Cycles website is good for this sort of thing with Shimano – they indicate what is an A match (same) and a B match (compatible).

In this case, it appears that the inner plates are compatible but the outer plates not. Few differences are apparent in the photos, but some of these could just be due to the different material:

https://www.sjscycles.co.uk/gear-spares/shimano-deore-xt-rdm8100-outer-plate-assembly-sgs-type-y3fw98080/

https://www.sjscycles.co.uk/gear-spares/shimano-xtr-rdm9100-outer-plate-assembly-sgs-type-y3fa98080/

The compatibility information comes from the official exploded diagrams, which SJS link to:

http://www.sjscycles.com/Drawings/Shimano/Shimano_Deore_XT_RD-M8100-SGS_Tech_Doc.pdf – this M8100 document has a M9100 compatibility column.

Same doc for M9100 – http://www.sjscycles.com/Drawings/Shimano/Shimano_XTR_RD-M9100_Tech_Doc.pdf – note that the bumper that goes against it is a different part too.

So, not officially at least.

Thanks @bikesandboots – I had already spent a while staring at those documents but couldn’t actually see from the diagrams much difference – hence the question. The “pin” and “bumper” are separate parts and looking at the GF’s XTR it is likely because the plate is carbon (so pin cannot screw directly in – which it does on the XT) – unsure about bumper.

I think we will give the XT plate a go and report back. Plan B is to re-inforce crack with epoxy

Hi @vmgscot,

I’ve landed here with the same issue you posted about.  My plastic(carbon) XTR outer cage needs replacing and I’d like to swap in an XT outer cage made of alloy instead.

Did you try it? Did it work?

Thanks

Yes, @stephank the XT plate did fit and work…. right up until the GF clattered the mech of a rock while on holiday last year!

She now has a Deore mech fitted.

Perfect. Thank you.

I’m going to try swap to the XT outer cage then.