O.G.I.

Hello guys, I need a little help with a shimano rear deraileur
I have XTR RD-M972 SGS carbon, but I've noticed that the carbon cage has a little crack and I'm affraid that it will broke there:


My old deraileur is Shimano XT M772, so my question is - can I replace the XTR carbon cage with the XT's aluminium cage, or is there any way to reinforce the place where the crack is?
Thank you in advance.
BTW both XT and XTR deraileurs are for 9 speed cassette and both carbon and aluminium cages looks identical.

dsbrantjr

If it is brand new why don't you have the seller replace it under warranty?

O.G.I.

Because it is the last XTR RD-m972 left in the seller's shop, actually I can't find this derailleur anywhere in europe(I've purchased it from a bikeshop from Italy) the seller has already returned me small amount of the money because of the crack.

RubeRad

is that really a crack, or is it just a chip/gouge in the finish from a rock strike? How does it behave if you try to flex the cage with your hands? Derailleurs are not really subject to all that much force. All the force is on the top run of the chain and around the cassette, by the time the chain comes off the cog it's more 'just moving' than being pulled with significant force, so I don't see that riding would tend to cause a derailleur to break there even if it is weakened.

I would just keep riding it if it works.

RubeRad

Also, if the alu cage you have is really the same dimensions as it appears, I can't imagine that it wouldn't work. If you can get it on and get it to shift, you should be fine.

hueyhoolihan

i would ride it. when and if it ever breaks (and there is little reason to think that it would IMO), i would then think about swapping it out.

Soody

Put some epoxy in the crack and ignore it

O.G.I.

RubeRad, it's not a crack, sorry for my bad English I just mislead you, it's a groove into the polish resin, maybe half a millimeter deep, so like Soody said I'll just put some drops of JB weld inside and ride it, hope everything would be fine. I'm not a downhill/freeride biker I do very light cross-country riding, only in dry weather on smooth dirt tracks, so the derailleur won't be put to extreme riding conditions. Thank you guys for all the help

cobba

If needed, the inner cage plate of the 772 is compatible with the inner cage plate of the 972.

https://www.paul-lange.de/support/sh...D//RD-M772.PDF

RubeRad

No problem, we enjoy discussing bikes and parts, that's why we're here! I'm sure, jbweld or not, your RD will perform flawlessly for you for a long time. I just got a hardtail with XTR, and it's fantastic!