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I have a 2012 Mountain Bike with Deore XT. While troubleshooting chain suck on my inner chainring, I figured I'd order a new chainring and replace it. The chainring only has "24-AM" on it. However, I ordered the wrong one:

Shimano XT FC-M8000 Double Chainring 24T, For 34-24T ITEM #CG195A04

The holes didn't line up. So I cleaned the old one and put it back on.

But which one should I be ordering? My searches are returning the incorrect chainring that I ordered. Does anyone know the specific part number I should be ordering?

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Yep, that inner ring has go some nice shark-fin teeth. I predict your photo will be used in future questions about chain ring wear :-) The outer ring looks well- worn too.

An XT equipped bike from 2012 will have the M780 XT series crank which has four symmetrical bolts. The newer XT M8000 series has asymmetrical bolts.

I'm not sure if actual M780 rings are available but there are good aftermarket options for chainrings in general. All you need to know is the bolt-circle diameter (BCD) for the inner ring, which is easily measurable. You should be able to find a replacement with a symmetrical 4 bolt pattern in the tooth count you want at any of the larger online bike component stores.

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  • If the granny ring is "badly worn", then why a new chainring has the same shark teeth? Also, FC-M8000 bolts are symmetrical too, it's just different kind of symmetry. – Klaster_1 Nov 19 '18 at 3:39

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