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  1. #1
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    XTR RD-M980 vs RD-M981? Which derailleur do I need?

    Can anyone help me understand the difference between the XTR RD-M980 and RD-M981 rear derailleurs? I have searched the 'net and can't seem to find a clear explanation of the difference between these two. Shimano's website returns nothing when searching on the RD-M981. Is that a newer version of the RD-M980? It is strange that there is no mention of this on the Shimano site.

    I am looking to replace my SRAM XX derailleur on my 2011 S-Works Epic with XTR. I have 22/36 chain rings (X0) and an 11-36 XX cassette. I presume this means I need an SGS long cage. Which is the best option for an XTR derailleur? RD-M980, M981, M985, M986? I'm stumped. Any help is appreciated.

  2. #2
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    The first two are older models the one u need depends on how u ride (trail rider or race) The race stuff doesnt hold up under alot of trail riding. So more than likely u want to get the XTR RD-M985 has the new clutch which reduces chain slap. Yes u need SGS long cage.

    Another good choice is Zee M640 its medium cage(works on 36 tooth cassettes) that won't get bang up like the long cage. I have 3 of these on my bikes.

  3. #3
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    Thanks! M985 it is. I am a bit of a weight weenie though so I am wondering if the clutch mechanism is worth the additional 30-something grams? Will have to do some more research...

  4. #4
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    The M980 (no clutch) and M985 (Clutch) were from the same series and are older that the M981/M986. The M981 replaced the M980, and similarly the clutch based M986 replaced the M985. From what I understand the changes were small and mainly the 981/986 allow the removal of the B-Pivot for a direct mounting. XT had a similar change M780 - M781. All new Shimano Shadow's are direct mount compatible and work if you have a frame that supports it.

  5. #5
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    Late reply but yes I'd say the clutch is worth it. It is considerably less noisy on rough descents. Chain slap being less of an issue lets you stay in an easier gear which in turn means less shifting when the next climb comes.

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