# Shimano XTR 9 speeds RD-M970 rear derailleur & XTR 9 speeds 11-34T cassette ???



## edle (Mar 25, 2013)

I have a Shimano XTR 9 speeds RD-M970 rear derailleur(short cage) and would like to use it for a XTR 9 speeds 11-34T cassette.

Is it a workable combo ? Or do I need a RD-M971 instead ?


----------



## cxwrench (Nov 9, 2004)

edle said:


> I have a Shimano XTR 9 speeds RD-M970 rear derailleur(short cage) and would like to use it for a XTR 9 speeds 11-34T cassette.
> 
> Is it a workable combo ? Or do I need a RD-M971 instead ?


Max cog is 34, so that's good. Capacity is 33, so you need to figure that out.


----------



## CleavesF (Dec 31, 2007)

When it comes to MTB derailleurs, never buy short cage.


----------



## edle (Mar 25, 2013)

cxwrench said:


> Max cog is 34, so that's good. Capacity is 33, so you need to figure that out.


'Capacity is 33'....Do u mean the front chainring max. is 33T ?


----------



## cxwrench (Nov 9, 2004)

CleavesF said:


> When it comes to MTB derailleurs, never buy short cage.


That's just stupid. If the spec is correct for the application, why not? 



edle said:


> 'Capacity is 33'....Do u mean the front chainring max. is 33T ?


No..."capacity". The difference between the small cog/large cog + the difference between the small ring and large ring. For example:
11/34 cassette: difference is 23 teeth
50/34 compact crank: difference is 16 teeth
23 + 16 = 39 which is obviously more than the capacity of 33 for the GS short cage derailleur. You'd need the SGS long cage, which has a capacity of 43. 
If you were running a single chainring you'd be fine w/ the GS and it's shorter cage, contrary to the incorrect advice provided by the other guy i quoted.


----------



## edle (Mar 25, 2013)

cxwrench said:


> That's just stupid. If the spec is correct for the application, why not?
> 
> 
> 
> ...


Thanks for the valuable input.
Yes, I'm planning to run a single ring(28T or 32T) in the front.


----------



## Cinelli 82220 (Dec 2, 2010)

970 is Rapid Rise, 971 is regular small cog normal.

If you are sure you have a 970, then get a 970 with a longer cage, not a 971.

I use a 971 short cage on my commuter. 44/30 985 crank and 12/27 DuraAce cassette. Works great.


----------



## Jimjaps (Jun 17, 2021)

cxwrench said:


> That's just stupid. If the spec is correct for the application, why not?
> 
> 
> 
> ...


So what if i use it in my 1x setup? Can i use it with 11-40t? Maybe add a goat link? I have a 40t chain ring(1x) with a 26er bike,,,
Thanks


----------



## cxwrench (Nov 9, 2004)

Use what? You have the same derailleur? No, it won't work w/ a 40t cassette. As I posted 9 years ago the max cog for that derailleur is a 34t. I'm not a fan of any kind of derailleur hanger extending 'link'. They will get the upper pulley to clear a bigger big cog but they pull it away from the smaller cogs and shifting suffers.


----------



## 202cycle (Sep 13, 2011)

The recommended reading section at the bottom of these pages sure does turn out a ton of thread dredge.


----------



## cxwrench (Nov 9, 2004)

Damn, it does. I've never noticed that.


----------



## Lombard (May 8, 2014)

cxwrench said:


> Damn, it does. I've never noticed that.


Me neither. That would explain the increase in thread dredges since the site upgrade.


----------

