XTR M952 Short Cage - Maximum Rear tooth capacity

[Christoph2.8i]

Thank you all for the advice and guidance I think I have smaller range 9 speed cassette knocking around somewhere so I’ll swap it over. Thanks

 

[Cloverleaf]

The biggest issue with older mechs on larger cassettes is that the arc of the parallelogram isn't moving in the right line to work from 11T up to xT. Cage size limits the mechs ability to absorb chain slack but the actual mechanics of the mech are what limit cassette size if you want proper shifting. I think the biggest the M952 will have been designed for is 32T - although 34T cassettes were available at that time they were few and far between. 36T was only introduced with 10spd. I used to run a Saint M810 SS on them and they were fine because the arc of the linkage was designed for it.

 

[mior]

I have an xt m750 cassette that's 11-34, so that mega 9 stuff does work with 34t

 

[Betsy]

I've just had the exact opposite issue with the XTR M952 short cage.

I was running 9sp 11t to 34t at the back and 26t 36t 46t at the front, all was gravy, then i swapped the chainrings for 27t 36t 49t and everything at the small end of the cassette would cause the mech to fold over on itself to such an extent, the chain would rub the cage, both above and below, i tried every adjustment inc a new chain which i cut to different lengths, the only thing which sorted it was swapping the GS cage for an SGS cage.

https://www.retrobike.co.uk/threads/xtr-m952-sgs-rear-derailleur-long-cage-only.483497/

 

[wicket]

32t

 

[bold stelvis]

Shimano's "spec" for that mech is essentially 34T max rear sprocket size, but more significantly about 33T total capacity

You MIGHT be able to push a 36T rear sprocket with a longer B screw (or reversing the original one)
I know its not much over the stated max tooth spec but it seems most of the pre dynasys derailleurs (road or MTB) can realistically clear a 34T without too many issues, but thats about the max.

The big issue is likely gonna be the capacity spec (ie total tooth difference front and rear) with you're current setup. With the front triple (20T diff) and 11 to 36 cassette (25 T diff) you're sitting at around 45T which is overshooting the capacity spec for the mech by a very large margin

For sure you can size the chain so that big/big will work without it trying to pull the mech out of the hanger, but its almost certain you won't get enough tension in the smaller sprockets on the granny - maybe even on the middle ring as well - due to the cage being too short to be able to pick up the slack on that much of a tooth difference. The chain will be loose and hanging down and you'll get massive amounts of chain slap unless you're happy avoiding those combinations (which is better than the chain being too small, so that big/big causes actual damage)

Like others above I also have had some success pushing the specs a fair bit - eg I had a 5600 era 105 short cage road mech successfully changing an 11-34 at the back and a 50-34 compact double at the front - but TBH it WAS pushing it to the limit, both in terms of max sprocket size and total capacity and I ended up changing it for an M650 DX long cage which is a lot happier - better chain tension at the extremes.

With either mech, 34T at the back was the max I was comfortable with achieving (which is 6T more than shimano's spec for the 105!) and 36T would have been too much IMO without a hanger extender like the wolf tooth road link or similar. The resultant capacity of 39T was also pretty much the limit of what was possible with the 105 short cage mech (again about 6T over spec) and still being mostly usable at the extremes - but again, there was a lot less compromise in chain tension at the extremes with the long cage DX in.

 

[Christoph2.8i]

Really helpful information here, sounds like it’s not worth trying to make this work as it’ll compromise the performance of the drive train.

I have another smaller ratio 9 speed cassette which I’ll swap over from my Orange Msisle onto this C16-R with the XTR. The MsIsle has a longer cage mech (Newer Deore XT) running a 1x9 set up, so will probably/possibly take this 36T cassette.

Thanks again for all the help and advice.

 

[Retrorockit]

I'm running a mid cage XTR on my 1500W (converted 2004 Gary Fisher Solstice) Ebike. So it's been thoroughly tested. 11-40t cassette.
To do this a longer B screw is needed. Chain length must be just right. Too short and the extra loop on the derailleur cage can get stuck behind the cassette. I linked to a video of it running in the DX thread mentioned above. So 36t shouldn't be a problem.

Your calling it a "short cage" in MTB that usually means mid cage GS, not the road SS cage.But in a 1x situaion 40t has been done with Shimano Zee M640, and Saint M800 both of which did actually come in SS cage for DH racers. My XTR is a lsightly different version than yours.
4t on the cassette = 1 more link needed on the chain (2 teeth)

 

[Cloverleaf]

I'm running a mid cage XTR on my 1500W (converted 2004 Gary Fisher Solstice) Ebike. So it's been thoroughly tested. 11-40t cassette.
To do this a longer B screw is needed. Chain length must be just right. Too short and the extra loop on the derailleur cage can get stuck behind the cassette. I linked to a video of it running in the DX thread mentioned above. So 36t shouldn't be a problem.

Your calling it a "short cage" in MTB that usually means mid cage GS, not the road SS cage.But in a 1x situaion 40t has been done with Shimano Zee M640, and Saint M800 both of which did actually come in SS cage for DH racers. My XTR is a lsightly different version than yours.
4t on the cassette = 1 more link needed on the chain (2 teeth)

There were a few SS M952 mechs made by Shimano mechanics which used the SS Dura Ace cage. I made one myself at the time to run on the M1 but mostly it was GS I ran. SGS was way too long for DH bikes. From memory the M950 long cage sat somewhere between a traditional Medium and Long, and the short cage somewhere between short and medium.

 

[minor_LEGEND]

I've just had the exact opposite issue with the XTR M952 short cage.

I was running 9sp 11t to 34t at the back and 26t 36t 46t at the front, all was gravy, then i swapped the chainrings for 27t 36t 49t and everything at the small end of the cassette would cause the mech to fold over on itself to such an extent, the chain would rub the cage, both above and below, i tried every adjustment inc a new chain which i cut to different lengths, the only thing which sorted it was swapping the GS cage for an SGS cage.

https://www.retrobike.co.uk/threads/xtr-m952-sgs-rear-derailleur-long-cage-only.483497/

Because you added (no doubt) extra chain to allow for the larger outer chainring.

The fact of the matter is, whilst the limits can be exceeded slightly outside of Shimano's recommendations, this has it's limitations.