Which XT derailleur for a standard 2x10 setup?

[KevinGT]

I didn't realize shimano made so many different rear derailleurs under the same group

I'm building a new bike and want a "standard" 2x10. I thought that that meant FC 785 crank (38-26) and a RD 780 SGS rear derailluer. I want the shadow version. But an LBS told me that that's not the correct rear d. They never said which was correct (this was via email).

What is shimano's current correct rear d for an xt 2x10?

[SimpleJon]

There is not necessarily a correct option - M780 would would work but you may as well get the newer clutch version M786 GS - probably what your LBS meant
GS is medium cage version, get that if running a double unless you can think of some instance where you may need a long cage. They are called shadow plus

[KevinGT]

Thanks for the help!

I don't think I can run the medium cage. I'm using a 38-26 chainring and 11-36 cassette. If I'm adding it up right, that's a 37t chainwrap and exceeds the maximum of 35t for the medium cage.

It's close but I probably should go with the long cage...unless people have had a lot of success running the medium with a 37t chainwrap.

[SimpleJon]

I've not used the Dyna-sys RD's but with the Mega 9 XT M772 I've had no issues running the medium cage with a 44/32/22 and an 11/34 (as long as you don't cross chain ridiculously) - I've always found the Shimano max tooth difference to be very conservative 2 teeth over won't give you a problem with chain wrap in my experience - I would very much expect that you could use the full range - I'm sure others who use the 786 will chime in here

I have a long cage M772 that I sometimes use with an Ultegra group and a 52/39/30 crank and a 11/36 Cassette on my CX bike if I am loading it up.
It's not exactly comparing apples with apples but on the same bike I have had it set up with the med cage Ultegra 6700 RD and an 11/28 cassette which has exactly the same cage length as the XT med cage - max tooth difference is 39 and this is the recommended RD for this setup

Our local trails are Jungle very rooty and plenty of trail snakes - I've had issues with catching long cage RD's before - If you are concerned the long cage M786 will be fine; another issue pre shadow plus was increased chain slap with SGS RD's - the clutch has probably gone a long way to dealing with this.

[Ranger Pride]

Thanks for the help!

I don't think I can run the medium cage. I'm using a 38-26 chainring and 11-36 cassette. If I'm adding it up right, that's a 37t chainwrap and exceeds the maximum of 35t for the medium cage.

It's close but I probably should go with the long cage...unless people have had a lot of success running the medium with a 37t chainwrap.

I would go with the medium cage which is what Shimano recommends for your exact setup. That is what I use and I have had "0" issues with it. I can use the full range of gears in any combo.

[KevinGT]

Thanks. I'm going medium cage.

While I've got your attention, can anyone verify the current Shimano drivetrain component model? It seems the concept of a "group" has flown out the window as each component is on a different version. Here's what I think is current for an XT 2x10 drivetrain:

Crank: M785
Cassette: M771
Front derailleur: M786 (shadow plus)
Rear derailleur: M786 (shadow plus)
Shifters: M780-10
Chain: HG94

Is that current? I'm buying this piece-by-piece and don't want to screw up buying the wrong version!