XT/XTR rear mech + 11-25 cassette?

Especially for light weight issues concerning cyclocross / touring bikes & parts.

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vinuneuro
Posts: 103
Joined: Mon Mar 06, 2017 10:34 pm
Location: Chicago

by vinuneuro

I want to do a 1x mechanical or di2 setup with a mtb clutch derailleur. Shimano says 40T is the minimum size for the large sprocket. Anyone have experience using a compact road cassette with the XT/XTR rear derailleurs?
'16 Spec Diverge Expert

vinuneuro
Posts: 103
Joined: Mon Mar 06, 2017 10:34 pm
Location: Chicago

by vinuneuro

Found this video from Gravel Cyclist who tried this with an 11/26. In the comments he said it took lots of tweaking of the b-screw but it's pretty obvious the shifting is sloppy going up the cassette. Looks half-way ok because of Di2, but would be a disaster with mechanical.

https://www.youtube.com/watch?v=A5Hkv77ZM3o

Looks like it will be an Ultegra RD + chain guide for me.
'16 Spec Diverge Expert

ooo
Posts: 526
Joined: Sat May 21, 2016 12:59 pm

by ooo

I was using 11-28 for about half year with FD, it was OK, but can be better.
Without FD it will be better, because it is possible to setup pulley closer to cassette.

for mechanical it is pretty easy -

you can use 10 speed mtb rd in place of 11 speed mtb rd (they have same pull ratio),
10 zee or saint mtb rd have road cassette mode and clutch
so you can use 11 speed mtb shifter (or road shifter+tanpac converter) + zee/saint in road mode + 11-25 cassette perfect shifting

for di2 it is not easy, because rd geometry is not optimized
there are 3 differences (to convert new XT to old XT design/Saint geometry):
1) on old 10sp mtb rd (and new R9100/R8000 road RD) pulley on the same axle as outter plate axle
to fix this you need 10sp XT cage + drilll a new thread for stopper pin (I havent tested it yet) + make spring hole a little bit bigger (tested)
2) after you change plate to old style you will have pulley more upfront away front cassette
I haven't tested it, I think it is not a problem for shifting. but it requires more clearance from chainstay tube (if chainstay tube is not straight)
3) RD (spare) bracket or frame (spare) hanger can be modified to move RD closed to a cassette using SAINT/ZEE design solution
(I have tested it without changing cage - it didn't help because of pulley axle geometry; I have to test it again after finishing 1 and 2)


Image


alternative solution, easier and compatible with non-straight chainstay tubes, but more heavy (on the front and rear):

to make custom tight spacing cassette with big cogs, like this:
13-36 or 14-36 (may be 13-32 or 14-32 for your 11-25 cassette)

link to thread about 1X-36 11 speed cassettes:
viewtopic.php?f=3&t=148480

Image


the best and hardest solution from motorapido: use ultegra RD and build your own clutch

viewtopic.php?f=4&t=146681&start=15#p1337337
'

vinuneuro
Posts: 103
Joined: Mon Mar 06, 2017 10:34 pm
Location: Chicago

by vinuneuro

Thanks ooo! The Saint/Zee + Wolftooth Tanpan looks like a promising option. Is there any downside with such a setup over using a road rear mech?
'16 Spec Diverge Expert

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