I’m prepping a bike for a mate’s Mrs. She struggles with hills, so putting a 36 cassette on her Trek girly road bike (tiagra triple up front).

This used to work reliabliy on 9 speed stuff.

With 10sp I can get a tiagra 30 tooth cassette to work.

When I try to go to 36 teeth, deore mech (as tiagra only does 30 teeth), it seems to not index correctly.

Any ideas?

Is the deore mech a 10spd one? You’ll need to use a 9spd one as Shimano road 10spd uses the same cable pull ratio as Shimano mtb 9spd.

36 is quite a stretch for a 9sp mech – works but it is a bit close and you have to set q carefully IMO/OMB*

(*on my bike)

SDB +1

Is the problem that the top jockey is kissing the 36 sprocket or is the problem that it’s not indexing properly?

Firstly, you need a 9spd MTB mech, which it sounds like you have (Deore)

If the problem is the indexing then officially a 9spd MTB mech and 10spd road shifters are compatible. However, in practice they aren’t quite. I’ve fitted this setup on four separate occasions and they’ve all resulted in overshifting:

setup 1 – Ultegra 10spd STI, LX 9spd MTB rear mech
setup 2 – R770 10spd shifters, XT 9psd mech
setup 3 – 105 10spd STI, XT 9spd mech
setup 4 – 105 10spd STI, SLX shadow rear mech

and on all these setups, the mech was overshifting.

With the first three setups I was able to reduce the pull ratio by re-positioning the inner cable, further away from the pinch bolt, but this is a DIY bodge. Out of the box there is a definite overshift problem.

I’ve run 105 shifters and a 9-speed XT rear mech with no problems whatsoever – in fact, my Sutra came with that setup.

I now have Ultegra shifters and a 9-speed mechs on my Amazon and again there are no problems at all.

I’ve a 10speed cassette (of course)

The Deore is a 10speed (thought I’d played safe there!)

Thanks simondbarnes and others, I can nab a 9sp XT and try it. I’ll feed you guys info back. Current wisdom above suggests:-

Overshifts
setup 1 – Ultegra 10spd STI, LX 9spd MTB rear mech
setup 2 – R770 10spd shifters, XT 9psd mech
setup 3 – 105 10spd STI, XT 9spd mech (maybe, difference of opinion above)
setup 4 – 105 10spd STI, SLX shadow rear mech

Works Fine
setup 5: Ultegra 10sp STI, XT 9sp rear mech

my road bike has a rapid rise xtr mech on it and ultegra 10edit: 9spSTIs – works fine (from your list above, I don’t see why the lx shouldn’t work if xt does – and same for ultegra vs 105). My cross bike had 105 stis and a deore mech – fine

my mtb has ultegra flat bar shifters 10sp and a conventional 9sp mtb mech – seems fine but not yet stressed it much

maybe I’m not able to detect these minor imperfections (or else they only come into play at 10sp and I’m going to suffer with the mtbthis summer)

are you 10speed Druidh?

Been there. Tried it, although not on a road bike.
10spd shifter really needs a 10spd mech due to cable pull ratio. Will work for about half the range but then goes out of sync.

🙂
I’d started designing with a spring to go at the outer cable end, to adjust the cable pull. But gave up & bought a 10spd mech.

10 speed cassette on my Amazon but the Sutra was 9-speed…. my bad.

Further to the advice above, to work with a 36T cassette you MUST have a shadow rear mech (or bodge the death out of a non-shadow one).

So you need 9 spd and Shadow to work with your 10 speed.

10spd shifter really needs a 10spd mech

I think you may have got the wrong end of the stick there. Sure, 10spd MTB shifters need 10spd mechs but the OP was talking about 10spd road shifters, which need a 9 spd mtb mech (officially).

My original comment stands though. If I’d tried it just once then it may have been an unusual outcome, which you could dismiss as strange, but I’ve tried it four times and they were all overshifting, so it’s not an aberation, it’s a structural fault.

I actually made my own altered pinch bolt thing, to solve the problem 😉

Nice one.

setup 6: Tiagra 10sp STI, XT 9sp rear mech (med cage, brand new). B-screw into its max. I like to see 2 clear links between cassette & mech, but it works well.

The lady road tested it today and is happy, better than original.

Thanks everyone. I was scratching my head there for a minute (well 1100hrs-0100hrs).

Just out of hospital after ACL recon surgery so fancied easier gears on my road bike for when I can ride again. After a bit of “Caracticus Potts” in the garage I’ve now got the original Ultegra 10 spd shifters, a 2nd hand XTR M952 long cage rear mech, and a SRAM pg1050 11-32 running on the back of my compact Roubaix and it works like a dream – faultless shifting across the entire range. My neighbour is a “serious” road cyclist and has just done a 30 or so mile test ride on it for me today with no issues at all.