It’ll be fine
Or so I assume ’til I saw the above.
I went 9-10 speed on my cx bike using the same rear mech – are you sure??

well, that’s sorted then.

I must confess I thought cable pull was dictated by the shifter not the mech?

MTB 10 and 9 speed use different ratios
Road 10 and 9 speed kit use the same ratio.

This is not from experiance but what i have been told.

the pull ratio is irrelevant for a mech – all that matters is ‘will a 9 speed chain fit through a 10 speed mech without bashing anything?’

www, how will the shifting work if you replace a mech that moves 2mm for every 1mm of cable pulled to a mech that moves 1.8mm for every 1mm cable that is pulled?

I think that the ratio is important but that is just me.

Hobnob and wwaswas- not the case. What Sssimon says is correct, the new rear mechs have a different leverage so for the same amount of cable pull a 10 speed mech will move less than an old 9 speed one. Just like a Sram rear mech and a shimano shifter- you click the shifter and it’ll move a different distance to a shimano mech with the same shifter.

This is from experience and what Big Al at Shimano has told us in the shop.

I have a 9speed mech and a 10 speed shifter and have to use a pulley to alter the amount of cable pulled for it to work.

wait for monthy pythonesque telling….
shifters work by cable pulling rear mech right?…yes.
mechs dont have special brains they do what the shifter tells them too right?…goood.
the only difference is spacing and leverage ratio’s of mech but put remains different for the shifter…..we all follow? good class.
now people will stop talking about rear mechs with inconsistant cable pull.good.leverage yes.pull is constant but different shifter means less pull needed for the 10 cogs.
so it will work.
ok
Bruce hope it helps

Oops, yes, yes it should, and now is, so we can pretend that never happened!

Bruce that’s just confusing, it won’t work properly, and I’ve no idea if you’re saying that or not!

it will work is what i mean…cause the cable is pulled by the shifter thats all that changes,i dont why youd want 10spd mech with 9 speed stuff

IT WONT WORK PROPERLY

YOU CANT USE A SRAM MECH WITH SHIMANO SHIFTERS AND YOU CANT USE A 10 SPEED MECH WITH 9 SPEED SHIFTERS.

Almost there, it won’t work. Njee20 is right (except all Shimano road 10 speed is the same rear cable pull, it’s the front that is different on 7900, 6700 and 5700).

Just to reconfirm, you can’t mix Shimano 9 and 10 speed rear mechs and shifters.

Yep, you can run a new generation road rear mech on older shifters and vice versa. The things that are different are the front mech pull due to the wider chainring spacing and the brake cable pull.

i think what we have here is that shimano says NO but real world experience says YES
i’m gona sit on the fence as i run campagnolo shifters and 9 speed shimano cassette with a shiftmate!

Fair enough, good to know, thanks!

That’s only cross compatibility within 10 speed road stuff, 9 and 10 speed MTB stuff still isn’t interchangeable without some serious bodging!

Real world experience says no.

It won’t work.
If you express the ratio as mm of cable moved at the mech, 9sp @2:1 is 2×9= 18mm, 10sp @1.9:1 is 1.9×10= 19mm.
If 10sp shifted @1.8:1 (1.8×10= 18mm) the mech wouldn’t have to be changed.
If the leverage ratio varies as claimed, a 9sp chain wouldn’t work on 10sp cassettes because the sprocket spacing will narrow for the lower gears.
But I run 9sp chains on several 10sp equipped bikes because the wear rate on the 10sp OE chains is so poor (6 weeks, and there was an audible rumble from the drivetrain) and 10sp chains were difficult to obtain at the time, so I tried a PC951 they work perfectly.

I’m going to try a 10sp mech on a 9sp shifter out of curiosity now, just for the hell of it.
I’ll post back tomorrow once I’ve tried it.