Hi. I’m currently running a 1×9 setup with 9 speed cassette and shifter and a 9 speed Saint RD.

If I move to a 10 speed cassette, chain and shifter, will the RD work with this setup, or do I need a new RD too?

The max on the RD is supposed to be 34T but it seems like it’ll work with a 36T. I can’t imagine why it wouldn’t work with a 10 speed cassette and shifter – the pulleys will be the same width, won’t they? Or am I having a failure of imagination.

I like my short cage mech and I’d rather not wait for the 10 speed Saint RD to appear.

new derailleur needed. Pull ratios of 9 and 10 speed RDs are different apparently.

Fair enough. I always thought that the amount of cable pulled through on each click was determined by the shifter, not the derailleur? And that the derailleur is dumb in that respect – it’s just a spring.

Give it a go.

My mate is currently running a SRAM derailleur with SLX shifters, and it more or less works, bar the lowest cog or two.

Yep, probably I’ll just get a chain, shifter and cassette and if it doesn’t work, then I’ll spring for a mech as well.

If anyone knows if it’ll definitely work or not work, I’d be glad to know.

Cheers.

Well, thinkign about it – if a casette is 50mm wide (say), the cogs on a 10speed are 5mm apart. whereas the 9sp ones are 5.5mm – so a click of a 10sp shifter moves the derailleur slightly less – bu the end of the block, you could be 4mm out of line – might miss a few gears.

You’re describing what will happen if you use a 10 speed shifter with a 9 speed cassette. If a 10 speed shifter moves the derailleur slightly less, that’s fine because the 10 speed cassette is spaced together more closely.

The derailleur just moves the distance specified by the shifter.

I’m sure it won’t work as the rear mech angles are set to match the number of gears. The rear mech is not dumb as you say but is built to match the 10 speed shifter.

I’m sure if you do a search on here you will fine a few threads about how it won’t work and the reasons why.

recipher – Member
You’re describing what will happen if you use a 10 speed shifter with a 9 speed cassette. If a 10 speed shifter moves the derailleur slightly less, that’s fine because the 10 speed cassette is spaced together more closely.

The derailleur just moves the distance specified by the shifter.

I misread you, thought you were still using the old shifter too.

It’ll sort of work then, but as someone said, the cable pull was changed on the 10sp – they pull more cable, closer to the 1:1 SRAM ratio, so it’ll probably go out of whack towards the end of the block even more so.