Probably done to death but all I can find is people discussing Shimano (which is easy to understand) or coming up with information about shimano when asked about sram (Shimano 9spd is 2:1, 10spd is 1.9(ish)), but Sram is 1:1

So if both Sram 9 and 10 speed are both 1:1 (cable moves 1 unit the jockey wheel moves sideways buy 1 unit) how are they incompatible? Just wondering as I have components for both which are of various quality and wondered about mix and matching to get the better components?

Cos none of them are really 1:1 (Shimano claim their 10-spd is this). One might be 1.5:1 and another will be 1.1:1, and so on. It might almost work, but never 100%.

So if both Sram 9 and 10 speed are both 1:1 (cable moves 1 unit the jockey wheel moves sideways buy 1 unit) how are they incompatible?

i guess it could not be the same ‘1’ to the same ‘1’ maybe?
ie 9spd could be 7mm move to 7mm cable and 10spd 6mm to 6mm.
just guessing. don’t aktchly know

jamiesilo is right, in essence the mech has unrestricted movement across a wide range, its the shifters on the bar which control the movement across the cassette, so cassette and shifter need to be compatible, not withstanding some hi-tec new mechs are intolerant of mix and match use.

No, SRAM 9s was 1:1, Sram 10s is slightly less than 1:1, shimano 9s was 1:2, shimano 10s is slightly less than 1:1.

Apparenly some XC racer have been running 10s SRAM shifter (gripshift specificaly) with Shimano 10 mechs as the ratio’s are close enough.

No, SRAM 9s was 1:1, Sram 10s is slightly less than 1:1, shimano 9s was 1:2, shimano 10s is slightly less than 1:1.

Apparenly some XC racer have been running 10s SRAM shifter (gripshift specificaly) with Shimano 10 mechs as the ratio’s are close enough.

This.

The Jameses are confuddled, I think, can’t really work it out!

CBA to get into this now, some work together by happy coincidence others never will.

So just follow TINAS’s guidance and you won’t go wrong.

Although I’d take the ‘SRAM 10 speed shifter/Shimano 10 speed mech’ combo with a pinch of salt!