As per the title. Its for my son, the 1:1 of the sram changer would be an upgrade from the Shimano as its a big stretch for small hands and the thumbs only would be an improvement (I hope!). But would the indexing work or do I need a new rear mech? I know the front end works as that is what I run on my bike.

Paul.

SRAM do do specific ones that match the actuation of the Shimano mechs – I think they're the Attack and Rocket shifters – one of which is also available as a twist grip. I ran some Attack shifters that worked very nicely with an XT rear mech recently.

I don't know what would happen if you ran, say, an X9 or similar with a Shimano mech though.

Front yes, rear nay.