Derailieur confusion

HixX

I was toying with fitting XTR derailieurs and shifters but I'm confused. How do the Shimano model numbers work? I assumed that M970=XTR but I also find M972, whats the difference?
How do I tell if I need a "long cage" or medium
My bike currently runs XT, so all that should be required are mechs and shifters, the chain and cassette should work together, right?
Finally, are XTR that much better than XT?

Sorry for the questions

supersonic

There is a big post on Shimano codes somewhere. Basically the 950 and above numbers are for XTR - the higher the number, the later the model, while some digits refer to model type ie rapid rise.

XTR is lighter and smoother than XT, and should last longer. My M950 from the last decade is still as snappy as when new!

Anonymous

i think you can run xtr mechs with any shimano shifter. (but i might be wrong)

supersonic

Yes, the mechs work with any shimano shifter (or named SRAM) - rapid rise of course changes the spring orientation

Cage length depends on what combo of cassette and chainrings you are using, ie the chain capacity. Usually long cage for 3 chainrings. Look up derailleur capacity.

HixX

Thanks guys.
What do you mean by "rapid rise of course changes the spring orientation"?

supersonic

The spring pulls the mech to the smallest gear, (or largest cog). So in effect it reverses the way the shifters operate. Has some benefits, and shortfalls. All down to preference.