Shimano XTR - Shifting Problem

[timnoyce]

On my mountain bike I am running an all Shimano 3x9 setup consisting of a mix of Deore triple chainset, XT Shifters, XT Front mech and an XTR M971 rear mech.

There is an indexing issue with the rear mech as it loses its way about half way up the cassette. My father in law used to own a bike shop so knows his way around a bike, but even so it has got him a bit flumoxed. So far we have checked the alignment of the mech hanger (seemed good), changed the gear inner, adjusted the length of the gear outer to give a nice big loop at the back, swapped out the XT shifter with an old deore one and it is still not right. Starting at the bottom of the cassette, it shifts crisply with one change per click till about half way up (so no issue with cable tension or adjustment screws) where it loses its way and will either not shift, takes ages to shift, or requires a double click to get it to go. The same happens if you start at the top of the cassette and change down the other way. Fine to start with, then something goes out of sync.

Anyone got any ideas? Having replaced the cable and the shifter we have to assume it is the mech. Doesn't seem to be any damage on the mech and it all moves freely. I wouldn't have thought that the mech would cause a indexing issue as assumed that that is defined by the cable pull from the shifter. So either the mech is goosed, or I have a pair of dodgy right hand shifters (which seems unlikely).

[richardxjr]

Cassette properly spaced? Otherwise mech hanger I reckon.

[timnoyce]

Mech hanger has been checked with a mech hanger tool, and I have tried different wheels with a different cassette. Still the problem is there!

[The Walrus]

Can be the mech spring has gone got crap stuck in it, sounds like you have tried every thing but changing the rear mech ?

Worth a try especially as Merlin have them at £30.00 odd quid at the mo

[vwsurfbum]

you sure the XTR mech is 9 speed?
try a different mech.

[SkinnyBoy]

I had a similar problem with a 10 speed SLX mech and 9 speed XTR shifters. Swapped out the shifter for a 10 speed XT and all was well. I think the swing ratio is different for 10 speed.

[timnoyce]

Correct. I have not tried changing the rear mech as that is one thing I do not have any spares of. I'll try and take it apart and give it a clean tonight and see where I am after that. It is defs all 9 speed componentry.

[AlasdairMc]

Mech is twisted. Check the alignment of the cage relative to the cassette as it moves up and down. It's easier to do this with the chain off if possible.

[deadtom]

how old is the cassette and chain? could be the shift ramps are past it

SkinnyBoy said:

I had a similar problem with a 10 speed SLX mech and 9 speed XTR shifters. Swapped out the shifter for a 10 speed XT and all was well. I think the swing ratio is different for 10 speed.

were you using a 10 speed cassette or 9 speed?

[SkinnyBoy]

I Was using a 10spd SLX mech, brand new 9spd SLX cassette and chain and my existing 9spd XTR shifters. Whatever I tried I just couldn't get it to shift properly. Put a 10spd cassette and chain and Xt shifters on and it worked perfectly. 7/8/9 seem to work together, it's the mech swing ratio on 10 speed combined with the cassette spacing which excludes using the mech on a lower number ratio cassette. I thought this sucked as the old 970 shifters are a work of art.

[deadtom]

SkinnyBoy said:

7/8/9 seem to work together, it's the mech swing ratio on 10 speed combined with the cassette spacing which excludes using the mech on a lower number ratio cassette.

yup, they changed the pull ratio on the mech. the earlier stuff was called hyperglide, but with 10 speed they started calling it dynasis (or dynasys?), and it isn't backwards compatible

[markoc]

Have you used new cable outer? I had a similar issue and it was that the metal "shielding" in the outer was crimped slightly which meant the cable wasn't passing through cleanly. Couldn't see it on the bike, but once off the bike it was clear. It was preventing the cable sliding back under the spring tension - pissed me off as I'd assumed rear mech (which was due a change) and bought a new one. with the obligatory upgrade from what was there in the first place.