Hi all,
I have had the same XT crankset for about 3 years, and wasnt having any issues. At the weekend I changed the chain and cassette for new XT items, and since I cant get the gears to index properly.

I set it up perfectly from scratch and without load on the flat it is fine. However when its under load, the chain seems to catch, when I look down at the rear mech when its happening, every now and then it twitches the rear mech forward as if its grabbed something, but all the chain links are free. It seems to happen in either of the front rings that I use, and doesnt seem any better or worse in any cog on the rear cassette. Could it be the chainrings are worn, and the new chain is catching?

Any help appreciated!

Your chainrings sound like they're worn meaning they will be hooked. These hooks grab the chain causing suck. Replacing the chainrings will cure this.

I would always change the front rings with chain and rear cassette,If the teeth are well worn on alloy sprockets it wont mesh properly with the new chain.

try pulling the chain off the teeth at the 9 oclock position,(middle ring)if the chain clears the teeth the chain rings are goosed.

also check for loose chainring bolts,a chipped or bent tooth,or slight warping when turned. hth 😉

chain rings is my prognosis too

My Xt crack and cassette do the same, Its got to the point now that I just stick cheap chains and cassettes on and when it starts to play up BANG new one goes on then it stops ya gotta save that carbon frame 😯

Deore inner and middle chainrings are needed if on tight budget to fix.

Cheers guys, will try the "pulling the chain off at 9 oclock" thing. But will just get a couple of new chain rings anyway as I think its probably well overdue!

Another thing I cant understand, When I got the bike initially, I was able to use all three chainrings, and get full range on all the cassette cogs, but the bike got stolen and returned to me, and needed a new chain and front mech. I got the bike back and since then have never been able to get onto the big chainring. Ive changed the chain once before to try and sort the length out, but if its loose enough to get onto the big ring, at the lowest gear, ring combo, its hanging loose. Cant understand it. Cant even remember if they changed the rear mech after it was stolen, I suppose if they did and fitted a short cage as opposed to a long cage, that would cause the problem?

Yup 3 years = prob change the whole lot. YOu may find the chain starts to jump of the rear cassette.

Sounds like the front mech needs re-indexing.

How are the jockey wheels on your rear mech? If they're the same age as the rest of the chainset then they're likely to be pretty badly worn and can slacken the chain off quite a bit more than you'd think.