So, I bought a brand new Zee mech a while back and ran in on my CX bike with an 11/36 XT cassette with no problems for months. I took it off and tried fitting to my sons Orbea a few months ago with the same cassette but for some reason it wouldn’t take the slack up in bottom gear. I resigned it to the spares bin until the other day when I fitted it to my Rockhopper on yet again the same cassette and this time it takes up the slack but catches the top sprocket when you change into first. Any suggestions?

It’s too short a cage to handle chain growth plus an 11-36 cassette (works fine on my hardtail, didn’t work on my full-sus). I think you need to adjust the B screw to move it away from the sprockets on your Rockhopper.

It just needs setting up correctly. B screw, high-low limit screws, chain length.

Is it the free ride or DH version. Different mech capacity.

I’ve got the FR version running on an 11-42 cassette on a full sus. About 800 miles now on that setup.

If it wasn’t taking up the slack, is the spring knackered.

I had this with a zee mech (short cage) a while back, given to me by a mate who bust my xt one. Tried to fit it to a 30t NW/36t cassette, wouldn’t take up slack no matter how I fiddled. Then fitted it to a different bike with the same gear ratios and it worked fine. It’s stayed on that bike since

Probably nothing wrong with the mech but different lengths between BB centre to axle.

If it ran ok on one bike, putting it on another with different length chain stays may be the cause of the problem.

Maybe the chain needs shortening / lengthening

Had the same problem with a Zee when I fitted it to my hardtail shortened the chain to compensate before realising there was a screw to adjust it.

Turns out there was also one on the XT much I took off but I had never needed to adjust it so didn’t twig what it was for.

Also is the pin definatley sitting on the hook on the mech hanger/frame?