I have 8 speed XT front and rear derailleurs with Alivio 8 X 3 Shifters on a bike I am putting together from spare parts I had lying around.
I have the rear derailleur working well, but I can't get the front to work properly.

I adjusted the derailleur so it is about 1.5 mm above the large chainring. I adjusted the low adjustment screw so the cage is just hitting the chain
when the chain is in the highest rear gear, then backed it off about 1mm. I tightened the cable by pulling the cable by hand, then using the adjuster
on the shifter, I took out all the slack.

The problem is when downshifting from the large chainring, it skips the middle chainring and goes right to the small ring. I have tried different cable
tensions, but to no avail. Can it be a incompatibility between the XT derailleurs and the Alivio shifters? Possibly a bad front shifter? I sprayed a little
WD40 inside the shifter body, but maybe it needs to be takes apart and properly cleaned and lubed?

Any ideas?



Thank you,
Ian

First thing to check is whether the front shifter is letting cable out in one length per click when you downshift or is it letting it all go at once? If you are not getting two distinct cable releases the trouble lies in the shifter. Can you get the derailleur to shift properly when you leave the shifter in the small ring position and pull the shift wire by hand? If so the derailleur is at least functional.

This was the problem. Actually, it's part of a two part problem.

I didn't notice, but because of a BB that is not the right size, (110mm), the derailleur was shifting to all 3 chainrings, but only using 2 clicks on the shifter.
When shifting into the large chainring, it would shift, but the shifter would stay in the second position. I hope the shifter isn't worn out.

I have other BBs so I will see if I have a 113mm BB and try that. Hopefully, the width difference will help.

Ian

Look closely to where the cable attaches to the derailleur. See a little tab there? The cable has to go OVER the tab.

Wow, great eye. I found that out when I was re-adjusting the cable. Everything works fine now, there were two problems,
Too narrow of a bottom bracket, had a 110mm, switched to a 113mm and the cable was not routed properly on the arm of the derailleur.

Geesh, I feel like such a noob.

Thanks for the help,
Ian

Here is what the bike looks like now that it is finished...

Trust me, you're not the first bike mechanic to have made that mistake.

That is how threads should look! Good job!