Hi

I have the Deore SLX groupo (11-34) on my 2010 Giant Anthem and I have this shifting problem I'm hoping someone can shed some light on.

When working the indexing from smallest physical cog on upwards (I'm on the middle chainring) - I get to the middle cog and it doesn't shift up anymore. If I tighten it a quarter turn, then it shifts up but I can hear the chain/cog out of alignment for all of the remaining cogs as I make my way to the largest physical. Strange!
If I turn it another quarter turn, then it jumps 2 cogs up!

This problem is happening after I've installed a new chain, cassette and chainring. I changed the cables about 2 months ago, so I would consider them relatively new.

Has anyone seen this before?

I'm not quite sure what you're adjusting by quarter turns (limit screw? barrel adjuster?), but I'd start the rear derailleur alignment process from scratch. You probably already know about the Park Tool website here: https://www.parktool.com/blog/repair-...nts-derailleur

It's also worth checking to make sure the derailleur hanger is properly aligned.

Ooops, sorry about that, I meant by quarter turns is the barrel adjuster on the shifters - I don't have one on the rear derailleur.

Checked the rear hanger, all straight.

Yup, went through that Parktool document; I gave more space to the limit screw (inside) and it seems to have helped. Not sure how the limit screw modification would affect a middle cog not shifting, though...?

If you haven't already, make sure the cassette is fully seated and that the cogs are evenly spaced and not bent.

I agree and all checked out okay.

You checked using a gauge? You didn't just eyeball the hanger?

Eyeball.

Actually just in case it is the hanger, i ordered 2 hangers and will replace to see what happens.

Your eyes might be better than mine. I suffer from astigmatism, and thus don't always trust my eyes when it comes to the straightness of things. I use a hanger-alignment gauge. FWIW, misaligned hangers are the #1 cause of shifting problems that I see. It doesn't take much of a bend at all to throw the shifting out of whack. Your bike's symptoms are classic for a bent hanger.

Careful - just because the hanger is new (unbent) doesn't mean it will be straight on the bike. They really need to be checked and adjusted with a tool. If you don't have a tool an LBS doesn't charge much to do it.

Thanks all for your feedback. I may just purchase a hanger alignment tool, save the drive back and forth to the Lbs in gas alone may be worth it.