Originally Posted by
Mondoman
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:
http://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...?