That's not likely an adjustment issue, but we need to know what the rear derailleur and shifters are and if you have tried adjusting the cable tension. Also, what is your typical cadence (crank rpms) when this occurs and on which chainrings does it occur? Finally, I am assuming you did not have the problem previously, correct?.
Last edited by cny-bikeman; 08-05-14 at 01:08 PM.