Have an otherwise great shifting, reasonably quiet SRAM Apex set up with one annoying foible: If I spin the pedals backwards the chain drops on to the BB shell. Can adjust adjust adjust the FD all day all night. . . External bearing BB, so I don't think it's that. Bent chain ring(s) maybe? Is there a tool or method to evaluate warped chain rings?
Or is there something else it could be?
Thanks, guys (and/or gals)