I had an FSA Vero triple chainset (30,39,50...paired with a Sora 9-speed transmission) and replaced the middle chainring with a 42 tooth ring. Now I sometimes get the chain not going all the way to the small ring when down-shifting. It works a lot of the time, bit sometimes, under load, it will rest between the rings and they will spin without engaging the chain. It doesn't jam, not enough room.

I'm thinking 2 possibilities:

1. New middle ring is incompatible (it had indents for the bolts, and upshifts fine, so don't think its on backwards.) It is labeled as a 10-speed ring.

2. Small ring got put back on backwards. When looking at it, the dish of the teeth take them father away from the middle ring. Is that correct? Flipping it would definitely bring them closer, bit if its wrong might make them too close...there are no markings on the small ring, or indents for bolts to inset...very plain.

Any help would be appreciated... Otherwise ill try flipping the small ring and see what happens.