My wife complained that her bike is giving her shifting problems. I put it on the stand. When I try to shift into the large chainring in front, the chain jams between the big ring and the derailleur cage. If I push hard it shifts, but it certainly isn't smooth. I haven't ridden it to see what it's like on the road, but it shouldn't be doing this on the stand, I don't think. I cleaned and oiled her chain to make sure it wasn't binding. I don't want to mess with the front derailleur - like changing the height or the rotation around the seat tube - until I know what I'm doing.
Is there a usual cause for this that I'm not aware of?
It's an old, rigid Specialized Rockhopper.