[Optimus]

When shifting from large chainring, to small chainring, 50/34, the rollers on the chain land right on top of the teeth of the chainring, which sometimes causes the chain to fall off on the inside. The limit screws are set correctly, but makes no difference. The chain has some miles on it, but not to the point of replacement, a very slight stretch, under 1/16. The chainrings are in decent shape as well, used, but not overly worn.

Any thoughts?

 

[TrojanHorse]

Chaincatcher.

16 teeth difference is hard to handle for some drive trains, although I'm a little confused by your statement that the rollers land on top of the teeth but there's no chain wear.

I'd go check mine but the chains in a tub of solvent at the moment. :smile5:

 

[MrMook]

Chaincatcher.

.....I'm a little confused by your statement that the rollers land on top of the teeth but there's no chain wear.

The rollers (bushings around the pin) are landing on the "peaks" of the chainring teeth, rather than the "valleys" between the teeth, hence the chainsuck.

I also think it's a result of size of the jump between chainrings....if you think about the distance the chain has to travel in a linear direction when being pulled off the large chainring, it may, mathematically, align the rollers with the teeth in just such a way that they land on top until the rest of the chain has a chance to come off the big ring completely.

 

[JimP]

This can be caused by the small ring not aligned properly with the big ring. The big ring has a pin that should be behind the crank arm to prevent the chain from becoming stuck there if it is shifted past the big ring. The small ring from most manufacturers has a "V" or arrow indicating the crank position. I have a small ring on one bike that doesn't have any indication where the crank should be. When I first installed it, the shifts to the small ring were very rough and sometimes acted like the OP describes. I reinstalled the small ring, rotating it one hole (1/5 revolution) which seems to have solved the poor shifting issue.

 

[forge55b]

I'm going with JimP on this one. Depending on what chainrings you have, it should have an indicator for the correct orientation. And the "V" arrow from what I can remember is a notch on the inner circle of the ring and it goes inline with the crank.