Bicycle Mechanics - New chain gets thrown off

The day before last Sunday's century ride I decided that it was time to replace my chain. I replaced the Campy C9 chain with a new C9 with the same number of links. Before replacing the chain I never experienced the chain being thrown off outside the large chainring. On the ride it happened 3 times.

I did not adjust either of the derailleurs; I just replaced the chain.

Any ideas on why this started to happen?

SteveE

Check the limit screw on the front der.

OK, but my real question is why a new chain should do this.

It should not. The chain has nothing to do with it derailling, it is the der. itself that is derailling the chain. Unless you have bent teeth on the chainring or a bent chainring.

Transplant rejection, the new chain and wornchainrings don't mate to each other to good and the chain is riding up and off. When you had the old chain on there it fit the chain ring well enough that minor overshift did not affect it. Tweaking the high screw just a touch might stop it if you have no other problems like skipping.

I think it's kind of strange because I didn't touch the derailleur between the time I took off the old chain and put on the new one. I guess I'll set limit screw and hope the problem goes away. Neither the teeth nor the chainrings are bent. The cranks are Campy Racing-T and are less than one year old.

Since you made no other change, you have to look at the one change made, the new chain and its different fit, compared to the old chain, to the chainring.

What Chuck said ;)