Shifting problem

[roadie7]

A problem has developed when I'm in the biggest cog. As I'm climbing a hill, the chain slips into the next cog. I was wondering if anyone can suggest how to fix the problem before I take it to a mechanic.

Thanks.

[dustyrider]

Presumably it was shifting fine before? Cable tension or derailleur alignment would be what I'd check first.

[stien]

Would help to know what kind of shifting you're running, friction downtube suggestions will differ from integrated shifting.

[drewellison]

Could the derailleur hanger have been bent slightly? Or the cage?

Maybe an eighth-turn counter clockwise on the limit set screw would help.

[kingpin75s]

Presumably it was shifting fine before? Cable tension or derailleur alignment would be what I'd check first.

If it was previously shifting fine, your limit screw should be good.

Cable tension is likely it if you have not damaged the derailleur or hanger. Drop in to the small cog (big gear) and see if there is any excess slack to be removed.