fadetoblack6902

This is on a nearly brand new 2005 Specialized sirrus elite with tiagra components.

When in the largest 1 or 2 cogs and the middle (sometimes large as well) chainring, the chain will jump off the chainring. If you pedal backwards, the chain will jump down up to 4 cogs and the chain will move off the upper jockey wheel and jam up.

All these symptoms seem to get better if you put too much tension on the front derailleur inner wire, but then the chain rubs on the outer front derailleur cage plate. The rear derailleur is set perfectly and shifts seamlessly in all other gears. It even shifts up to the largest cog perfect.

The front derailleur is set correctly (outer plate parallel to chain, a nickel's width above the large chainring, chain barely rubs inner cage plate when in middle ring/large cog combo.

There is absolutely no wear on the cassette, looks brand new. I can't find any stuck chain links, chain is clean and lubricated.

I am completely stumped. Any ideas?

Thanks,
Justin

Conveyor Belt

maybe your deraileur is bent a bit... have the LBS use a deraileur alignment tool on it to check it... just my $.02.

RussB

Try double checking the derailer set-up. I use the parktool website.

https://www.parktool.com/repair/

Just click on the bike halfway down the page. It takes you though all the checks, and can set up the bike right from the step of replacing the cable.