Multcomedic

Looking for some help on my front derailleur. I have been having problems with overshifting the large cog and can't seem to get it tuned in. The outer adjustment screw is almost all the way in (clockwise) and the inner cog is aligned with out problems. I recently replaced the rear cassette and chain but this was a problem before the replacement. In the photo it looks like the chain is not aligning with the teeth and rolling off. Any help on a fix would be great.

Bill Kapaun

Is that a recent crank installed on the old BB?

Your pic looks like it's UNDER shifting.

Multcomedic

Same crank and BB. The chain rolls off to the outside (towards the pedal) when I shift from the inner chain ring onto the outer larger chain ring.

cny-bikeman

The pic that would be helpful is of the derailleur in relation to the chainring. In any case the front derailleur needs to be positioned correctly on the seat tube before adjustment - both height above chainwheel and rotation. See:
https://www.parktool.com/blog/repair-...ur-adjustments

Andrew R Stewart 

Some front der cages allow tweaking of the cage shape. The parts of the cage that extend forward from the cage's attachment point (to the parallelogram links) help guide the chain after the chain has begun to engage with the ring. Slight bending in of the outer plate tip can often act as a "catch' for the chain. We did this all the time BITD before highly shaped cages were the norm. A six inch crescent wrench is the preferred tool. Andy.

Multcomedic

Here are a couple of other angles of the derailleur. I haven't had any bashes or crashes to impact the cage so there's no reason for it to be bent. Could this be from worn chain rings? I've got around 3000+ miles on this set.

cny-bikeman

I don't see that worn chainwheels would be a likely cause. I see that the derailleur has been at least at the same height for some time. Have you checked the cage's alignment with the chainwheel per Park instructions? You can try rotating slightly counterclockwise to see if that reduces the intensity of the kick up to the large chainwheel while still allowing a crisp shift.

ursle

Is the crank arm correctly installed, it's placement is rather a part of the perceived problem, if it's on correctly and the chain won't ride on the large front chainwheel, as it's a new chain, the chainwheel needs replacing(3000 miles), aligning the front derailleur isn't difficult, tweaking it for excellent performance is also not a problem.

Multcomedic

More tinkering....It appears that the derailleur had spun a little around the seat tube and with some realigning and adjustment the shifting has improved. The chainrings also have some wear that may be part of the cause as well. Probably going to pick up some replacements in the near furture. Thanks for the help forum!

Sixty Fiver

Front chain rings should last more than 3000 miles... yours appear to be fine.

15,000 - 20,000 miles is a good expectation for the life of larger chain wheels while smaller chain wheels will wear out faster.