I continue to fight the drivetrain on my Trek 4300. Last Fall I put a 9 spd crankset on my 8 speed set up and it seems like ever since then i have had trouble. I'm almost to the point where I am going to get a diffferent bike, because I can't figure it out.

It was less than a year ago that i put on the crankset. Since then, I have replaced 3 chains. (today i did the 3rd.) I've replaced two cassettes. (today is the second) The mileage since then is around 3000 miles on mainly dirt and gravel.

Today I replaced the chain and cassette, like i said. All is well except I feel a grinding sensation in my feet when I have the chain on the middle ring. Also, the jockey pulleys seem to hop back and forth. This ONLY happens in the middle ring on the crankset. This also happens to be the ring I use 90% of the time. When i run on outer or inner on the triple crankset, everything seems fine.

Also in the stand the chain runs smoothly on all rings, forward and back. I am certain i don't have a stiff link or anything like that. Looking at the rings, it looks like the middle ring's teeth are more pointy than the others. I can only surmise that the new cassette, new chain and the worn middle ring "don't like each other."

Do these sound like the symptoms of a worn chain ring? Thanks for any help! I don't want to put my horse down, since she was my first. We are approaching 10,000 miles together and it would be a sad day.

EDIT> I just went and looked a little more. I noted that with both tires on the ground when i try and push forward on a crankarm, there is about a 1-2mm area of slack before the chain engages the chain ring teeth, on the middle ring.

This doesn't happen on the outer and inner rings.

Click here for video.

How old is the chain? Your problems sound more like a badly worn chain than anything else.

About 3 hours old. I'm pretty certain it is the chainring. https://media.putfile.com/slip-86 (sorry for jumpy video-hard to film and pedal at same time. Watch how the chain slips on the cogs. Not normal is it?

Does anyone concur with my diagnosis?

after 10000 miles, id have long since replaced my chainrings... their is no point changing cassettes and chains if theyre going to be used on worn chainrings...

the problem is obviously the middle chainring... change it.

Errrr, the middle chainring has about 3000 miles on it. Still I think it is worn out. This is my first crankset with aluminum rings. Guess they don't last very long.

Dirt and gravel are hard on components. Lots of dust to grind away parts. Perhaps you should revisit your cleaning schedule.