I'm looking for possible/likely causes of an issue with my front chain-rings on my bike. It's a 3x8 setup and the problem is worst on the smallest front chain-ring, and worse again when combining smallest front chainring with smaller rear gears (so when chain tension is lowest).
What happens is below the chain-ring (the 'loose' side of the chain which is kept under tension by the derailler spring) the chain stays stuck to the chain ring (beyond the lowest 6-Oclock point where it would normally head off toward the derailler) - it then rides up and gets jammed into the frame. I commute on it, so its out in all weather and has a fine paste of road-muck all over it.
A few thoughts:
Maybe it's the spring in the derailler being too soft / gummed up not providing enough back tension (if I hold the derailler to act like a stiffer spring it fixes problem on the stand)
Maybe front chain rings so gummed up they're sticking to the chain and so holding onto it.
I have just put a new chain on it (cut to same number of links as the old one) - I normally get a shimano one but got a cheaper brand this time. Also it's a 9-speed chain on a 8-speed cassette which I know isn't ideal so maybe that's it (it happened once or twice before chain change but now happens all the time).
I can give it a good clean which might help if 1 or 2 is to blame - but any other thoughts?
Photos of 1st and 2nd chainrings linked below. The small chainring didn't look to bad to me (clearly I'm no expert) - the middle one looks worse yet has less chainsuck. Will try a thorough clean but if that chainring looks a lost cause let me know!