Chain catching pulls up derailleur
 

My problem is that on the smallest chain ring (front), something is catching the chain and pulling the derailleur arm up. Its scary and I am afraid to stay in low gears.
I am not sure whats going on. At first I thought it was my crappy derailleur, now that is replaced. New chain as well, new rear cassette too!

So I found spurs in the teeth of the front chain ring. i got a file and filed them smooth. Its still happening.

Anyone?

Dave

Look closely at the teeth on your chain ring. Are they starting to wear and even slightly resemble hooks or backward shark fins with the front (loaded side) of the teeth becoming concave? If so replace the chainring and the chain too if you've put any miles at all on it.

Another thing to look for would be teeth on the chainring that are bent to the side which would cause the chain to not release from the chainring.

Chain suck sucks, and can be fatal to a deraileur.

Well, I suppose I could replace the small chain ring. Its a new derailleur and new chain and new rear cassette.

Dave

you may have damaged the chain though as a result of the chain suck.

Well, I haven't done much riding since the overhaul. For now, I'll just keep my ass out of the low gear ring. Maybe I'll take it apart again and do some more filing. I should have just bought a new ring today, but now the bike shop is closed and I gotta catch a ferry at 7:30am tomorrow. Thats how it goes! Eh, it'll work out. I just don't want to trash any of my new crap I just put on.

Dave

Is it possible that chainring is warped? narrows down
and pulls chain off rings an upward to next ring?
Am I way off base here?

Marty

It sounds like you might have a tight link in the chain. The smaller gears require the chain to move more than the larger ones and a stuck link would be a bear to pull through the pulleys on your rear derailleur.

If it's a new chain the mechanic could have pinched the link when he/she put the new chain on.

Boo! Hiss! Don't start replacing things until you've identified the source of the problem!

For information on both 1-ring and 2-ring suck, see
Chain-Suck in a NUTSHELL for :
- causes and mechanisms
- how to avoid and remedy
http://www.fagan.co.za/Bikes/Csuck/chain-tri-icn2.gif

I looked through the site. I think it may be a case of the shark fin catching on the chain since I've filed down the spurs on the ring. I was a bit hesitant to take the file to the teeth too much but maybe thats my only choice until I get to another bike shop. Probably will be there in another couple days tho. And I believe I will have to replace the ring, but we'll see.

Dave

Well, I solved the problem a while back. It turned out that when I took off the small chain ring, I put it back on reversed. This is why there was chain sucking. So, just when I was about to purchase a new small ring, I ask the guy if the one I had was on correctly and he said no, so I told him I'd flip it around and see if it made a difference before buying a new one. Viola!

So, I think someone in the replies said something about locating the problem before replacing stuff.
That was great advice, Thanks..

And thanks for all the other help out there.

Dave