wildcardcrow

i have a problem, my chain is slipping off of large lower derailleur cog before it gets to the smaller one (which puts it back inline) and before it reaches the cassette, i have stopped and set it correctly by hand several times it just slides off. my bike is still ride able but i am grinding my chain between the side of the derailleur cog and the mount.

i have recently changed my front cog set, the rear cassette, the rear derailleur and the chain. i don't know what is causing the problem, can anyone help me please

Metzinger

Welcome.
How's the alignment? A bent derailleur hanger can cause the chain to track poorly on the derailleur pulleys.
Can you show us a photo of the situation when the chain is derailed?

wildcardcrow

the alignment is fine, i have tried to upload pics but cant manage to attach properly

Metzinger

https://www.bikeforums.net/showthread...ictures-How-to

cny-bikeman

It's helpful if you pull up a diagram of a bike or part and use the correct terminology, and with any problem please tell us when it started and what may have changed just before that - equipment, fall, etc.

You are talking about the lower/idler pulley. Check first to make sure the pulley turns freely and has no damaged teeth or foreign material on it. Also make sure the pulley assembly itself is straight. If it's OK the derailleur hanger is bent inward OR the derailleur has been bent or twisted. Put the bike up in a stand and the drive train in a gear where the problem occurs. Sight from in back of the derailleur toward the chainwheels. The pulley cage should be parallel to the chainwheels and also parallel to the centerline of the bike (not pointing inward or outward).

I generally would not recommend that a lay person try to correct the problem. You could attempt to straighten the hanger when the derailleur itself is the problem and it's difficult to correctly align by eye.

DMF 

New Posters - please READ THIS

Correct terminology is crucial. I can't tell if you're talking about the front or the rear cogset. What bike is it? What year/model are the components? Since you replaced all this stuff, surely you know.




I know, I know. "Don't call me Shirley"...

wildcardcrow

the model is a 08 Raleigh AT10, bought new january 09 from a Raleigh dealer, ithe problem is the rear de-railer, and the bottom pulley. the cain refuses to stay on the teeth and slips to the outside of the cog, which then runs between the pulley and the mounting. the parts i have replaced are like for like

cny-bikeman

Follow the procedure I laid out above to see where the problem lies. Also need to know when the problem started, what changes or problems just before that.

DMF 

Sounds like the cage could be bent. No way to tell without seeing it.