jambon

Hi

I replaced a very worn out chain that had snapped on a neighbours bike using a new 9 speed sram pc951 chain . There is an issue now where the rear deraileur pulls forward under load and the chain gets wrapped around itself on the front ring .

On looking at the lower jockey wheel on the Rd I see that it is extremely shark toothed compared to the the upper pulley .My imagining is that the bike has been ridden with a very worn chain for so long that the jockey wheel is wasted . It ran ok with the old chain because the old chain was stretched out to match its worn state but now the new chain does not match it and is falling off it and getting trapped pulling the rear mech forward .

Is my thinking correct ?or could there be another reason for the rear derailleur to pull forward and for the chain to get stuck ?. My neighbor argues that the chain must be the wrong type but I matched the old chain for length and gearing (9 speed ) . To my knowledge there is no difference between a 9 speed road chain or mtb chain (this bike is a mtb) so a sram pc951 should work ,

Thanks in advance ,

J

trailangel

"rear deraileur pulls forward under load and the chain gets wrapped around itself on the front ring "
Chain suck. Google it. Worn out front chainring.

chorlton

You may need to look at the state of wear on the front and rear cogs as well. One thought... When you say it is wrapping on the front ring I would guess that it is wrapping from the bottom in order to pull the dérailleur forward. Assuming the front rings are still usable you may have a stiff/misaligned link in the chain... the one you joined the chain back together with[?].

jambon

Thanks for the responses folks

On looking at the smaller of the double front rings it is very worn / shark toothed looking . I expect that is worn too .

Checked chain for a stiff link but found non , I had connected it up with a power link which seems fine .

eveything about this bike suggests neglect , the grips , the brake pads , the loose bottom bracket and worn tires .

As I said above could the bike have seemed to run fine in its worn state but once a fresh unworn part was introduced ( chain ) then this part would not have played well with the other worn parts ?

trailangel

"As I said above could the bike have seemed to run fine in its worn state but once a fresh unworn part was introduced ( chain ) then this part would not have played well with the other worn parts ?"
Yes. Now you probably have to replace the cassette, front rings and the rear derailleur/or wheels.