Another chain skipper!

[jak_jtb]

Hi Guys, as i couldn't find my exact situation i thought i'd best post up.

i recently replaced my chain and have since been having a right nightmare when riding as it keeps jumping forward on every downstroke.

the chain isn't skipping gears or anything it is just lurching forward, i have checked for loose cranks, bottom bracket etc and they are all fine. when trying to diagnose the problem thou it is very difficult as the problem only appears under load. when i was testing it out thou i could look down and see that the rear derailleur lowest jockey wheel was pulling forward 2-3 inches and then suddenly jerking back and this was what was causing my chain to skip and making the bike unridable really. i commute 30 miles every day.

i rang evans cycles and spoke to the bloke there who said it was because i hadn't replaced my rear cassette at the same time as replacing the chain but i doubt it is the cassette as that was working perfectly fine with my old chain...

any ideas guys as I'm properly stumped here....

[DaveM]

Chains and cassettes tend to wear into each other and it is quite common to get skipping after replacing one and not the other as the cog teeth and chain don't line up anymore. This isn't the only possible reason, but it is very common. I suspect the jockey wheel movement is being caused by the chain slipping and not the other way around.

[nfmisso]

Dave is correct