guitarjack

Hi,

I just bought a bike from a guy and it has this issue where whenever i put pressure on the pedals, they lurch forward, so i have to try to be as light as possible, but it's a major pain. I was wondering if it sounds like a problem with the cassette, or if it could be that it needs a new chain or what. Thanks,

Jack

Metzinger

Could be cassette, chain, chainrings etc.
Sheldon Brown has a useful site with loads of info and repair instructions.
Look at this page.

guitarjack

I replaced the chain but that didn't do anything. I checked that website but their skipping section only talked about when shifting gears or if the chain was worn, which it couldn't be either of those, because i don't shift gears and it still happens.

DOS

New rings and/or casette

jco1385

is the freewheel/hub spinning freely (as in the pawls arent engaging)? or is the chain skipping over the teeth on the cog/chainring? are the teeth on the cog worn?

Panthers007

If it's a bike that has seen lots of use in the past, and has a new chain that's skipping, the best bet is the old cassette needs replacing too.

guitarjack

So I took the bike back to the guy who sold it to me, and we put a different rim on it with a slightly larger cassette and slightly smaller teeth, and the problem was fixed. He was saying that the chain may have been fitted for a different size cassette. Does that explanation make sense? also, do I have to adjust the rear derailleur at all because it is a different cassette?

Thanks for all your help,

jack

DOS

More likely the second casette is less worn the original one.

As for adjustments, if all that is different is the casette, then adjustments should be minimal. No two casettes are exactly the same so I always find when swapping out that I need to mike slight cable tension adjustments, but nothing more than that. However, if the new wheel has a completely different hub, then more significant adjustments may be becessary. For example, I have rear wheels built on both 9 speed and 10 speed ultegra hubs. While both have identical 9 speed SRAM casettes, when swapping out the wheels, I have to tinker just a bit with limit screws to adjust for different hubs.

simplify

no.

yes. And, for tuning your derailleur adjustment if needed, here's a great step-by-step: https://www.parktool.com/repair/readhowto.asp?id=64

Cadfael

It may not be your issue, but I have just solved the same problem by fitting new jockey wheels in my RD. I had done everything else, checked chain wear, sprocket ware, pawl bearings in the rear cluster, shifter setting... etc etc.

It may not be why your chain is slipping, but it is worth a look at. My old jockey wheels looked like a sheriff's badge when I took them out they were that worn.

guitarjack

Ok thanks guys, you've been a big help and a great source of wisdom!

jack