chain jumping

welshkev

i've just put a new chain onto my bike after my old one snapped, i measured it against the old one and then fitted it and it all seemed fine. i went for a ride yesterday and when it's on the front middle cog and biggest back cog it jumps down onto the smallest chain ring on the front. is this just that the chain is too long?

ride_whenever

no, it's an indexing thing

Sheptastic

or a worn cassette. Should really change the cassette if you change the chain.

ride_whenever

No you shouldn't. If you replace your chain inside 0.75% wear then you can get 2-3 chains to a cassette.

Considering you've snapped the old one, your cassette and rings quite possibly are shagged, check for shark-finning. But from the sounds of things your indexing is a little out, Check chain length by running the chain round both large rings without going through the mechs, then add one complete link (one set of inner plates, one set of outer plates)

welshkev

the cassette is the back yeah? so that shouldn't jump it on the chainset up front should it?

i'll try checking it around the cogs, cheers for that

The Rookie

It sounds like the front mech needs checking (indexing) it won't be a worn cassette and I doubt its a worn front either...

When I put my bike on the road it was fine, after oiling the chain (it hadn't been oiled for a good long while from before when I got it and then built it up) the front mech needed adjusting (and shifting was better/easier) so it wouldn't surprise me for a new chain to need the indexing 'tweaking', the new chain will be stiffer (against sideways bending) for example.

Simon

stumpyjon

It does sound more like an indexing problem rather than sprocket wear although it often shows up after changing chains. You usually know you've got worn sprockets on the front as you start getting really bad chain suck.

welshkev

cheers for all the replies guys, i've tweaked the front mech and touch wood, it all seems fine.

Thanks again