Gears jerking when under pressure

mcowan77

Just installed new front mech, crankset, bottom bracket, chain and rear mech
Shimano sora triple

All gears tuned and indexing fine when on work stand

But when out on bike and under pressure I'm getting a jerking/ crunching noise and when in middle and granny ring....big ring ok

This happens with every rotation....the chain isn't jumping but it feelslike it ( hope that makes sense)

Ay ideas what it could be?

Cheers

mcowan77

I didnt replace the cassette... Could this be the problem?

k-dog

Yep, a mismatched chain and cassette is the usual culprit for that - while you've changed everything else it would be a good idea to do the cassette anyway - it will give you a brand new drivetrain really.

mcowan77

Put the old chain on its working fine...new cassette ordered

Do u need to change cassette every time u put on a new chain?

k-dog

Sort of. They wear out together - but if you change the chain earlier you can get 3 or so chains to a cassette. If you leave them too long then a new chain won't mesh with the old cassette as they're too different.

You can get measuring tools (or just use a ruler) and there are guidelines for changing the chain and then when you have to change both.

keef66

This ^

I check my chains regularly and replace them at 0.75% wear. 10 speed chain on a triple and they seem to wear relatively quickly despite cleaning and lubing regularly. The upside is that I'm still on the original cassette after 4k miles.

The alternative is to run chain and cassette to destruction, but that can mean you'd also need to replace the chainrings, making it an expensive strategy.

laurentian

When I recently replaced my cassette and chain, I experienced two problems on the road that were not apparent on the stand. The second of these was remedied with the help of our learned friend Keef.

The first one was similar to yours. As I was completely new to this I had made the mistake of not doing up the cassette holding ring tight enough causing the cassette to slip. I simply tightened it up (using the shimano cassette tool) - first time I was a bit nervous to do this as it clicks when the "teeth" on the inside of the holding ring rotate against those on the cassette. Don't know if this is useful but might be worth a try.

laurentian

Ignore that! just re-read the original post - apologies

mcowan77

It's still doing it with the old chain and cassette ...it thus because its a new chainring?

k-dog

Could be. More likely to just be past it so nothing will work well.

desweller

As a rule, chains and cassettes wear out quickest. Since the innovation of outboard BB bearings ( :roll: ), BBs come in at third place followed by chainrings, rear mechs and finally front mechs.

ricky1980

did you install the correct chain length onto your current setup?

also when you say the gear indexed fine, are you 100% sure? sometimes when you installed new mech at the back, there is that tiny bit of slack in the cable that will only be taken up on load as opposed to being on stand. so you may think it is all correctly indexed but there will be slight out once you have put some force down.

personally i don't think the problem is your cassette and chain mix as it should happen on all gears (i am assuming you use all the cogs), unless your cassette is badly worn on the middle ones and granny ones only.

also I hate sora shifters they are bad!

mcowan77

Thanks for the help

I cut the chain to the same size as the old 1....the chainset although a different make fsa to shimano is the same size....would i need to shorten the chain

desweller

ricky1980 wrote:

did you install the correct chain length onto your current setup?

also when you say the gear indexed fine, are you 100% sure? sometimes when you installed new mech at the back, there is that tiny bit of slack in the cable that will only be taken up on load as opposed to being on stand. so you may think it is all correctly indexed but there will be slight out once you have put some force down.

personally i don't think the problem is your cassette and chain mix as it should happen on all gears (i am assuming you use all the cogs), unless your cassette is badly worn on the middle ones and granny ones only.

also I hate sora shifters they are bad!

Faulty reasoning. Most people will use 2 or 3 gears very heavily.

Ref. chain length: Read this to find out how to set your chain length.

mcowan77

Gave up took if to lbs.... Chain was 2 short... Its now moving great

I cut the chain to the same size as the old 1.

Confused!!

Its

smoggysteve

The whole chain and cassette wearing out together is a fallacy. If your chain is old and stretched and not looked after, cleaned oiled etc then it will prematurely wear out the cassette. If you look after your chainset the cassette will outlive the chain many times over.

ricky1980

indeed steve, on my old allez, the cassette chew thru 2 chains that's over 3k on each chain before needing replacement.