Chain jumping

Mrs_Ragbrutty

If there's an extensive explanation somewhere point me in the right direction. TY

I have a new chain on my bike. Now I have a problem that the chain is jumping when I ride it.

This happens when the bike is in the top 2 (smallest in size) gears on the rear in all 3 gears at the front.

By jumping I mean that the chain does not appear to be engaging the sprockets properly. This happens when riding but I can not replicate the problem when I'm not riding the bike. ie when I have the bike upside in the garage - pedling and changing gear.

Any ideas? Anyone know what is wrong and what I need to do to correct this? TY

Radioactiveman

I am guessing the drivetrain is quite well used.

Sounds like you may need to replace the cassette as well. Also iIf the chain is not releasing from the chainrings(chainsuck) you may need to repalce the chainrings as well

If in doubt get your LBS to check it

nyanza

New chain, but you don't mention your cassette? You need a new cassette (the cogs at the back), unless you have already changed it of course.

The gaps between the links in the old chain grew with use, and the teeth on your cassette wore down to fit those bigger gaps. You've now put a new chain with smaller gaps onto those worn cassette teeth and hey presto, you get a mis-match where the new chain and the original cassette don't mesh very well. Skipping's worse on the smaller teeth of the cassette becase there's less teeth over which to spread the pedalling load - You can't reproduce it in the garage because you aren't placing any significant load on the chain when the bike's upturned or in a stand.
This page shows you what is going on with your teeth with some pictures:

http://www.sheldonbrown.com/chains.html#wear

So, it's good practice to change a cassette everytime you replace a worn chain.

Mrs_Ragbrutty

Thank you. I shall try with replacing everything and see how it goes. It does make sense to me.
I did ask when buying the chain if I should replace anything else at rhe same time but was advised not to.

Having read the article on chain suck, I certainly recognise the symptoms from before I changed the chain. Didn't know it at the time but it's easy to join all the dots, with hindsight of course.

...and I thought motorcycles were complicated, can't help me with the Triumph can you?

acidstrato

have you tried fine tuning the cable tension at the barrel adjuster on the rear derailleur? before purchasing a new cassette give it a try with a 1/4 turn anti clockwise then if no change try turning it clockwise

Satans Budgie

Something as simple as a stiff link??????

Mrs_Ragbrutty

OK - I'm having problems locating the oe eqipment on the net.

Cassette: SRAM PG-950 9 speed 11-28
Rear Derailleur: Shimano 105 long cage

The bike is 2008, so is the above still readily available or will I have to use alternatives, if so what? Bit of a trek to a bike store, and they aren't open Sunday evening :-(

Aapje

Mrs_Ragbrutty wrote:

OK - I'm having problems locating the oe eqipment on the net.

Cassette: SRAM PG-950 9 speed 11-28

http://www.bike24.com/1.php?content=8;n ... id=0;pgc=0

Rear Derailleur: Shimano 105 long cage

Don't replace the derailleur unless you damaged it. It shouldn't have worn out (they can last decades). At most you might have to replace the jockey wheels, but they shouldn't have worn out yet. Just replace the cassette for now and see how it works.

nyanza

Second the derailleur suggestion. Keep it for now. They last for an age usually. Also, if you change only one thing at a time then you can locate what the problem is, as well as saving money.

Regarding it being a stiff link and the indexing being out - possible, but then again, you ought to be able to reporoduce those effects very easily when tinkering in the garage.

Mrs_Ragbrutty

Thank Aapje - never come across them before.

Really don't think it's a tight link at all, and have played with the indexing, yes I can get it very wrong in the garage. have tinkered myself to death, taken it to the extremes to see what happens, counted and marked til my fingers bled.

With the deraileur - the wheels seem to cost the same as a new derailleur on the net. Maybe bike shop will be cheaper I guess, no postage. The wheels don't look happy, I think I abused them a bit.

Thank you for your help.

desweller

Don't worry too much about the jockey wheels. If you're still at the stage of discovering that cassettes and chains wear as a set then your jockey wheels have years left in them!

If you're worried about them post a piccy and the Forum Elders will advise...

DW

NB As cassettes are so expensive, some people use two or three chains and rotate between them after a thousand miles or so to reduce the effects of matched wear.