Jumping Chain

daviesee

I have just replaced a broken chain and fine tuned my derailleurs after cleaning.
Everything is running sweet as a nut - until I get on the bike :evil:

As soon as I put any load on the pedals above gently spinning, the chain jumps 3 or 4 times per revolution. This happens in any gear and I stress that it is not trying to change gear, just jumping forward a wee bit. I would not like to do a hill climb :x
I have slowly rotated the cranks and watched every link go over every cog and it is very smooth.

I am at a loss. Anybody got any ideas?

bikeit65

Silly question but do you have the new chain the right length?

daviesee

At this stage there is no such thing as a silly question.

Yes. I followed the instructions to the letter and even practiced breaking and making on the old chain first.
Everything looks perfect but it can't be :?

bikeit65

same amount of links on each

JamieRa

i had the same problem recently when i replaced a snapped chain.
it turns out the cassette was worn. i replaced the cassette and it is running normal now.
apparently when you replace a chain you should replace the cassette too, or vise versa...

bikeit65

you are correct but it depends on how old the parts are, how old are the parts? it is good practice to replace chain and cassettes together as the wear away at the same rate.

daviesee

Since a picture tells a thousand words.......



Smallest cogs as per instructions



Instructions



Moved to the big cog at the back to show the range.[/img]

Looking at the top photo the derailleur may be a bit too far back. Maybe I could lose a few links. Opinions? Campagnolo Centaur if that makes any difference.
Once I take out links, I don't have the over-priced tool to put links back in. I have used a Wipperman quick link as this is the only way I can see to repair a Campag chain on the road. If it jumped on the quick link that would make sense but it jumps too often. :?

windup

When I had a jumping chain it was due to worn chainrings - it also behaved well in the stand and I had just replaced the chain. Try spinning the cranks on the workstand with the brake held to give some torque.

daviesee

Bikeit65 wrote:

you are correct but it depends on how old the parts are, how old are the parts? it is good practice to replace chain and cassettes together as the wear away at the same rate.

Less than 3 years and @ 10k miles. It is the first time in over 40 years of cycling I have had a chain problem but from reading here, I suspected that may come up.

If it was only a few cogs I would have concluded it was the cassette as well but prior to the chain break I had no issues and it happens equally on every cog but if that is the consensus....

I may be ordering a new cassette tomorrow.

bikeit65

I too had this problem ,replaced the chain then the rear cassettes now i still need a new front middle chainring which i cannot find anywhere, all sold out

daviesee

windup wrote:

When I had a jumping chain it was due to worn chainrings - it also behaved well in the stand and I had just replaced the chain. Try spinning the cranks on the workstand with the brake held to give some torque.

Good idea but I can't simulate the same forces. The wheel either locks up or operates perfectly. Damn Koolstops

daviesee

Bikeit65 wrote:

same amount of links on each

Top Tip!

Unfortunately I threw away a few of my practice links last week. How many? !, 2 or 3??

Pity.

rhext

at 10K miles I'd suspect both cassette and chainring. Have a look at it: if the tooth profile looks like a shark's fin (so obviously more worn on one side than the other), that could well be your problem.

Thing is that chain and drivetrain wear together so you may well have no problem with the old chain.....but when you put a new one on, the links aren't as widely spaced as the old one and it doesn't mesh properly with the rest of the drivetrain.

rhext

Oh, I also had a similar problem on my MTB - turned out it was the freehub wasn't engaging properly, nothing to do with chain/drivetrain. Might be worth checking that too, if you can. Mind you, that would have probably given problems before you changed the chain.

daviesee

Thanks for the help guys.

Ribble have a sale on now which helps so I can try the cassette.
If there is no difference then I will need one some day anyway so may as well get it while it is going cheap :P

Any further words of wisdom in the meantime are still appreciated though.....