Jumping chain

For discussions about bikes and equipment.
landsurfer
Posts: 5081
Joined: 27 Oct 2012, 9:13pm
Location: Rotherham

Jumping chain

Postby landsurfer » 11 Sep 2016, 5:48pm

So .... new front sprocket, Stronglight, new freewheel cluster, same as removed, new chain.
Now when I pedal under load, climbing etc the chain jumps.
HELP
The Road Goes On Forever

Steve
Posts: 216
Joined: 2 Apr 2007, 1:42pm

Re: Jumping chain

Postby Steve » 11 Sep 2016, 6:04pm

The first things that spring to mind are to check that chain length is correct, and that the rear mech is functioning properly in taking up slack. Does it slip on all the sprockets or just the smaller ones?

User avatar
Mick F
Spambuster
Posts: 48202
Joined: 7 Jan 2007, 11:24am
Location: Tamar Valley, Cornwall

Re: Jumping chain

Postby Mick F » 11 Sep 2016, 6:08pm

Providing you have a new chain, new sprockets and a new chainwheel, all should be perfect.
Was it jumping before you changed stuff?

I agree with Steve. Make sure the chain is the correct length.
Mick F. Cornwall

landsurfer
Posts: 5081
Joined: 27 Oct 2012, 9:13pm
Location: Rotherham

Re: Jumping chain

Postby landsurfer » 11 Sep 2016, 6:24pm

Only jumps on the smallest 3 sprockets. Did not jump before.
Microshift system.
Stronglight compact Chainset from SPA, run with the inner 36 tooth ring only as an 8 speed transmission.
36 tooth ring mounted to the inside of the spider as designed.
This is my bomb proof, all weather, all event, Triban 500 .... or it was ........
The Road Goes On Forever

Mike Sales
Posts: 4440
Joined: 7 Mar 2009, 3:31pm

Re: Jumping chain

Postby Mike Sales » 11 Sep 2016, 6:34pm

The first and easiest problem to look for is a stiff link, which might be the one just joined.
Backpedal and watch the derailleur arm. If it twitches forward move the crank back and forth watching where the chain runs over the pulleys. You may see that one link does not articulate fully. If this is so, there is your problem. The problem will be worse on the smaller sprockets because the chain has to bend most to go round them.
Try bending the chain at the suspect rivet. If you have found the stiff link take the chain in both hands, one either side of the culprit, with thumbs close to the rivet. Forcibly try to bend the chain at 90 degrees to the usual bend. This should lever the side plates a fraction further apart and cure the stiffness.
Or you could use the spreader fingers on a Cyclo Rivoli chain tool to achieve the same end.

User avatar
531colin
Posts: 12633
Joined: 4 Dec 2009, 6:56pm
Location: North Yorkshire

Re: Jumping chain

Postby 531colin » 11 Sep 2016, 7:09pm

Jumping on the same sprocket, or ghost shifting (trying to change gear)....?
landsurfer wrote:Only jumps on the smallest 3 sprockets. ..........
Stronglight compact Chainset from SPA, run with the inner 36 tooth ring only as an 8 speed transmission.
36 tooth ring mounted to the inside of the spider as designed.................

So you are running a single ring on the small ring position and crossing the chain over to the top sprocket?
I think I might have used the big ring position and fitted a BB say 5mm shorter than normal (for a double chainset) to put the single ring half-way between the position of the big and small rings.

landsurfer
Posts: 5081
Joined: 27 Oct 2012, 9:13pm
Location: Rotherham

Re: Jumping chain

Postby landsurfer » 11 Sep 2016, 7:26pm

Good point Colin but it worked fine before.
Could it be the LACK of wear in the new chain ?
First thing I did was to check for a tight chain link but no stiff links apparent.
It is normal to run the chain from the small chainring to the largest sprocket on the freewheel when climbing.
If I could recover the original chain I would refit it to see how it runs . . . But the binman beat me too it.
The Road Goes On Forever

Brucey
Posts: 37358
Joined: 4 Jan 2012, 6:25pm

Re: Jumping chain

Postby Brucey » 11 Sep 2016, 7:42pm

landsurfer wrote:Could it be the LACK of wear in the new chain ?


I have seen this once or twice. Of course a new chain will often jump if it is used on worn sprockets, but I have seen a new chain jump on new sprockets once or twice too. IIRC the chain measured slightly shorter than 1/2" nominal and soon settled down once there was a few miles on it.

BTW fitting an old chain to new sprockets won't prove much; this combination usually works OK but wears the sprockets double-quick.

NB if there is just one bad link ( eg stiff link or badly assembled quicklink) it will manifest itself once every three turns of the pedals or so with a 36T chainring.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

User avatar
foxyrider
Posts: 4717
Joined: 29 Aug 2011, 10:25am
Location: Sheffield, South Yorkshire

Re: Jumping chain

Postby foxyrider » 11 Sep 2016, 7:59pm

Is that like a skipping rope but in metal? :D
Convention? what's that then?
Airnimal Chameleon touring, Orbit Pro hack, Orbit Photon audax, Focus Mares AX tour, Peugeot Carbon sportive, Owen Blower vintage race - all running Tulio's finest!

User avatar
531colin
Posts: 12633
Joined: 4 Dec 2009, 6:56pm
Location: North Yorkshire

Re: Jumping chain

Postby 531colin » 11 Sep 2016, 9:12pm

landsurfer wrote:Only jumps on the smallest 3 sprockets............

landsurfer wrote:.....It is normal to run the chain from the small chainring to the largest sprocket on the freewheel when climbing.......

as you say, it might wear in