Chain skipping - diagnosis?

[GarethF]

I had the chain skipping on the tandem today, some help with diagnosis would be appreciated. Or in other words if anyone can identify the problem from the following description without me spending an extended period freezing in the garage or worse yet, outside, I should be most grateful....

Slipping drive chain using the smallest ring with the middle of the cassette(10spd), less severe on the larger sprockets. This was accompanied by very reluctant upshifting from small ring to middle.

It was rather difficult to see exactly what was happening at the back because it's so far away. I initially thought the problem was the timing chain but the cranks are still in sync.

My next best guess is insufficient tension in the rear skewer resulting in very slight ejection from the dropout(disc brakes). I haven't had opportunity to investigate this. Does this sound plausible? I suppose the clearance between the rear derailleur and the cassette is most critical in the lowest ratios- I ought to check this.

Thanks in advance....
Gareth

[NATURAL ANKLING]

Hi,
From little you have said, it sounds like the chain is worn and possibility also the cassette.
But you really need to examine the parts of drive chain or if you are not sure the someone will have to look at it / LBS.

How many miles the chain has done in what weather ?
Is chain (drive) stretched beyond 1% ?
Is the front small chain wheel and cassette worn with elongated slots / hooked teeth ?
Is the rear wheel secure ?
Is cassette firm or does it feel loose ?
Has rear derailleur any flop, side to side / leaning or bent ?
Does chain have any stiff links ?

[SimonCelsa]

spending an extended period freezing in the garage

maybe that's your problem, freezing conditions, long cable runs, icing in the housings somewhere??

I had a similar problem on my tandem a few years ago and it was ice/slush gumming things up,

all the best, Simon

[Tigerbiten]

My first thought was both new inner and outer cables, especially as you said you had trouble shifting.
Next was to clean and oil chain as you said it happened more at low tension, especially check for stiff links.
If that doesn't cure it then it start checking for bent/worn chainrings, sprockets, derailleurs, etc, etc.
But I'd start with the cables.

[pwa]

It's easy to check for stiff links, so I'd start with that. A combination of slightly inadequate lube and the cold might make links a bit stiffer than in warm weather.

I bet it is a cold related issue and goes away when things warm up.

[NATURAL ANKLING]

Hi,
In the days before cassettes'.........Violins.................I had a brass drift and a hammer to unseize my free wheel on frosty days

[GarethF]

The whole rig has only done about 400miles, so I think wear is minimal. I did wonder about stretch in the shift cable, although shifting without load (on stand) seems to be fine both up and down the whole cassette. We were fortunate in Durham having only very dry cold over the weekend so no slush on the bike. I will report back when I've had a proper look at it.

[Brucey]

could be stiff links, could be a worn chain.

400 miles is quite a long way for a 10s chain on the rear of a tandem; a good idea to check it for elongation while you are looking.

cheers

[rjb]

Here's a list of things which have afflicted my tandem over the years.
1) cables - I generally use any oil I have to hand but Brucey swears by finish line. I assume this is the ptfe grease.?
2) rear mech stiff. Apart from the pivots being stiff I have also had a parallelogram pin seize up. Clean and lub required.
3) cassette retaining nut coming loose
4) stiff chain links
5) freehub retaining bolt coming loose on a Shimano hub - this one was accompanied by a squirmy feeling as if the rear tyre was soft.

[lescargo]

Where in Durham are you?
Hetton or Hunstanworth?
Murton or Muggleswick?
If you want to pm your land line phone number I might have a few clues.

[GarethF]

Durham City (home of the pink panther!)

chain checker seems fine all the way along- in fairness I think at least half the mileage has been solo, even with my regular stoker the all up weight is only just 90kg, and we stick to fair weather as I'm hoping to maintain interest as they grow. But unless the presence of the crossover has some influence on the drive chain the wear oughtn't be so much different to my other bikes.

The current chain lube is some kind of wax, so it does feel a bit sluggish on the whole, and it could do with a wipe down and a fresh coating but I wouldn't say it was foul. The chain feels a bit slack over the back of the cassette possibly more so than on my triple equipped hack, perhaps interestingly the jockey cage seems to have less tension than the hack as well (tandem has XT rear mech, hack is SLX, both 3x10- those familiar with the streets of Durham will understand why this is necessary) and it's got to soak up an awful lot of chain to get from 48/11 to 26/36

I can't see any damage on the cassette, although with all the ramps and mismatched teeth I'm not sure I'd notice! Definitely nothing hooked or burred though. Hopefully the weather is warming up and I'll be able to get outside to try to reproduce the exact circumstances as I have the impression I'm not getting tension in the right places with the wheel off the ground.
G

[roubaixtuesday]

Suggestion that the derailleur connection to the dropout might have seized?

If it doesn't rotate freely that causes issues similar to yours.