Drivechain problem (not sure what)

[peanut]

Dropped into cycle shop on way home. They measured the chain and found it to be well stretched beyond its useful life, though the block was ok. Both changed at the same time.

New chain bought - may sort the problem.

you said the problem got worse after you last fitted a new chain and block.?
How can the chain be that worn unless you forgot to tell us you've done 15000 miles since then

 

[Zippy]

You got me there peanut. Definitely not done 15K to work and back over past 12 months!

The technician was from Halfords , but the chain ruler did show chain stretch (he showed me) - maybe a rubbish chain (from Halfords?).

Time and a chain change will tell.

 

[peanut]

well I'm still far from convinced but time will tell.

A lengthened chain won't exhibit the fault that you have described. it will tend to ride up onto the tops of the sprocket teeth , not try to climb up onto the adjacent sprocket . The latter problem has nothing to do with chain length but everything to do with cable adjustment and tension.

Incidentally a chain doesn't actually stretch . Its a little bit of wear in all of the links of the chain that accumulatively makes the chain longer and the gap between each roller slightly larger.

 

[Zippy]

So embarrasing! I took my problem to the local cycle repairs and they found the problem straight away. It was one of the chain links had snapped on one side so it looked ok, but opened up under high pressure like hill climbing. One split link later the cycle was fine.

I am going to replace the chain asap though. Obviously on its way out.

 

[peanut]

not embarrasing at all. I doubt anyone would have spotted a broken chain plate especially on the hidden side. Glad you have it sorted now. An unusual and as far as I know pretty uncommon failure. (cue loads of 'it happened to me' posts ) THanks for coming back to post the outcome.