Accelerate, kerchung, broken plums

[fatblokish]

Evening all,

Fettled my bike at the weekend, good old clean, new brake and gear cables, tighten cones etc.

I also replaced the old chain with one from KMC, included the missing link and put on a new freewheel (Shimano 105).

Now whenever I put down the power, something gives an almighty clunk and I wreck em on the top tube.

I have a triple ultegra on the front and the issue occurs irrespective of which ring I'm in. I remembered to shorten the new chain to match the old (116 links IIRC).

I'm unsure if the chain is slippling on the front rings or rear. Earlier today it slipped off the middle front ring at a set of traffic lights.

Your thoughts please.

Ta

 

[just jim]

Maybe the freehub body is worn. They can do that. It can hurt.

 

[gbb]

How old is your cassette ? Never experienced it myself, but new chain on an old cassette reputedly does that...the old chain meshed to an acceptable degree, but a new chain won't.

 

[fatblokish]

Sorry, just realised that freewheel is olde speak.

Yes, the new cassette was put on also at the weekend, so far it seems to recur in any gear (I need to shove a towel down my shorts before I repeat any experiments), every time I put down power of 70% or more. Otherwise it runs as smooth as silk, no probs with gear changes in any combination (avoiding the big-bog and small-small combinations).

When I changed the cassette there appeared to be no wear at all on the outside of the freehub, and the problem only began after I had made the changes.

 

[Kestevan]

Sounds like its slipping alright. If you changed the cassette at the same time as the chain, it does tend to point to the chainrings as the culprit. Are the noticeably worn or sharktoothed?

 

[2Loose]

It sounds like a jumping chain which could mean the indexing is out slightly? A new chain and cassette could suggest the chain is being deflected at some point, stiff link where it was joined perhaps? Or incorrect chain routing over the guides near the jockey wheels (it happens

)? Unlikely all three chainrings would be worn that bad...

 

[the snail]

wrong size chain maybe?

 

[andrew_s]

Worn chainrings will slip, and slipping damages them further so the pressure required to provoke slip gets less quite quickly.

 

[just jim]

Sorry, just realised that freewheel is olde speak.

Yes, the new cassette was put on also at the weekend, so far it seems to recur in any gear (I need to shove a towel down my shorts before I repeat any experiments), every time I put down power of 70% or more. Otherwise it runs as smooth as silk, no probs with gear changes in any combination (avoiding the big-bog and small-small combinations).

When I changed the cassette there appeared to be no wear at all on the outside of the freehub, and the problem only began after I had made the changes.

Dunno if the freehub body is the problem, but the wear could be internal. When I stood on the pedals an audible crack would sound from the cassette and the chainwheel would spin freely. Slower speeds and it would function. LBS should take a look maybe?

 

[frank9755]

Sounds like the chainring/s

A worn chainring can work ok with a worn chain but when you put a new chain on it often slips.
- The old chain had stretched links which matched the increased pitch of the worn chainring better.
- New, unstretched chain will have shorter pitch hence slippage.

 

[fatblokish]

I changed all three rings, and the problem has now gone.

The middle of the three rings was worn, but not unduly so.

Anways, thanks for the guidance.