I'm a bit confused - you'd had the bike for 5 weeks and presumably you'd been riding it for 5 weeks. It's unlikely 'chain stretch' would account for the derailleur somehow moving further to the left although I guess the mythical cable stretch might be possible (I've never in 30+ years of riding good bikes ever had an example of 'cable stretch'). Basically as Amaferenga suggests, you made a mistake changing down at the wrong time and got the chain wrapped round the chainring. I'm having difficulties seeing just where the seller is liable here. If it happened in the first week of riding - fair enough but not after 5 weeks. Commonsense would indicate that you check brakes and gears after a couple of weeks on a new bike - reason why many places offer a free 'service' after a month or 1000km, especially to newbies on their first decent bike, just to make sure everything's still hunky-dory.
Sorry but I think this is your screw-up
Hi fiona
Yes did about 300 miles in five weeks.
Didnt say cable stretch caused the failure-I claimed incorrect stop screw adjustment was the cause and that the damage was worse because it was a triple crankset.
The chain at no time wrapped round the chain ring-It got jammed between frame and chain-ring.
the reason it took 5 weeks to show was because I had never been in first gear in the 5 weeks I had bike-This was first time!
you assume Im a newbie making a mistake on my first decent bike-8000 miles in last 2 years and had my first +£1000 bike nearly 20 years ago .
Down shifting under pressure is not something i do and I cant remember the last time a chain came off the inside ring of any of my bikes.
But your fully entitled to your opinion.
cheers
