New chain

For the sake of £30 I think it is the best money I have spent in a long time.  Not too sure of the science and I am sure someone will post a comment but I haven't changed my chains as much this year, but a bit of free time last week and I changed a few over. I have one of those chain tools to see if they are stretching and they were close to needing a change so I did it and I swear it has made a difference to the drive train. I guess it saves wearing out the cassette and chainrings as well.  So if you need a wee boost treat yourself to new chain.