Ask the Bike Doc: 10. "When should I replace my chain and cassette?"

Words by Aaron Scott

on 29/08/2013 17:50:00

kmc-8spd-bike-chain

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LP: Hi Bike Doc, I replaced my chain last week after 1800 miles and when riding out to Fineshade it was slipping under heavier pedaling load in some gears. On the return journey it was much more settled and I hardly noticed it at the end of 50 miles. Probably left it a bit long to replace the chain but in your experience if it fully settles down in the next 50 miles have I averted cassette damage or should I be considering replacing the SRAM PG850 on my bike? Also, what should I look for when inspecting the cassette?

Bike Doc:  Hi LP, what you will find is that as a chain wears, it will inevitably stretch. You will find that after approximately 1000 miles a chain is worn and begins to then stretch open the teeth on the cassette. This then means that when you fit a new chain it doesn't fit onto the teeth correctly and in turn slips over them. Ideally you should replace the chain and cassette at the same time, the reason it seemed OK is down to the fact that not all of the sprockets on your cassette will be stretched  Just the more commonly used ones.
Unfortunately, the only real way to monitor this and prevent it from happening is to buy yourself a chain wear indicator tool and some good quality chain lube. Always clean your chain before applying chain lube and keep an eye on your chain for wear.

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