Cassette wear - how to check

I suspect shops always say you need a new cassette because that is how they make money.

Would be interested to hear an answer on this one but I think it comes down to skipping chain - and that isn't definitive as a somewhat worn cassette will often skip for the first thirty miles or so then be fine, once it has bedded in.

i keep meaning to draw an outline stencil of my next new cassette then when i do a deep clean i.e. once before the end i can compare it to new.

You cant see cassette wear unless it's very worn but experience shows it.

We dont change cassette for the sake of it but if a bike come in like today with a well worn chain we know the cassette is toast. If the bike is well maintained and we see it regularly then the chain gets changed and not the cassette.

The 0.75% limit is junk. If the chain is changed at 0.75% but the cassette is kept then a test ride is need with 800w sprints to find out of the chain skips. To do that in all gears is not practical . The risk of the bike coming back is too great so cassette get changed of we are unsure of the cassette will be o.k. you see it might be fine initially but after 500 miles it might not be. Skipping might start or the shifting gets iffy. That the shops reputation right there going up in smoke.

One of own bike with a campag 11 speed 12-27t chorus cassette had it chain changed in time or so I thought (kmc 11-93 changed at 0.75% wear). All looked well until I shoved out power (500+W) I and the chain skipped on the 12t cog. That was the second ride with the new chain however with so many bikes I can not remember how old the cassette is. I think its seen more than one chain. The moral is you cant see cassette wear and while for our own bike we will try and see good results cannot be guaranteed. All you have to do is leave a smidge too long and ride that small cog alot and the cassette. is ruined.

So forgive shop for playing it safe. In our experience changing the cassette and chain together is the safe thing to as most of the time whe we see a bike the smchain has been on there for some time. You keep the cassette if you change the chain early. 0.5% wear is the limit to get 3 or 4 chains to the cassette. Campag have a different measure using a vernier. Change cassettes early and the cassette survives for many chains.
At 0.75% it can be toast even after one chain.


In my experience once skipping starts its does not go away. If it does go away it has not. All that has happened your chain has worn prematurely on the worn sprockets so now you have a worn chain on a worn cassette.

However if we change the cassette at 0.5% wear the customer thinks we are having them on.

Also mileage is not a good indicator. In winter I dont even get 1000km out of a good chain on the road. In summer I can get 3000km from a chain if it's a campag effort. Kmc last 2000km at best. Power, the gear you ride in (small cog users get more chain and cassette wear more quickly) and conditions all affect wear.

The best way of getting the most from a cassette is to start with a cassette and every 1000km change the chain until you have 4 chains. Keep the old chains and rotate putting the first chain after the fourth is done. That way very long cassette life can be achieved but it too much effort for me. 23 bikes means nearly 100 chains on the go. No thanks.