I knew it was time to replace my last cassette when I put a new chain on my bike and the chain would skip in a couple of gears. I couldn't tell what was wrong, took it to the bike shop, explained the situation, and was told that the cassette was worn out. New cassette = perfect shifting again.

Here's how to tell when your cassette is bad.

1) Is the chain "stretched"? If you can measure stretch, replace the chain and cassette.
2) Do you have 1 million miles? If yes, replace both chain and cassette.

Otherwise, never change it unless you just want something new, or if it's shifting like crap.

And mixing the cogs is perfectly fine as well.

Replacing a cassette every time you replace a chain is a waste of money.

Agreed. I just replaced the chain on my mountain bike showing nearly 1.0 wear on the Park tool and the new chain shifts perfectly with the old cassette. To be honest I figured I'd left it too late as I prefer to change at ~.75 wear but went ahead figuring there was nothing to lose with a quick test.

YMMV,

Hugh

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Genetics load the gun, lifestyle pulls the trigger.

I use the principle Rohloff uses for their cassette wear checker:




http://www.rohloff.de/en/products/hg_check/

Only I use a piece of new chain, without Rohloff's handle on it.

1. Engage four teeth,
2. pull the chain,
3. does the last roller grab on disengagement?
- If not, keep riding.
- If so, replace cassette.

In practice I almost never replace cassettes. I still ride Dura-Ace ti cassettes that I've used since 10 speed was new, including several seasons of 'cross. I replace chains though.

Cheers,

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Damon Rinard
Engineering Manager,
CSG Road Engineering Department
Cannondale & GT Bicycles
(ex-Cervelo, ex-Trek, ex-Velomax, ex-Kestrel)

I've wondered if there was an objective way to measure cassette wear. Nice to see there is.
Seems to me bike shop mechanics just tell me it looks worn, probably because they want to sell me a cassette.

agreed!

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2024: Bevoman, Galveston, Alcatraz, Marble Falls, Santa Cruz

Good rule of them is to change the cassette with the chain. I however am a small guy so I'm not putting the same wattage into my cassette as the bigger guys... I typically will go two chains per cassette.

You need to replace your chains more often then. If you did that, you'd virtually NEVER need to replace a cassette.

Since I learned about proper chain replacement intervals, I have literally not retired a cassette due to wear...or pretty much any other reason.

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http://bikeblather.blogspot.com/