When to change your cassette

I am no bike guru but I do find using the chain checking ruler like thing works well for me - vid below explains how to use it

https://www.youtube.com/watch?v=EJfTulNH4sk

https://www.amazon.co.uk/Park-Tool-CC-3-2-Chain-Indicator/dp/B000BR3LHQ/...

Rohloff, in a bizarre twist, sell a cassette wear checking tool.  

I have only just started keep track of this. Before I just took the bike to the lbs and they always said chain needs replacing as does the cassette and that's probably true as I never cleaned the drive train. Now I regularly clean and check the chain. 105 chain lasted 1600miles (sorry still work in miles) before it allowed a 0.75 chain checker to slot in. Having changed the chain twice and having some slippage I would say if you get 4000 miles out of a cassette you are doing well. That is less and a penny a mile! So don't be stingy

As I understand it, the more stretched your chain is, the more it prematurely wears the cassette, as a stretched chain engages on fewer teeth, wearing it more. So, in one respect, any ratio of cassettes to chains is achieveable. If you are on the conservative side with your chain and throw it out sooner, not only are you increasing the "chains bought" side of the equation, but you're reducing wear on the casette, and reducing the "cassettes bought" side of the equation. I've heard numbers as high as 7:1, but that would be by throwing your chain out before it really hits that tipping point of wearing the cassette prematurely. 1:1 and 1:2 are in my opionion too far the other way. In reality, you're eeking too much out of your chain at the expense of the cassette.

I work to about 3:1, 2000kms for the chain (probably throwing it out a bit early) and 6000km per cassette.

I tend to change chains at about 1,200 miles when the .75% indicator looks like it's thinking about slipping through in the next couple of months or so. I've been through 3 chains on both bikes and the cassettes both look and feel fine.

My mate on the other hand who is not remotely mechanically minded just rides the living shit out of his bike and replaced the whole drivetrain when everything's absolutely on it's last legs and slipping .

A cassette per chain? I don't think so. My current cassette has been through at least 5 chains (Ultegra cassette, 105 / ultegra chains. So long as you change the chain before it is over-worn then you should get very little sprocket wear (they are hardened steel after all). I do 10 - 13,000 km a year and race regularly. Like chains, keeping them clean is important. As an aside, I don't believe your couple of skipped teeth was the chain 'bedding in' by altering any property of the chain. It's much more likely it was derailleur mis-alignment or something similar. Sounds like you're doing exactly the right thing by checking chain wear and replacing regularly. I reckon to get over 20,000km per cluster. (80kg, cat 2)

CHAIN ROTATION!

Depending on the cost of chainrings/cassette (it can vary a lot) it's best to run 2-4 chains in rotation.

Rotate them say 300-500 miles (it takes seconds with quick links) and simply use the whole drivetrain as long as you can.

Using this method you will never throw away any chain too early or replace it too late. No need for a wear indicator either, ever.

From the "point of view" of other drivetrain components, using x number of chains in rotation is like running a single uber chain with 1/x of wear rate. The wear on components is reduced, especially in the beginning.

One more overlooked advantage is ability of using another chain in case of a serious mechanical that damages the current one (chain suck, rear mech in spokes drama etc...) You know that at least one of the other chains will mesh with other components.

I change chains once they get to 0.75% worn, and try the new chain on the old cassette first.  Doing this, cassettes seem to last at least for 4 chains, and I've never needed to replace a chainring yet

I tend to replace both every 3k miles - so 3/4 times per year. Keep everything nice and clean, not too much lube, not too much degreaser. I've done 23,000 miles in the past 3 years and have changed one chainset (but because it was flimsy, not worn).

I have various wheels and cassettes so it can be difficult to track exactly how often everything gets changed, but as long as I change the chain at, or before, 1% stretch on my fat spanner gauge (which I think exaggerates wear) then I find that cassettes last ages - i.e. almost never change them. I have a cassette that is 10 years old on the wheels that I have relegated to the turbo and that runs okay with a new chain.

I do get through chains regularly though! I use KMC X9 and X10s on various bikes.

What chains are you using / buying, out of interest. 

I normally reckon on 3 chains per cassette and 3 cassettes per chainset. Seems to have worked out OK so far...

Sound advice from Simon. You need to change cassette with chain if you only change chain when you can feel a problem. If you keep an eye on your chain and change it early you could get two or three chains to one cassette.

Buy a new cassette (you'll need it at some point regardless).

Fit the chain.

Take it for a test ride.

It is likely to skip on the most used cogs first. If it does then replace the cassette.

Two chains per cassette is fair but I think it depends on how long you let the chain go between changes, among other things.

Helpful video here - http://www.artscyclery.com/learningcenter/determiningcassettewear.html