When is it best time to replace bike chain to prevent any cassette damage?

[Lauris]

Today I checked bike chain stretch is at 0.75.
So should I replace the chain now? To avoid cassette damage or wait for 1.00. I don't want to replace the cassette at the same time as this will be quite expensive for me.
I've only done around 900 miles on this chain, meaning that I would have to change the chain every two/three months or so. If changing at 0.75. (Which would be expensive over the year) And even more, if changing the cassette at the same time.

How do you guys treat this problem?

 

[Ming the Merciless]

Yes 0.75 to avoid cassette also getting worn. Wear will have been much greater over the winter with the weather and skog on the roads. The replacement will wear less as you move into Spring / Summer

 

[Drago]

I'm lucky to get 1500 miles from a chain (heavy and powerful rider).

I treat the problem by buying a new chain every 1500 miles. Compared to the cost of 1500 miles worth of fuel, insurance and dar tax its piffling.

 

[boydj]

Chain wear is as much due to the riding conditions as it is to the rider. All-weather commuting in the winter could wear out a chain in as little as 500 miles, while a chain on a good weather only bike could last 2000 miles. I'd replace the chain now before the cassette gets any more worn. You'll be able to use the second chain for longer because the cassette will be needing changed by the time the second chain is worn out.

 

[ColinJ]

Chains can tend to get worn more quickly at this time of year because of wet salty grit getting flung up onto them by front wheels, unless you have mudguards with big flaps on them. Chains last much longer the other 3 seasons.

PS Curses - beaten to it by @boydj!!!

 

[raleighnut]

The sprockets will still wear even with new chains but changing them at 0.75 helps delay it. I'd keep the old chains and when a new one will not mesh and skips guess what one worn to 0.75 will run fine on that cassette.

 

[Racing roadkill]

It depends on the chain. 0.75 is ‘your chain’s getting a bit past it’s prime’ 1.0 is ‘I’d change the chain now if you don’t want to start hacking the cogged gear wheels up’.

 

[slowmotion]

I change mine when it gets to 0.5%. Some say that it's extravagant, but I use cheap chains. The cassette gets binned after two or three chains.

 

[SkipdiverJohn]

How do you guys treat this problem?

Simple, I keep my chains clean and lubed but I don't bother measuring wear and I don't change anything unless the chain starts skipping over the sprocket teeth under load. If that happens I look for a better secondhand chain to fit from my spares pile.

 

[Racing roadkill]

Of course it very much depends on the chain and sprocket cassette. I wouldn’t want to risk damaging a SRAM Red eTap AXS set up ( for example ) because they cost a fortune ( relative to a hairy arsed fixie / SS ). So I’d be far more cautious about letting the expensive chain get to the point it’s hacking the expensive sprockets up.

 

[SkipdiverJohn]

Of course it very much depends on the chain and sprocket cassette. I wouldn’t want to risk damaging a SRAM Red eTap AXS set up ( for example ) because they cost a fortune ( relative to a hairy arsed fixie / SS ). So I’d be far more cautious about letting the expensive chain get to the point it’s hacking the expensive sprockets up.

Agree completely, but that's why I stick to the simple, cheap and well-proven transmission set ups such as 3-speed IGH, and 5/6 speed freewheels combined with square taper steel chainring MTB triples up front. Not only is the stuff cheap to replace new and readily available used off scrap donor bikes, but they don't even seem that prone to wear in the first place. I can find & salvage them used faster than I can actually wear them out.

 

[Ajax Bay]

bike chain stretch is at 0.75. So should I replace the chain now? To avoid cassette damage or wait for 1.00. I don't want to replace the cassette at the same time as this will be quite expensive for me.

At 0.75% chain elongation (NB not 'stretch': nothing's stretching), you have left it too late to change it and expect the cassette to be content with the new chain.
Your best approach is to leave the matched chain and cassette to happily grow old together. Very likely you'll get another 1000 similar type riding miles. Then the chain will slip on the most used (and therefore worn) sprockets. Well before then, you will have bought a new chain and a new cassette, spreading the cost over to months if needs be (you haven't shared what speed your drivetrain is). When you get the slippage, change both chain and cassette at the same time. If the cassette is expensive, then resolve to measure more often, with care and accuracy, and change the chain once it gets to 0.5%. That way you'll get likely 3 chains per cassette (this is in line with @slowmotion 's advice/observation). The more expensive the cassette the more attractive this is, from an economic PoV.

 

[slowmotion]

One thing that I've always wondered about is how to tell if your cassette is due for replacement. Does anybody know?
Thanks.

 

[Pale Rider]

powerful rider

Who have you been lending your bike to?

 

[raleighnut]

One thing that I've always wondered about is how to tell if your cassette is due for replacement. Does anybody know?
Thanks.

Oh that's easy, when you fit a new chain and it jumps on the rear sprocket. If however you've saved an old chain or 3 they'll run fine on the slightly worn out bits.