I have one of those chain wear checkers that tells you when your chain is worn out. It gives 75% and 100% readings.

If its just dropped on to the 100% reading (last weekend it wasn’t), then is it likely my cassette is finished too?

i.e. are these things designed to tell you when to change your chain BEFORE it wrecks your cassette? Or am I too late?

There’s so many out there. Which on do you have? They generally tell you the chain has gone before it really has and they are flawed in that they push two rollers apart. The shimano one avoids this but is expensive. Take the chain off and measure the longest length you can with a steel rule. 5% lengthening is the cut off point really.

they are flawed in that they push two rollers apart

that’s the whole point, they’re worn so can be pushed apart.

how u-shaped and symmetrical are the cogs on your cassette? that’s the real test.

I’d start by getting a new chain* and if you don’t get any slippage then you’re fine

*a stitch in time etc etc…

But you get a more accurate measure if you push both rollers in the same direction. By pushing them apart, you also include the original clearances which over such a short length introduce a massive margin of error. The only good news is that this causes people to bin chains earlier than they need to.

0.75% is the heads-up to start looking for a new chain. 1.00% means do it now. As for 5 % wear…Err, no comment.

Personally I’d change the chain when the indicator shows it’s at the 0.75% worn. If the new chain’s jumping on the old cassette then it’s time to consign that to the skip too.

Have a look at this Park Chain Checker This is the one I use 8)

D.

Dave, good spot, that should read 0.5%.

Mtbtomo, are you sure your checker reads %? My rohloff one gives 0.075 mm on side and 0.1 mm on the other. With measurements this fine, you can see why pushing two rollers apart can give a false reading. What you really want to know is whether or not they’re multiples of half an inch when loaded in the same direction.

If the new chain’s jumping on the old cassette then it’s time to consign that to the skip too.

This. Put a new chain on yesterday…quick test ride and the chain skipped on nearly every cog 😳

New cassette now installed, and new middle ring on order. Jockey wheels where also like throwing stars so new ones of those installed. The constant grinding joy of winter riding 🙁

My dad has one that I bought him years ago, can’t remember the make without checking CRC orders but 75% was change the chain and 100% was drive prob needs replacing.

this makes a lot of sense on the subject and is perhaps a better explanation of the points I was trying to make

mybchain checker shows 0.75% and 1% wear. Change chains at .75% you probably don’t need to change anything else. Wait until its more worn you need a new cassette.

If I don’t catch the chain at .75% wear I just leave it until the whole drivetrain is worn out.

I usually get 3 chains to a cssette

as per Davesport is how I always thought you used them and it seems so do the jurnos in his link, but according to the instructions on the Park Tools packaging. .75% is where some chain manufacturers recommend changing the chain, Other chain manufacturers recommend changing the chain at .1%, check with the manufacturer.

AS an aside I have checked the measurements the cheapo tool I have gives me against a whole chain measurement and its very accurate. Its a park tool one that hooks into the chain. However when it say 0.75% wear over a hundred links thats what the chain has.

Yep, its 0.75% and 1.00%.

Its one of these by Cyclo…Cyclo chain wear indicator

The 1.00% just fits now, it didn’t last week. Think I might just leave it all and let it all wear out, I want a larger top sprocket anyhow.

Tomo, most chain checkers give a premature wear reading. Get a steel rule and measure 12 pairs. If they’re less than 12 1/16 inch (a real world 0.5%) you should get away with a new chain.

If you favour one particular sprocket at the back, you may have worn this. Have a look at the link I posted, I learned a lot from it. Realised that the checkers are good as a rough guide but no more.

Why not just buy a chain & cassette at the same time? You can fit the chain, take it up & down the road and see how it goes.
If it skips then stick the cassette on.

You’ll need the cassette at some point anyway so you aren’t wasting money, just potentially spending it early…