Chain stretch dilema.

[Old Codger]

I have three flat bar chain checkers which I use and change my chains at 0.5%. I recently purchased one of those with the small pins and sliding gauge and printed on it it said that new chains can be between 0.25 and 0.5%.
Thinking this was strange I checked three new Shimano chains, one 12 speed and two 11 speed with all four checkers and sure enough all three chains were at 0.25%.
Does this mean that I should be going up to 0.75% before changing chains? What do people think?

 

[Pentti]

New chains are 0.00% - If your "checker" tells you something else it is not right for whatever reason.
Measuring roller centres is the only failsafe/accurate way to do it IMO.
I now use one of these stupidly priced, but deadly accurate devices....

LL Chain Wear Tool

Chain wear has become a little more complicated ever since 1x drivetrains have gained popularity. These drivetrains are designed to cross chain, something most of us were taught to avoid when we started riding bikes as a serious endeavor. Add to that the variables that flat top chains have...

www.abbeybiketools.com

 

[steve_sordy]

I always measure a new chain over 100 links, ie 50 inches. Then if it is different, (it never is) I can compare later.

Years ago, I used to measure with an internal vernier caliper gauge. The distance I measured was 5.7". A new chain was always 5.700". But when I started using 11 and 12 speed chains, the start measurement started to vary. (I suspect that the rollers were a different diameter to previous). Initially, if I recorded say 5.706" then that was the measurement I used to compare the same chain as it wore. But then I noticed that despite very careful measurement, often repeating the same measurent several times to ensure that I was as accurate as possible, the chain would vary along its length. What! Yes, using a vernier caliper, the chain would vary along its length, implying differential wear. It didn't matter how many times I measured the same section of chain I always got the same result, so at least I was consistent. Move the crank half a turn and measure again, different! This should be impossible as it cannot be manufacturing variation within the length of a single chain. I know how chains are made and it is unlikely to the Nth degree. Maybe the rollers are barrel-shaped, or maybe they do wear differentially?

So I stopped using my vernier caliper (more accurate than a go/no-go chain gauge.) Instead I started removing the chain and measuring across 100 links. This method averages out any section-to-section wear and reduces the error impact of any measuring-device-to-chain-contact variation by nearly nine fold.

What this says to me is that the short distance over which chain gauges operate cause them to be inheritantly inaccurate and can cause a chain to be retired long before it is necessary.

So if you have a chain that is due to be replaced according to your chain gauage, check the chain over 100 links and then make your decision. Measure with a metal tape measure, with the chain laid flat over a flat surface and pulled tight.
50" = new chain
50-1/8" = 0.25% = OK
50-1/4" = 0.5% = OK (As far as I'm concerned, but I'd buy a replacement ready for action. As long as the chain is running OK).
50-3/8" = 0.75% = replacement asap.

But you don't have to measure to the nearest one eighth of an inch. Most metal tape meaures have increments of 1/16". That is to 0.125%. That is more than accurate enough, but if you are careful, it is quite easy to meaure to 1/32" i(0.06%)! The choice is yours.

 

[irie]

I always measure a new chain over 100 links, ie 50 inches. Then if it is different, (it never is) I can compare later.

Years ago, I used to measure with an internal vernier caliper gauge. The distance I measured was 5.7". A new chain was always 5.700". But when I started using 11 and 12 speed chains, the start measurement started to vary. (I suspect that the rollers were a different diameter to previous). Initially, if I recorded say 5.706" then that was the measurement I used to compare the same chain as it wore. But then I noticed that despite very careful measurement, often repeating the same measurent several times to ensure that I was as accurate as possible, the chain would vary along its length. What! Yes, using a vernier caliper, the chain would vary along its length, implying differential wear. It didn't matter how many times I measured the same section of chain I always got the same result, so at least I was consistent. Move the crank half a turn and measure again, different! This should be impossible as it cannot be manufacturing variation within the length of a single chain. I know how chains are made and it is unlikely to the Nth degree. Maybe the rollers are barrel-shaped, or maybe they do wear differentially?

So I stopped using my vernier caliper (more accurate than a go/no-go chain gauge.) Instead I started removing the chain and measuring across 100 links. This method averages out any section-to-section wear and reduces the error impact of any measuring-device-to-chain-contact variation by nearly nine fold.

What this says to me is that the short distance over which chain gauges operate cause them to be inheritantly inaccurate and can cause a chain to be retired long before it is necessary.

So if you have a chain that is due to be replaced according to your chain gauage, check the chain over 100 links and then make your decision. Measure with a metal tape measure, with the chain laid flat over a flat surface and pulled tight.
50" = new chain
50-1/8" = 0.25% = OK
50-1/4" = 0.5% = OK (As far as I'm concerned, but I'd buy a replacement ready for action. As long as the chain is running OK).
50-3/8" = 0.75% = replacement asap.

But you don't have to measure to the nearest one eighth of an inch. Most metal tape meaures have increments of 1/16". That is to 0.125%. That is more than accurate enough, but if you are careful, it is quite easy to meaure to 1/32" i(0.06%)! The choice is yours.

I check a new chain (usually Shimano CN-9100) with a Park Tool CC-2 in several places then change the chain when it stretches more than 0.5% from that baseline (normally measures 0.0 when new). Simples.