According to the international standards, ISO-9633, the method to evaluate the chain’s stretch is to measure the length between 2 pins.
However, the measurement could be completely different nowadays as most of the tools measure the chain stretch between 2 rollers. This method will cause a huge difference when you try to evaluate the chain still working or not.
So what do we do?
Analogy- Using a Ruler for testing
“Inch” is the basic unit for all types of chain. Each link length is 1 inch (length of 3 Chain bolt) and the length between the two chain bolt is 0.5 inches.
As a result, the testing point is the middle of the pin and we usually choose 6 inches of chain to test the extension.
If 1% of the tensile rate will be over the standard, the chain needs to be replaced
If the length of stretching is more than 1/16 inches, this chain should be replaced as well.
If the length of stretching is more than 1/8 inches, we highly recommend that not only the chain but also the cassette sprocket should be removed together.
Transfer the chain to the outermost wheel then pull up from the middle of the tooth plate
If you can easily pull up the chain from the cassette, which means the gear is already damaged. Both the chain and the cassette sprocket should be changed in the meantime.
Please note that TAYA’s safe margin of chain stretch is between 0.4 to 0.8 percentage via park tool.
Perfect maintenance extends the lifespan of the bike chain. The longer the chain life maintains, the more joy of your riding could remain.