How to Measure a Bicycle Chain
I wrote this page out of frustration. I had a bicycle, I had a dial caliper, but I had no instructions on how to determine if my chain is stretched and needed to be replaced. From searching the internet I found that one way was to measure 24 links with a steel rule from pin to pin. 24 links would be 12" on a new chain. Some people suggest that you change the chain at 0.25 to 0.5% stretch. This translates to 0.030" to 0.060" in 12". This small distance would be difficult to measure accurately with a simple ruler.
The other way would be to purchase a chain gage. These are purpose built tools tools that measure 2-3 links and are either go/no-go type or give a simple wear scale. They are compact and easy to use, but cost $10 to $30.
My issue is that I already have a nice dial caliper that can measure up to 6" to within 0.001". All I needed was the measurement of a new chain. The other minor complication is that I need the dimension from the inside to inside of the pins.
Here is a picture measuring 12 links on a new and unused chain from inside to inside of the pins. The dimension is 5.700". Click on the picture to see a bigger view.
Here is a picture measuring 12 links on a used chain with about 1500 miles on it. The dimension is 5.727". Click on the picture to see a bigger view. This chain has (5.727-5.700)/5.7*100=0.47%. Time to replace this puppy.
Wear Table Measurement Percent Stretch 0.25% 5.714" 0.5% 5.729" 0.75% 5.743" 1.0% 5.757"
I hope this information helps you.
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