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.

Ride Safe,

Joe


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