Written by: Lauren Enghien and Mona Noujeim
The largest yearly sporting event worldwide just started next Saturday: it’s the Tour de France! While the riders are a big factor in this stage ride, the Nikon Metrology X-ray team took a look at one of the most critical parts of the bike itself, the chain. While experienced cyclists know how important the maintenance of the chain is, maintaining it is often forgotten.
So what happens precisely over time with your chain?
Due to the forces being transmitted by the chain while your peddling, the chain will extend over time. This can be measured using a simple gauge that measures the pin distance. Depending on the chain, they typically need replacement after an extension of about 0,5%. If the distance gets any longer, this will also affect your gears up until a point you will also have to replace those making the replacement cost a lot bigger.
Lauren Enghien, Application Engineering Manager, used the Nikon MCT to measure what happens to the chain using a used chain and a brand new one. While the average distance between the pins should be 0,5 inch (12,7mm), the distance in the old chain was about 12,77 mm which is an extension of about 0,6% which is above the recommended replacement factor.
Using a helical CT scan where we both rotate the part and move the part upwards, we were able to get a closer look at the chain maintaining the highest resolution. In the reconstructed volume, it can be seen what happens on the inside of the part. The part surrounding the pins is no longer as tight as the new chain even showing a serious gap. We can also see a lot of dirt inside the used chain that can cause additional friction and reduce the performance of the chain and increase the wear.
Measuring the circularity, we see a serious extension. Where the new chain remains within 30µm tolerance of roundness, the old chain shows large deviations of above 100µm.
In conclusion, we can say that it’s important to maintain your bike including your chain and gear as this will not only decrease your performance but can cost you a lot of money if you forget to replace it.
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