We’ve tested 12-speed Shimano chains before and that wasn’t too much work. With minimum maintenance and maximum motor assistance, we could finish the test in months. Not this time though. 10-speed chains last longer. And these are both ebike-specific chains, which usually means heavier and more durable.
Practically none of the demo bikes we receive have 10-speed drivetrains. So, we ended up outsourcing the chain to a neighbor riding a non-assist commuter bike. Unfortunately, the result of this test isn’t comparable to the 12-speed results as this was a milder test where the chain was exposed to much lower pedaling power.
*Prices from a random Webshop, bike24.com
** Length cut to fit the bike
Before installing the chain, we measured it to determine pre-stretch. Some chain brands have a bit of stretch when new. The KMC measured 0.00 mm stretch, and we struggled to get the measuring device in. The Shimano was 0.02-0.03 mm measured at random spots. Having a bit of pre-stretch isn’t necessarily a big deal, but it’s interesting to know when determining chain wear.
You might be used to reading chain stretch in %. Our new KMC Digital Chain Checker measures in mm (or inches). But as the tool measures 4 full links which is 101.5 mm, the result ends up being about the same in mm and %.
Corrected for pre-stretch, the Shimano chain has stretched about 0.25 mm over 2.500 km. I think that’s fine. If we go by the recommendation printed on the KMC chain tool, the Shimano E6090 10s is about half-way to being mildly worn. KMC defines 0.8 mm as excessive wear. The Shimano chain should last another 5.000+ km and that’s fine for a cheap chain.
The KMC e10 seems to be a tenth into its lifespan. That indicates this chain will go 20.000 km, provided chain wear is linear. That doesn't sound realistic. But this test isn't done on an ebike, we will never get close to those figures on an emtb. Based on our measurements, it has seen one third of the wear found on the Shimano chain.
We didn’t snap any chains during this less extreme test. Therefore, the KMC is the winner of this test with quite some margin. Allthough, it might be the KMC e10 EPT is the true winner.
Practically none of the demo bikes we receive have 10-speed drivetrains. So, we ended up outsourcing the chain to a neighbor riding a non-assist commuter bike. Unfortunately, the result of this test isn’t comparable to the 12-speed results as this was a milder test where the chain was exposed to much lower pedaling power.
| Shimano E6090 10s | €25* | ~270g** |
| KMC e10 | €25* | ~240g** |
** Length cut to fit the bike
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Ending the test at 2.500 km
None of the chains are close to being worn out. But we are seeing differences and it’s been almost 2 years, so we had to finish this. The test is done by cutting two chains in half and making a chain consisting of half a Shimano E6090 and half a KMC e10. This ensures both chains are ridden in the same conditions and receive the same maintenance.Before installing the chain, we measured it to determine pre-stretch. Some chain brands have a bit of stretch when new. The KMC measured 0.00 mm stretch, and we struggled to get the measuring device in. The Shimano was 0.02-0.03 mm measured at random spots. Having a bit of pre-stretch isn’t necessarily a big deal, but it’s interesting to know when determining chain wear.
You might be used to reading chain stretch in %. Our new KMC Digital Chain Checker measures in mm (or inches). But as the tool measures 4 full links which is 101.5 mm, the result ends up being about the same in mm and %.
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The result
After about 2.500 km, the results are in. And they leave no doubt, the KMC has seen much less stretch. Five random measurements showed 0.04 to 0.08 mm stretch for the KMC e10 chain. While five random measurements showed 0.23 to 0.29 mm wear for the Shimano E6090 10s.Corrected for pre-stretch, the Shimano chain has stretched about 0.25 mm over 2.500 km. I think that’s fine. If we go by the recommendation printed on the KMC chain tool, the Shimano E6090 10s is about half-way to being mildly worn. KMC defines 0.8 mm as excessive wear. The Shimano chain should last another 5.000+ km and that’s fine for a cheap chain.
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The KMC e10 seems to be a tenth into its lifespan. That indicates this chain will go 20.000 km, provided chain wear is linear. That doesn't sound realistic. But this test isn't done on an ebike, we will never get close to those figures on an emtb. Based on our measurements, it has seen one third of the wear found on the Shimano chain.
Another KMC e10 chain
Looking at bike24.com, you might notice there is also a KMC e10 "EPT" version. We received one of these too, but it wasn’t included in the stretch test. I found the EPT chain for €33, about €8 more than the regular KMC e10. EPT is a coating meant to improve rust protection. I mounted this chain on a bike that wasn’t ridden many kilometers, but it was left outside through an entire Norwegian winter and then some. After almost a year, without being lubed, it still looked fine. For a long-lasting chain, it might be the rust and not the stretch that kills it. In that case, it makes sense to go with the EPT version.|
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Conclusion
Why is a new Shimano E6090 chain stretched? I can only speculate, but the E6090 has a bit more sideways flex. This might put less stress on the chain when shifting under load. Perhaps the Shimano chain will be less prone to snapping? I have no idea, but Shimano might very well have their reasons.We didn’t snap any chains during this less extreme test. Therefore, the KMC is the winner of this test with quite some margin. Allthough, it might be the KMC e10 EPT is the true winner.
