by Krzysio on Thu Mar 30, 2023 3:23 pm
I never buy Shimano chains, but I think it's also a riding style that makes a bigger difference in how the chain wears. With today's gear ratios, most cyclists ride with a cadence of around 90rpm. But I know a few, especially older, even experienced cyclists who could not switch to a higher cadence. One of them, who covers 20,000 km a year, rides with a cadence of 53rpm, even though he only rides on flat terrain, steady pace, all the time sitting on the saddle 52/14! He has roughly the same power as me, but he declares that his chains last 60-70% more than mine, even though he washes the chain only once or twice a year, and usually only wipes it and lubricates it with medium-quality lubricant.
I decided to take a closer look at this conundrum, suspecting that his chains would be worn beyond measure, and I took his worn chains: Ultegra 10-speed and Dura Ace 11-speed.
Here's what I discovered first: the chains were almost as short as the new one! The pins were intact, but the rollers had dished tops, and were rolled. I think that this turn of events is partly due to the fact that when riding at such an extremely low cadence, the chain travels about 40% less distance than the distance of the biker's riding at high cadence ( gear ratio difference makes them both to cover same distance with different chain speed ). This slow chain, in turn, determines that the pins at the same time make 40% less movements on the abrasive attacking them. And the rollers crease much more, where the constant pressure needed to turn a hard gear is much greater, than when riding in a soft gear.
The owner of these chains considered them to be worn, because that's what the chain wear indicator showed. However, the indicator does not show whether pins or rollers are worn. Strictly speaking, in this case it showed only the wear of the first and last roller of the measured section, while on a chain with worn pins, the sum of the wear of all pins of the measured section is shown, and then the indicator gives a useful value. At first glance, it seems that the described chain should be suitable for disposal much sooner, than it was, since only 2 worn rollers made gauge already showing 100% wear of the chain. What if you add up the wear of all rollers from between! But this is not the case, because the wear of the rollers - as long as the pins are not worn - does not change the length of the chain, because the pins determine the position of the individual rollers anyway, and more importantly, the position of all chain elements. So, it is wear on the pins, not the rollers, that causes the chain to elongate. And when the rollers are significantly worn, they still fit properly into the valleys between the teeth ( see photo ), until the pins have wear that increases the play of the links. In turn, it is the length of the chain section entwining the chainring (i.e. about 28 links on a large chainring) that determines the threat to the rest of the drivetrain elements from the elongated chain. This is so, because in the new chain the spacing of the links/pins is correlated with the spacing of the teeth, and when the chain gets longer - for example 6mm on 30 links - the chain wraps around the ring, the first roller lies at the bottom of the teeth valley, and the 30th roller is 6 mm too far, i.e. at the tip of the tooth . And destroys it.
When I examined these chains, my city bike's chain was about to be replaced. So I changed it to this Dura Ace with partly damaged rollers ( but still short ) and it still works technically OK, and feel as good as new one rather than mine just worn out. Almost no slack can be pulled on the chainring.
So, in this case, a chain worn by the reading of instrument is still safe to use - for a long time so far - although it probably shouldn't be put on a $10,000 bike at this stage. Especially it's safe to be used by high cadence, not a strongest guy on the planet, to start wearing pins/stop smashing rollers. And that “long time” on my commuter is not particulary long during Polish slush, road salt period to be prcise. In such circumstances pins start disappearing quickly even with Silca Synergetic lube.
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