Hello everybody,
Chain wear related question: I understand how chain stretch can contribute to wearing out other drivetrain elements (cassettes, chainrings, etc). What I don’t understand is why different speed chains are ripe for replacement when they reach different stretch% thresholds. E.g. why is a 12 speed chain supposed to be replaced already at 0.5% stretch, while a 6/7/8 speed chain can wait until it reaches 1% stretch?
Cheerios.
by AltruisticMist142
6 Comments
More gears means more precision in shifting.
More worn chains have more ‘slop’ side to side so shifting suffers more on a higher speed system than a low speed one
Higher speed drivetrains are more precise and have a smaller optimal performance range.
Also, the cost of cassettes and chainrings have increased significantly with higher speed drivetrains (along with shift performance tbf), so it makes sense to replace a relatively cheap chain more often to save west on the more expensive parts.
Singlespeed chains are wider and basically indestructible. I have put 20,000 miles on a 1/8″ chain.
I always wait until .75 on my 11 speed seemingly without and premature wear in my other drivetrain components. Does anyone else experience this?
Tighter tolerances are necessary for more gears
Several factors come into play, including the width of the links and the chain line.
For example, on a single speed or fixie, the chain is wide (1/8 inch) and the chain line is perfectly straight. The contact surface between the pins, the bushing and the teeth of the gear are important. Pressure will be distributed over a larger area and wear will be slower on the sprockets and the chain. The chain has not to change gear, so it can tolerate more play.
On a 12-speed single chainring, the power to be transmitted will be the same, but the contact surface is much smaller. What’s more, the chain will move on the cassette and the chain line will often be twisted. This means that pressure and wear will be unevenly distributed. With a 12-speed cassette, the slightest shift or play will interfere with gear shifting. As the sprockets and chainring are thinner, they wear out more quickly. Manufacturers have therefore reduced the maximum acceptable stretch. To prevent excessive wear on the cassette and chainring.
It is important to understand that the pressure is not distributed equally over the teeth of a gear, but that the majority of the power is transmitted by the first two or three teeth engaged, and that this ratio decreases as the chain wears. On a worn chain, the first tooth engaged transmits all the force. When all the power goes to a single tooth, it becomes difficult to change gear.