Chains vs belts. Who wins the fight?

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Star Raider Reliably Puts Big Torque Through a Relatively Narrow Belt

None of this suggests that chains will disappear anytime soon. For one thing, chain can wrap around smaller sprockets than can belt. Chain will happily embrace chain wheels down at about 3-inches in diameter, whereas belts need pulley diameters of at least 4.5-inches if they are not to begin feeling distressed. And because the countershaft pulley is big, so must the wheel pulley enlarge in order to get the appropriate final-drive ratio. Some people may not like the appearance of a big belt pulley on the rear wheel. Chains are narrower than belts too, and because they straddle the sprockets, produce a pretty narrow total package.

There have been pretty impressive improvements in chain technology, as well. Improved metallurgy has led to higher tensile strengths, while modern manufacturing processes have improved tolerances and assembly techniques. The biggest bugaboo with chains is that they are not flexible. Instead, individual links are allowed to pivot on bushings at both ends of every link. The challenge has been to defeat the wear that occurs at the moving elements that allows longitudinal play. The play permits the chain to stretch beyond its operating limits, to the point where its combined link pitch no longer matches that of the polygonal sprockets on which it rides.

Efficient lubrication reduces the wear, but external oiling can only go so far in mitigating bushing wear, so manufacturers came up with the clever idea of packing grease inside the bushings, and then sealing the end plates (which move in relation to each other) with O-rings. That dramatically increased the service life of chains, but we soon found that the O-rings were susceptible to wear and environmental attack from aggressive cleaning materials or from the solvents in inappropriate lubricants.

But most consumers have caught on now, and ensure that chain lube containers indicate the formulation is suitable for use with rubber O-rings. Now we are seeing variations on the O-ring theme, with X-rings that offer multiple lubrication pools and seal points, and from chain manufacturer RK Chains, a novel new twist called the XW-ring.

This page from the manufacturer's website probably explains it more clearly than we could. Note that the text here contains RK's claims, unverified by MD

Obviously, chain manufacturers are not about to give up their huge involvement with motorcycles. Nor should they. But it's nice to see an alternative to the noise and mess of chains, and the extra unsprung weight of shaft drive. Right now, belt-drive has made huge inroads into the cruiser market. The big question is how far the technology may penetrate the rest of the motorcycle model spread. It's going to be an interesting tug-of-war.

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