Chain Wear

Almost all new bikes come with o-ring chains. There is no reason to use anything but an o-ring chain on a street bike. The only proper place for an old fashoned non-o-ring chain is on a race bike. Conventional chains have slightly less friction than an o-ring chain - that's why raccers use them.

As the rear sprocket rotates the next chain roller to be fed onto the bottom of the rear sprocket approaches the next groove in the sprocket and it drops straight into the groove. The roller will touch the bottom machined into the sprocket at exactly the same time it touches the wall. The chain roller does not rotate as it enters the groove because it is exactly above the center of the groove. As the engine pulls the chain around, additional rollers are added at the bottom and pulled off at the top. Since the distance between centers of all the pins of the chain is exactly the same as the distance between centers of all the sprocket grooves all the rollers will drop in and pull out without the roller spining. This also means that the engine force that pulls on the chain is uniformly distributed among all the rollers that are on the sprocket at any given time.

This perfect world will last about one revolution of the wheel. As the chain flexes from straight to curved around the sprockets and back to straight, the chain's pins rotate slightly inside the bushing which is inside the roller. Every movement of the pin relative to the bushing when the chain is under tension (i.e. the engine is pulling the chain) wears away some of the metal on the pin and bushing. How much metal is worn away depends on the amount of of lubrication on the chain pin, the magnitude of the tension on the chain and how close the distance between centers of the chain pins matches the sprocket. The greater the mismatch, the more of the pulling force is concentrated on the pin and roller just ready to be pulled off the rear sprocket as the wheel turns.

When a chain wears, 99% of the wear takes place in the pin that goes through the side plates and the the bushing that the pin rides on inside the roller. As the chain gets worn the pin's diameter is reduced and the inside diameter of the bushing gets larger.

If you don't want to put up with all this chain maintenance crap, buy a bike with a shaft drive or a belt drive. One word of caution on drive belts, they work fine and last a long time but they are susceptable to little pices of stone getting stuck in the rear drive pulley teeth. This doesn't happen to chains because the sprocket teeth are too big and the wrong shape to catch a stone but a belt's rear pulley teeth are just the right size to catch a small stone and if one does get stuck it can trash the belt in no time (like hours). If you ride a belt drive bike on gravel roads check the rear pulley for stuck stones as soon as possible after you are back on the pavement. Also, if you have one of the few japanese made belt drive bikes you will probably have a hell of a time finding a replacement belt if yours breaks on the road. Harleys should be no problem as that's all they make now plus they almost never break unless a stone gets stuck in the rear pulley.