A quick stroll around the showroom this afternoon reminded me of something that I’m aware of but which seldom warrants much thought. It’s this. Our inventory includes multiple examples of each of today’s common forms of motorcycle drive system – shaft, belt, and the ever-popular chain. So, what’s up with all this diversity? Can’t the industry just figure out what’s the best system and go with that? Apparently not as some recently introduced, and high profile, new products are arriving in each configuration. Yamaha Star “Bolt” – Belt. Triumph Tiger Explorer, Trophy SE, and Suzuki M50 Boulevard – shaft. Kawasaki ZX6-R and Ninja 300 – chain. Maybe you have a favorite of your own. In any case let’s review some of the pros and cons of each of these systems.
Shafties are up first. Beloved by BMW, who have made literally millions of shaft drive bikes equipped with their iconic “Boxer” engines, shaft drive offers a strong, clean, and durable (most of the time – BMW riders with final drive issues feel free to weigh in here) system. In addition to BMW, we find shaft drive on some Triumphs as well as a number of the bigger displacement metric cruisers. No cleaning and repeated lubrication is required. Also, shaft drive is often combined with a single-sided swing arm making those rear wheel/tire changes simple. On the other hand, they tend to be heavy, expensive/difficult to repair, and if you thought you’d like to make a simple gear ratio change like you can do with your chain drive bike, then think again. Needless to say, shaft drive is also relatively expensive to manufacture which leads to their application only at the high end of the market. But, if you’re leaving tomorrow for Magadan in Russia (look it up) and don’t want to mess with lube, cleaning, sprocket wear and the like then shaft drive might be a good choice.
The application of belt drive has grown a great deal in the past couple of decades. This actually represents the return of a technology that was common early in the 20th century and at the dawn of motorcycling. At that time leather drive belts, like those use to drive machine tools like lathes and such, were all the rage! A major belt proponent is Harley Davidson, users of belts for virtually every current application. In it’s current manifestation, belt drive is typically a toothed belt (“Gilmer” belt) running between hard anodized pulleys. It’s quiet, absorbs shock well and doesn’t require routine maintenance. On the other hand belts have a finite life and will have to be replaced on schedule much like the similar belts that probably spin the camshafts on your car. They are also less than tolerant of the ingestion of rocks and such – lending them distinctly unappealing to the off road crowd.
Now we arrive at that hardy perennial, the chain drive. Proponents (of which there are many) point to the fact that chains are light, take up little space, are mechanically very efficient, and are inexpensive. These are attributes of great appeal to manufacturers. If you are so-inclined it’s also quick and easy to change ratios. On the other hand chains require very regular maintenance – cleaning and lube mostly. But the chain lube can be messy – tossed off the spinning chain onto the wheel, bodywork, and occasionally the rider’s leg. This behavior has spawned a legion of special clean-up tools and materials. Chains also demand regular tension adjustment. This is, admittedly, a simple operation requiring common hand tools but it must be looked after nonetheless, lest you toss a chain off and find yourself motionless at the side of the road. Or worse. Chains and sprockets are also “finite life” items. Your bike and engine may be fundamentally durable for tens, even hundreds, of thousands of miles but the chain and sprockets are substantially less so. Do a meticulous job of cleaning and maintaining your chain and it will probably last 20,000 miles or more. Ignore it and life will be significantly reduced. Products like the ScottOiler, which do a real-time job of lubrication, can help on this front. Chains remain the most common of motorcycle drive systems.
So there you have today’s three most common motorcycle drive systems. Each has it’s proponents and it’s detractors. Maybe you have an opinion on which is best. If so, why don’t you share and make a comment here!