Motorcycles: Shaft vs. Chain Drive

Close-up of motorcycle wheel
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Motorcycles traditionally use either a chain or a shaft drive to transfer power from the engine to the rear wheel. Both chain drive and shaft drive motorcycles offer their own sets of advantages and disadvantages, but chain drive motorcycles are by far the most common on the market today. A rare few motorcycles use a belt drive.

Moto Power

The chain drive system is made up of two sprockets, one on the gearbox and one on the rear wheel, that are connected by a chain. In a shaft-driven system, a shaft connects a gear inside the gearbox to another gear inside a hub on the rear wheel. When the engine is sparked, power is transferred along the chain or shaft to the rear wheel, and the bike moves forward. Either system is commonly known as "final drive," as it is the last set of components employed to deliver power to the rear wheel.

Some manufacturers, notably Harley Davidson, have used belt drives on a few of their model line-ups. BMW, Kawasaki, and Suzuki have also experimented with the belt drive system.

Sports vs. Touring Drives

Classic bike enthusiasts looking to purchase their next motorcycle will primarily encounter chain drives in the vast majority of out-and-out sports bikes. But neither chain nor shaft dominate in the touring or sports touring bike market.

Of all the shaft-driven motorcycles ever produced, BMW far outweighs the competition. The company first introduced shaft drives to their models on the R32 in 1923, and since then the shaft drive has been an integral part of their touring bike line-up. The system has proven to be reliable and robust for thousands of miles. Even some of BMW's dual sport—or on-road, off-road—bikes feature shaft drives.

But BMW is the exception, not the rule. Chain drive models still far outnumber shaft drives—although belt drives are gaining in popularity. To understand why, one must first understand the advantages and disadvantages to both.

Chain Drive Pros and Cons

Chain drive systems are lightweight and easy to service, though they do require cleaning and re-tensioning regularly. Because of their design, chain systems also smoothly absorb shock loads from sudden acceleration, sudden braking, or road irregularities. They also contribute to greater fuel economy. Additionally, the final drive ratio can be changed by replacing the chain and sprockets, which makes chain drive motorcycles more versatile and adaptable to the rider's needs.

However, chains and sprockets will wear out faster than shaft drive components, and the chain will eject particles of lubricant like chain grease onto surrounding areas. This means they require more maintenance and cleaning. In harsh environments like off-road use, the chain could stretch and break, and split-pin type links can become dislodged, allowing the chain to come off during use.

Shaft Drive Pros and Cons

Shaft drives are notable for their durability, longevity, and cleanliness. Because the shaft is self-contained, it rarely ever needs maintenance itself—the bike typically only requires regular oil changes to keep it going. Additionally, the shaft system stiffens the swing arm on the rear tire, providing increased handling and stability, while the absence of lubricants means the system runs cleaner than chain drive models.

On the other hand, shaft drive models typically tend to transmit more of the shock absorption to the bike frame and rider, which is especially true when accelerating or decelerating. The shaft system also has a tendency to lock the rear wheel if the down shifts do not match the road speed, which could be dangerous if the rider is not paying attention.

Due to their longer road-life, shaft drive motorcycles are much more expensive to repair and require parts made by their individual manufacturers—so it would be difficult to find a replacement shaft drive in the middle of a cross-country trip if something were to happen. Although shaft-driven bikes may run longer before needing repair, the costs involved when they do need maintenance are more than many buyers are willing to take on.