Motorcycles: Shaft versus Chain Drive

Close-up of motorcycle wheel
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Motorcycles traditionally use either a chain or a shaft drive to take 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.

The chain system utilizes two sprockets, one on the gearbox and one on the rear wheel, connected by a chain while the shaft system uses a shaft to connect a gear inside the gearbox to another gear inside a hub on the rear wheel. Either system is commonly known as "final drive" as it is the last (final) set of components employed to deliver drive to the rear wheel.

Some manufacturers, notably Harley Davidson, have used belt drives on some of their model line-ups, but the vast majority of classic bikes will have chain and sprockets for their final drive. However, when it comes to buying a motorcycle with one of these systems, it really comes down to the rider's preference and the make of bike they're getting.

Chain Drive and Shaft Drive by Motorcycle Types

For classic bike enthusiasts looking to purchase their next motorcycle, the choice of either a chain or shaft drive will come under consideration. If the bike is an out-and-out sports bike, the choice will be limited primarily to chain drive; however, if touring or sports touring is the intended use, the choice will be much broader.

Of all the shaft-drive motorcycles ever produced, BMW has by far produced the greatest number with their boxer twins — 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 (on-road, off-road) bikes feature shaft drives — however, the chain drive motorcycle model is still produced in larger quantities than shaft drive models are. To understand why, one must first understand the advantages and disadvantages to both.

Advantages and Disadvantages of Chain Drive Motorcycles

The chain drive system comes with a variety of benefits and issues to owning this style of motorcycle, but according to the current market, the advantages outweigh the disadvantages for chain drive bikes, so more are produced than any other type — though belt drive motorcycles are edging in on the market.

Chain drive systems are light weight 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, braking or road irregularities and provide better fuel economy for the bikes that are using them. Additionally, the final drive ratio can be changed by replacing the chain and sprockets — so this 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 (chain grease) onto surrounding areas, making them require more maintenance and cleaning as well. 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.

Advantages and Disadvantages of Shaft Drive Motorcycles

The strong design of shaft drive bikes offers their greatest advantages: 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.

Shaft drive models are currently undergoing heavy construction and the designs typically tend to transmit more of the shock absorption to the bike frame and rider, which is especially true for the torque reaction from 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, leading to dangerous scenarios while on a two-wheeled vehicle.

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 they may go longer before needing repair, these bikes' associated costs dissuade many buyers from owning them.