To take drive from the engine to the rear wheel, motorcycles have, for the most part, used either a chain or a shaft since their invention. The chain system utilizes two sprockets, one on the gearbox and one on the rear wheel, connected by a chain.
The shaft drive 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.
Chain Drive and Shaft Drive by Motorcycle Types
For classic bike enthusiasts looking to purchase their next bike, the choice of either a chain or shaft drive will come under consideration. If the bike is an out-an-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 greater.
Of all the shaft drive motorcycles ever produced, BMW has by far produced the greatest number on their boxer twins. The company first introduced shaft drives to their models on the R32 in 1923. 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.
But what are the advantages and disadvantages of each system?
Chain Drive Pros and Cons
- Light weight
- Easy to service (requires cleaning and retensioning)
- Smoothly absorbs shock loads from sudden acceleration, braking or road irregularities
- Final drive ratio can be changed by replacing the chain and sprockets
- Better fuel economy
- Chain and sprockets will wear faster than shaft drive components
- Chain will eject particles of lubricant (chain grease) onto surrounding parts
- Chain will stretch and break in harsh environments (off road use in particular)
- Split-pin type links can become dislodged allowing the chain to come off
- Requires regular cleaning and service (tension and lubrication)
- More difficult to change rear tires (double sided swing arm types)
Shaft Drive Pros and Cons
- Strong design ensures longevity
- Low maintenance (oil change only)
- Stiffens the swing arm
- Cleaner than a chain
- Facilitates rear wheel removal
- Heavy construction
- Early designs tended to transmit shocks to the rider
- Tendency to lock the rear wheel if down shifts did not match road speed
- Torque reaction can be felt by the rider (bike may tip to one side during acceleration or deceleration)
- Expensive to repair
For most classic bike riders, the final drive system will match their bike choice. Enthusiasts looking to purchase their first classic must consider the likely use of the machine.