There is no perfect drive system. Let us take a look at the options.
Having had shaft driven bikes and knowing the joy that they can bring for their clean, hassle-free longevity, I fully understand how well respected they are. They rarely require maintenance and have the additional benefit of the shaft system inherently stiffening up the swing arm, which increases stability and handling for a well planted feel. It is easy to understand the appeal of shaft driven bikes to so many people and I have to say, I have never had a mechanical problem with one and the last one I owned was on a 43 year old R80/7.
However, the dark side of the shaft drive is that they are heavy and tend to transmit more of the terrain’s shocks up through the bike. The shaft costs the bike up to 25% of power transferred to the rear wheel, and power costs mean fuel costs too, and this power transferred in to the shaft system also creates run on momentum on deceleration.
Having formerly been a mechanical engineer and having trained at the country’s leading motorcycle engineering college in London, should the unlikely event of a shaft drive fail beneath me on the road I would instantly know that a roadside repair would be very unlikely. It would probably require expensive specialist parts that would take time to get, depending on my location!
The belt drive sits in the middle of the chain and shaft, working very much like a chain drive but with a Kevlar composite belt and pulley(s) instead of a chain and sprockets, the ride is smooth and quiet with the belt requiring very little attention.
The downside to the belt is limited customization and they are not suitable for rough stony roads and tracks and they suffer up to 15% power loss during the transmission process.
The chain drive is my personal favorite, albeit a love hate relationship! I hate the needy attention it requires, but love better power and fuel economy and the fact that I can change the final drive ratio at the sprockets, adapting them for my needs as I sacrifice little top end for more acceleration.
They are lightweight, begrudgingly easy to service, but very reliable if serviced properly. The chain drive helps smooth out shock loads from irregularities on rough roads and the trusty old chain and sprockets can hold its head up high as the most efficient final drive with only up to 4% transmission loss.
The downside of the chain and sprockets arrangement is that they wear out quicker, they are dirty, require more maintenance and cleaning of the surrounding areas as the chain spits its excess oil over your bike, and if not maintained properly the chain drive can stretch excessively, become derailed or even snap.
What drive works best for you?