Most motorcycles of today are driven by a pair of sprockets connected through a chain. This is the most common type of final drive, but it's not the only one. Belt and shaft drives are the two other final drive systems and they can be found on some of the latest motorcycles. For example, Harley-Davidson and Indian motorcycles love using belt drives on their cruisers, while BMW loves to add a shaft drive on many of their latest models. So what are the pros and cons of each of these final drive systems? Let's dive in to find out!
Chains are made by a series of plain bearings linked together by inner and outer plates. Two sprockets, one on the gearbox and the other on the rear wheel, are used to drive them.
Chains are compact, easy to replace and durable. They also offer the most efficient transmitting of power with only 3% transmission lost. Chains are the cheapest to make which is also a reason why they are the most popular.
One of the biggest cons of chains is that they require a lot of maintenance. They need to be cleaned and lubed frequently. You’ll also have to replace the chain and sprockets regularly which can be a pain to some folks. Chains are also known to not run as smoothly or as quiet as belt or shaft driven motorcycles.
Belt drives are built similar to chain drives. Belts are made of a strong rubber-like synthetic material that has teeth or grooves on the inner side. Two pulleys, one on the gearbox’s output shaft and another on the rear wheel, are used to drive power.
Belts run very smoothly and are quiet. They also are very low maintenance. While motorcycle chains need to be cleaned and lubed often to last, a belt can easily last between 15,000 to 20,000 miles without being touched.
Belts are great but they do have their share of cons. One of the biggest would be that they are more prone to damage. If you’re out for a ride and manage to get a pebble stuck in one of the pulleys, it will cause the belt to wear down quickly. Belts are also more expensive to replace than any chain would be so this can become an issue. Belts also don’t deliver power quite as efficiently as chains as the power loss is close to 11%.
The strongest final drive available is definitely a shaft drive. This final drive system consists of a shaft that’s connected to the gearbox output through a universal joint. The shaft is connected to the rear wheel through a spiral bevel gear. The bevel gear turns the direction of rotation of the shaft by 90 degrees to make the wheel turn. This entire drive system is bathed in oil for lubrication and sealed to protect it from any external elements. Pretty complex!
Shaft drives are complex to explain, but easy to maintain. They actually hardly ever need any maintenance and can last the entire lifetime of the motorcycle. Shaft drives also run a lot smoother than any belt or chain would ever.
Shaft drives are heavy and require a lot more power from a motorcycle engine. With so many moving parts, these are known to lose up to 31% of power through the process. Also it’s a lot more expensive to replace any parts inside of a shaft drive if it fails.
Like most things in life, each of these final drives share their advantages and disadvantages. Hopefully I've provided enough insight on the topic! Next time you head to your local dealership try and see how many belt or shaft bikes you can spot!