What's the difference between chain and shaft drive on a bike?
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Motorcycles transfer their engine power to the rear wheel most commonly via a chain or driveshaft. So what are the practical differences?
The chain drive utilises two sprockets - one on the output shaft of the transmission at the rear of the engine and one on the rear wheel, with a chain joining the two. It is the most commonly found setup in motorcycles today and has several notable advantages:
- Light weight
- Minimal loss of power
- Final drive ratio adjustable via different sprocket(s)
The minimal loss of power comes through having lightweight components and a small number of surfaces which cause power losses through friction. The adjustable final drive ratio is an important advantage; if you want more revs at lower speeds or a higher potential top speed you can achieve this through changing the number of teeth on the front sprocket, rear sprocket or both. This can involve changing the chain as well. Disadvantages include:
- Chains and sprockets wear out much more often than a shaft drive should
- Mess. Lubricant is flung off at high speed
- Requires regular maintenance - lubrication and tension
Shaft drive in motorcycles involves a driveshaft joining the transmission to the final drive unit, which then transfers the power to the rear wheel via teeth. Advantages include:
- Low maintenance
- No external (messy) lubricant
- Ease of rear wheel removal
- Long life
Maintenance is generally pretty easy on these - change the final drive oil once in a while and put the appropriate (often high moly %) lubricant on the final drive splines whenever the rear wheel is removed. Disadvantages include:
- Heavy compared to sprockets + chain
- Higher power loss
- Final drive unit repair can be difficult if it dies
- Shaft jacking in some bikes
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