Motorcycle Unsprung and Sprung Weight
Heading out for a motorcycle ride means enjoying the adventure
You’ve already noticed that motorcycles, unlike auto-mobiles need special additional
Shimmy, speed wobble, tank-slapper or head-shake – all names used
Part of travelling so smoothly and keeping the your motorcycle on the ground has to do with the components that make up the “unsprung and sprung” weight on your motorcycle or scooter. It’s also known as unsprung and sprung “mass”; the opposite of which is a motorcycle’s “sprung” mass.
Unsprung Weight is A Collection of Components
So speaking of unsprung weight, this includes the collection of motorcycle components such as your rims, wheel axles, brakes / callipers, tires, and a portion of the weight and suspension links. Unsprung weight is largely a function of the design of a vehicle’s suspension and the materials used in the construction of suspension components.
This combined mass is one of the most critical factors affecting your motorcycle’s road holding ability. As unsprung weight is that portion of your motorcycle not supported by the suspension it is the most susceptible to road shock and cornering forces.
To make your steering and handling performance easier, it’s as simple as reducing unsprung weight. One way is to exchange your steel rims for lightweight (but pricey), aluminium, or state of the art, carbon fibre rims. These will allow you more precise steering inputs and improved “turning in” characteristics—plus look incredibly sexy on your bike!
Simple weight reduction by way of wheels, is a key concept that many riders overlook—but you probably noticed more and more, that today’s motorcycle models are arriving from the factory with lighter weight wheels. Ducati’s a good example of this using the famed Italian brand Marchesini for most sport/ super-bike models.
Effortless Better Handling
So, here’s what really happens to the unsprung mass. When you ride over bumps and surface imperfections in the road, these cause tire compression, which induces a force on the unsprung weight. Every time you hit a bump, the wheel assembly is accelerated upwards, decelerates to a stop, and then accelerates downward until it reaches equilibrium. If the wheel can’t accelerate fast enough, shock is transmitted to the body, which may upset the balance of the bike.
The whole idea for better handling is to reduce unsprung weight because you’ll minimize the load placed on controlling the motion of the wheels and tires. This means that suspension springs and shock absorbers will have a greater reserve capacity to control body motion; just as they were intended to!
The result is effortless better handling. Plus there’s a lower rotational inertia resulting in a quicker and more responsive steering, meaning less driver/ rider fatigue.
A definite for your motorcycle “must do” list during off-season motorbike works.