In my last post I mentioned how you can make a forged wheel light and strong. So why is this important?

Basically a wheel/tire/brake system is called the unsprung mass of a vehicle. The sprung mass is the body, the engine, the passengers and everything else that is supported by the suspension. Now you’ve probably heard about minimizing the unsprung mass, right? Why is this important? Well remember your high school physics class? F=Ma… Force = Mass x Acceleration. The higher the unsprung mass, the more force exerted on the sprung mass and this is what affects handling and ride comfort. The higher the force exerted on the spring of the suspension, the higher the force required to keep the wheel planted to the ground and this is what affects handling. That same force is also reacted by the sprung mass (body of the car) and so the passenger in the vehicle feels that force and its effect on ride comfort. The higher the force, the worse the ride comfort. Basically you want wheels to lightly move over bumps in the road or track and the lighter the wheel, the lower the forces involved. This is a pretty simplified explanation but I hope it gets the point across.

But that’s not all. The unsprung mass also has an effect on the vehicle’s acceleration and deceleration. Well… of course it does because F=ma, right? So the heavier the wheel, the slower you go. Well that’s only part of the story. The other part is called rotational inertia and it has much more of an effect than that shown by the linear relationship of F=ma. That’ll be the topic of my next post.