anyone know the benifits of lightweight wheels?

[eTiMaGo]

Man, I need to find my old physics textbooks

Back on the original topic, I find it easier to explain these phenomena with basic everyday examples...

Effect of total car weight

Imagine you're at the supermarket. How much easier is it to push the trolley around when it is empty compared to when it is full? It's a lot easier to speed up, stop, and turn when you have less weight.

Effect of wheel weight (or pulley, or any rotating mass)

Imagine you have two tops (spinning tops, what kids used to play with long ago...), a heavy one and a lighter one. Think of how much extra twisting force you have to give the heavy one to get it to spin at the same speed as the lighter one. It will also keep spinning longer, and if you try to stop it by hand, you will need more stength to do so.

Also, imagine you are riding a bicycle, and you want to go up a low curb or something similar. You'd usually slow down, because when you go fast, the inertia of the wheel (the same force that lets your bike stay upright instead of falling over, when you are moving), will want to drive the bike straight through the curb, instead of up and over it. In car terms, the lighter the wheel, the less inertia it has, and the easier the suspension can react to bumps at higher speeds.

In reality there is always a compromise somewhere... smaller lighter wheels will help with response, but that means running a taller sidewall which can flex and make the handling less precise.

Also, something I've been pondering, the Yaris is quite tall and kinda top-heavy, so heavier wheels may be an advantage in stabilizing the car, shifting the center of gravity down a bit, keeping the car a bit more planted at speed? This would only be really useful on a highway, but just something that might be worth to consider.

Anyway, I hope that helped, for the less technically-minded out there