An Unsettling and Disturbing Guide to Handling, Modifying and Enjoying Your Car...

You brake, the car's nose dips. You accelerate, the nose rises. You turn left or right and you feel your body forced to the outside of the turn. Now that's all weight transfer in action. Pretty simple physics, really, but vital to your understanding as a driver and as a potential car modifier. Understand the physics of cornering and you will be ahead of the pack.

So, what gives? The tyres, usually. When you apply a force in any direction, to accelerate, brake or turn, the tyres are the sorry chumps that do the hard work. Increase vertical force and you decrease grip. So if you are cornering and loading up the outside tyres (let's assume that the car is fairly well balanced and the bodywork is under some control), as you press on into the corner the forces rise. The tyres squirm, the sidewalls flex and the tread is scrubbed sideways. The vertical force will initially maximise your grip as the tyre is forced to meet the road with maximum width, but then the grip will decline. Add heat into the mixture (through friction) and the tyres will dramatically go off.

Hmmm. What happens to the inside wheels, then? Less vertical force on that side, so grip increases. However, not enough to balance what is lost on the outside. In fact many cars will lift an inside tyre or two in a turn, and a tyre suspended in the air doesn't grip at all ;-)

So weight transfer is holding us back, isn't it! What else can we say about it? Well, if you have a tall vehicle (most off-road four-wheel-drives) then you have a high centre of gravity, which is to say your weight transfer will be greater. So you have even less grip. Bit ironic, really, that people buy 'em to feel safe, when they are actually not, ummm, optimum. Of course at lower speeds off-road the four wheel traction makes up for the weight transfer, but on the highway - watch out!