Today on Tech Time with Mike Smith, I’d like to talk about why weight reduction is so important in a performance vehicle. It is common knowledge that a lighter vehicle will handle better and be able to generate higher peak G-Forces in a turn when compared to an identically prepped car that is heavier. But why is this the case? It seems counter intuitive since you can easily drag a piece of paper across a desk, but then once you put a paper weight on it, it becomes harder to drag. The friction force between the paper and desk increased with the additional load of the paper weight, so the same should happen with your car, right? Well, lucky for us, tires aren’t made of paper, and therein lies the difference in this scenario. Tire dynamics is a very complicated topic, involving adhesion, cohesion, friction, hysteresis among other principals. It is these principals that allow engineers to develop tires capable of producing greater than 1 lateral G without the assistance of aerodynamic components. If a car’s lateral grip was generated only by friction, it would only be possible to generate 1 g of lateral force. Like all complicated things, tires have specific optimal operating parameters; temperature, pressure, slip angle and load just to name a few. With racing tires, it becomes even more important that these parameters are within the optimal operating range, due to the fact that a racing tire’s grip comes mostly from adhesion and cohesion rather than friction. Below is an example of a racing tire’s load vs lateral grip graph. As you can see, the grip increases linearly with load until a certain point, beyond which the amount of grip per unit load begins to fall off. This is something that you can easily test on your own. Go to a skid pad with your car and test it with varying amounts of ballast (keep careful control of other parameters such as tire pressure/temperature and fuel load). Time how long it takes the car to do laps around the skid pad (trying to keep the car tight) with various loads.