The Weird Science of Racing Tires

Before I started racing, I don't think I understood how complicated tires were. They were just the four things connecting a car to the road. Now they're one of the things I think about constantly when I'm in the car.

Racing tires behave very differently from the tires on a normal road car, and sometimes in ways that seem completely backwards. For example, a dry-weather racing tire is usually "slick," meaning it has basically no tread at all. That would be a terrible idea on your everyday car, especially if it started raining, but on a dry racetrack the smooth surface means more rubber can make contact with the ground, which creates more grip.

Then there's temperature. Racing tires have a certain operating window where they perform best, and getting them into that window can make a huge difference. That's one reason you'll sometimes see drivers weaving back and forth behind a safety car or during a formation lap. It might look like we're impatient, but we're trying to manage the temperature of the tires before we need them to perform. Too cold and you don't have enough grip. Too hot and they can start degrading quickly. And, unfortunately, there isn't a little temperature setting in the car where you can just choose exactly what you want.

Weather makes the whole thing even more complicated. Slick tires are great when the track is dry, but once enough water gets onto the surface, they become a problem very quickly. Wet weather tires have grooves designed to move water away from the contact patch and help the tire stay connected to the track instead of sliding across the water. That's why a sudden rain shower can completely change a race. Sometimes the most important decision isn't how fast you're driving, but whether you're on the right tire at the right time.

Tires also change throughout a race. Every braking zone, acceleration, lockup, curb and corner puts stress through them. If you lock a wheel badly enough, you can even create a "flat spot," where one section of the tire gets worn down more than the rest. You usually know pretty quickly when you've done it because the car starts vibrating every time that section rotates back onto the track. Not exactly ideal.

Then there's tire degradation, which adds an entire strategy element. Driving as fast as possible every single lap isn't always the fastest way to finish a race. If you overwork the tires early, you might be much slower later. Sometimes you have to give up a little performance now so that you still have something left ten laps from now.

That's probably the part I find most interesting. Four pieces of rubber can affect almost every part of a race: setup, strategy, weather decisions, pit stops and how aggressively a driver can push.

People tend to notice the engine or the aerodynamics of a race car first because those are more exciting to talk about. But none of it really matters if you can't transfer that performance to the ground.

And all that's connecting you to it is an area of rubber roughly the size of four hands.