It's ironic how little the average consumer, or even a car nut knows about tires even though everyone has a set, it's the most important aspect of any car and plays the biggest role in performance. All too often, tires are picked purely on price. Those who claim to know a little about tires might consider grip, but that's not even the tip of the iceberg when it comes to the tire. In this series, we teamed up with various tire manufactures, tire engineers, and racers to gain some insight into the mysteries of the tire, what it's supposed to do, how to pick a set, and most importantly how to extract its maximum performance.
First and foremost, let's get one thing straight, the only part of the vehicle that keeps the driver in touch with the ground are those four little black doughnuts. And they aren't just round, black, and made of rubber. Tires are arguably the most complicated and useful device that man has produced. It's probably the most underrated for that matter, even though tire companies spend untold millions of dollars each year designing, developing, testing, and optimizing the tire. Even though, as tuners, we can never hope to re-engineer or build different tires for our performance needs, like we do with suspensions and engines, selecting the proper tire is still absolutely the most critical factor. It's so important that any tire manufacturer of relevance will have an entire team of engineers strictly devoted to helping racing teams select and dial in a set of tires. But first, you have to understand the tire in order to properly select one for your needs.
What a tire is and what it's supposed to do
A tire is not just a rubber hoop made by pouring liquid rubber into a tire-shaped mold. It's as complex as your body with specialized structures in different areas for strength, flexibility, and resistance to wear and heat and the huge forces constantly acting on it. What makes it so amazing is the juggling act of roles that it has to fulfill. A tire has to provide grip while lasting as long as possible, communicate the road to the driver while providing a comfortable ride, provide traction in opposing conditions while minimizing noise. On top of that it has to be affordable for a huge range of customers with different needs and applications.
In its simplest form, a tire is essentially a pressure vessel with several primary functions. The most obvious is to provide an interface and interaction between the vehicle and the roadway. The tire's contact patch, or foot print, for the average vehicle today is less than roughly the size of an average male's hand. These four small contact patches are the only things that translate accelerating, handling, and braking from the 3,000 pounds of steel into the asphalt.
The ability to accelerate, brake, and corner is solely dependent on the friction developed between the interaction of the tread rubber and road. Slick racing tires have the ultimate amount of friction or grip, but cannot operate safely in a weathered environment. Tread designs are developed to deal with the evacuation of water, snow, and mud from the tire contact patch to maintain rubber-to-road contact. The tread is one of the more difficult elements to deal with as the factors involved, dry and wet traction, wear, and low noise, usually conflict in terms of ideal design. It's a balancing act of trade-offs.
This pressure vessel is also required to carry the weight of the vehicle both statically and dynamically. Each tire carries a part of the vehicle load and these loads may change at any given time due to weight transfer.
It would be easy to carry the vehicle's weight if the tire was a rigid structure, like those on fork lifts, but a road tire also has to absorb its share of impacts and road irregularities under a broad range of road conditions. So, another role of the pressure vessel is to have spring and damping abilities.