Rocky Mountain Region Porsche Club It's not just the cars, it's the people
By David Rossiter
Note: The article below was written several years ago, after I had discovered that using street tires in high speed driving events could provide unexpected benefits. These benefits are particularly relevant for drivers with 2-3 years of high performance driving experience.
Take your street tires to the track, and you’ll learn a lot from them.
I spent the last driving season on street tires, and significantly improved my driving skills. Though I had previously used competition tires at track driving events, I was attracted by the prospect of some interesting competition in the restricted classes that require stock vehicles and street tires. After a few driving events, I discovered that street tires are very well suited to developing some key high performance driving skills. Other drivers have had similar experiences. Here is how you can learn from your street tires.
Characteristics and Performance of Street Tires
The performance of street tires is more than sufficient for the low levels of positive, negative and lateral acceleration that are encountered in most city and highway driving situations. High performance driving uncovers their limitations.
Street tires are built for longevity and safety in varied road conditions. They have hard rubber, thick treads, and lots of open grooves to remove water. Consequently, street tires have relatively low overall adhesion, especially compared to competition tires, which are made from soft, sticky rubber and have little tread in order to maximize the area of contact with the road.
The hard rubber compound of street tires also makes for a relatively abrupt transition from a rolling state to a sliding state. They give only very subtle warnings before breaking traction.
Low adhesion of street tires makes vehicle balance very critical in high performance situations. Sudden braking or steering inputs are likely to unbalance the car enough to break it loose. Low adhesion also exaggerates the natural handling tendencies of the car. For example, the natural oversteer of a 911 will be magnified on street tires, compared to the same car on competition tires.
The rubber in the thick tread of street tires “squirms”, generating heat. The heavy tread also retains heat, building tire pressure and eventually overheating in high performance situations. This affects adhesion. Street tires adhere poorly when cold, become stickier as they get warmer until they “go away” when they overheat.
It sounds like street tires have severe performance limitations in high performance driving situations. They do. That’s the inevitable result of building tires for durability in difficult and unpredictable street conditions. However, these performance limitations can be turned to your advantage: they actually make it easier to learn some important aspects of high performance driving.
In high performance driving, most of our learning takes place at the limits of our skills. The goal is to extend those limits.
Lower adhesion of street tires means that you will reach your car’s limits (and yours) at a slower absolute speed than you would with competition tires. Clearly, it is easier to learn new skills when you slow down the action. This applies to learning high performance driving skills just as it does to learning to play a new song on the piano or learning a new tennis stroke. The slower pace makes it easier for us to recognize the exact nature of our performance limits, to explore and refine new skills, and eventually to extend our performance limits.
What Can You Learn from Street Tires?
The specific performance limitations of street tires facilitate learning certain driving skills. For example, street tires can help you become more sensitive to small changes in vehicle balance and how these changes affect your car’s adhesion to the track.
You will learn a great deal about your car’s transition from a rolling state to a sliding state. You’ll become much more aware of how this transition happens at each end of the car and in different situations. You’ll learn to recognize the signs that tires are approaching their limit of adhesion, and you’ll become better able to anticipate the transition.
Equally important, you’ll increase your ability to control and use the rolling/sliding transition. You’ll be better able to manage lateral acceleration, to rotate the vehicle in a turn, and to steer with the throttle.
You’ll also improve your ability to use the brakes at their threshold of adhesion. Street tires brake pretty well in a straight line, but trail braking (braking and turning at the same time) requires a very sensitive touch. A few hours of track time on street tires will give you that touch.
You’ll become aware of variations in tire adhesion that result from changes in tire temperatures and pressures. That awareness will stand you in good stead someday should you ever damage a tire while driving.
The sensitivity of street tires will help you learn to manage the particular handling characteristics of your car. You’ll learn exactly how and when your car starts to break traction, and how to modify that by changing tire pressures, taking different lines through turns, or adjusting braking, steering and throttle inputs.
Improving your management of the rolling/sliding transition also means that you’ll get better at recovering control when your car starts to act like it has a mind of its own. These situations can be very exciting, even scary; things seems to happen very quickly. Street tires will help you build the correct habits — which are sometimes counter-intuitional — that will enable you to react instantly when the situation demands. These are important skills, and it’s very nice to feel some confidence in your recovery skills for those times when you push it a bit too far.
Benefits
Street tires provide some surprisingly good opportunities for improving your driving skills. If you eventually move to competition tires, you’ll be much better able to manage their high performance characteristics if you have taken advantage of the learning benefits of street tires.
Street tires make economic sense as well. Using street tires at the track will save you the expense of additional wheels and competition tires. And you’ll avoid the hassle of changing all four tires before and after each event.
But the most important benefit may be that everything you learn on street tires is directly applicable and transferable to everyday driving situations on the street or highway. When faced with a challenging situation on the road, you’ll know exactly how — and how far — to push the performance capabilities of your car.
