DRIVER DEVELOPMENT: Car Control
Braking late, hitting apexes, and powering out of corners: The goal of driving a car quickly requires keeping the tires at their limit at all times. Having good car control is a crucial skill in the development of a driver to not only drive a car fast, but also to have the ability to get up to speed quickly in a new car and on new tracks. However, without self control and discipline, having good car control can actually work against you.
For those of you who don’t know me, my name is Billy Johnson. I have raced professionally for over 15 years now and have raced everything from the 24 Hours of LeMans for Ford to the NASCAR Cup series for Richard Petty. I coach everyone from beginners who are just getting in to track days, to mentoring and advising young aspiring racecar drivers, to business executives, actors, and professional drivers in different disciplines from NASCAR to rally racing. The following article is a result of what I have learned in over a decade of racing cars ranging from spec Miatas to prototypes and stock cars, and from instructing drivers in all of these fields with various backgrounds and driving disciplines.
This is going to be a long, in-depth analysis of driver development. I may lose some folks right off the bat, however if you are seriously interested in improving your driving craft and want to understand where you are as a driver, it is worth hanging in there. Whether you are a beginner or a pro, I hope the following information helps you on your quest to become an even better driver. Now on to the article.
During the development of a driver, learning to approach – and mastering the craft of balancing the car at the limit of grip is the name of the game. Having the comfort and confidence (or lack thereof) greatly affects the process of learning and the ability to execute driving a car fast. To simplify things I will separate the car control abilities of drivers into three categories: Under developed, Over developed, and Refined. However, before talking about these three types of drivers, we first need to get a crash course on understanding how tires behave.
We could talk about tire deflection, aligning torque, mechanical and pneumatic trail, tire load sensitivity and a bunch of technical details of how a tire works, but for driving purposes we will focus on themes and abstract concepts related to driving without getting too far off on a technical tangent.
First off we need to be aware that “SLIP ANGLE” and “YAW ANGLE” are different. Generally speaking, SLIP ANGLE refers to the difference between the direction the tires are aiming and the path that they actually take. For example, if a car encounters a heavy cross wind, the force pushing on the side of the car will cause its path to change even though the steering wheel is held straight. This happens because the crosswind generates a slip angle on all four tires which is different from where the steering is pointed, causing the heading to change. When cornering, tires will always generate a slip angle regardless if the car is pushing off the track while understeering, sliding the rear tires while oversteering, balanced through a corner, or simply turning the car in a parking lot at 5mph.
The yaw angle of a car refers to the difference (in degrees) between where the centerline of the vehicle is aiming, and the actual path the vehicle is traveling.
YAW ANGLE refers to the difference from where the front of the car is pointed and the path that the car is traveling in. In drifting, an important judging criteria is how large of a yaw angle a car can achieve. In some cases the car can be perpendicular (90-degree yaw angle) or even slightly past perpendicular from the direction it is traveling. Yaw angle is somewhat of a separate but related concept from slip angle. For example: If a car hits a patch of ice and the driver adds full steering lock, the front tires could have significant front slip angles, zero rear slip angle, and zero yaw and the whole car would just go straight. Likewise, a car that is drifting could have significant yaw (sideways) and rear tire slip angles, but a much lower front tire slip angle since the front tires are not sliding very much and controlling where the front of the car is heading. When we discuss slip angles, we are talking about the deflection at the tire and not the yaw angle of a car during over or understeer.
10 comments
Great article! Had to follow up here after the Speed Secrets weekly left me hanging on the definition of the refined driver!
Thanks for listening in and reading this here!
I have been using a simulator to get more comfortable with driving beyond the limit. On track, as soon as the problem occurs, I generally have the developed muscle memory necessary to get out of the trouble I created. It replaced some of the other questionable methods I used to cut my teeth as a younger adult.
Like Ernie (above), I found this article after reading Ross’s latest Speed Secrets Weekly. I am a club racer, and tend to be very timid about losing control of the car by going past the limit. I took a one day Car Control Clinic at Lime Rock earlier this year, and developed some confidence in going over the limit at low speeds. But at higher speeds, on a dry, fast track, it is still a struggle. I will be driving at Thompson in CT next month, that has some slow corners with wide runoff. I’ll drive on worn out tires, and force myself to do some sliding!
Great article Billy. I have been driving at HPDE’s for 3 years now and agree with what you say. I’ve had some instuctors push me past my current limits and helped me get faster only to come back to the same track and have an instructor slow me down and not let me drive to my current abilities.
Thank you for such detail in the article. I have found my place as a driver just by reading this. Now I can focus on the next area of improvement for myself.
I absolutely enjoyed reading this. This is exactly the Aviation-level, in depth ground school that teaches you how to think about what you’re doing. -And how to understand reality for what it is. I know this will provide a solid foundation for my first HPDE event later this year. Thank you.
Thank you for the feedback, I am glad to hear it!
Wow! What a great read. Thank you for taking the time to explain this in all the detail that you did! I know where I am behind the wheel and where I wish to go. This article was exceptional. I can’t wait to gain more seat time and practice car control more and more!
Excellent article, Billy! Looking forward to learning more from you. And yes, please continue to write. You have a gift and both a driver and writer!