The Computer Chip in Your Butt

A while back, an article in Racecar Engineering Magazine discussed the effects of “self-aligning torque” on the driving task. Self-Aligning Torque is the amount of effort or force needed to move the steering wheel. It is measured in pounds and is the vehicle’s way of communicating to the driver that everything is cool, no worries, or that in a few tenths of seconds, you and the principal will be experiencing a lot of excitement.

The article mentions that when a vehicle is approaching its limit of adhesion, a driver has two conflicting signals. The first signal is the steering wheel getting light, which means that it requires less effort to increase steering input (turn the steering wheel). The reason for this is that the adhesion the tire makes with the road is getting increasingly smaller – quickly.

The second signal is the vehicle load the driver feels at the back of the seat (their butt), which at the limit of adhesion is high.

Therefore, at a critical decision-making moment for the driver, the computer chip in their butt is telling them one thing: high energy is pulsing through their body, and their hands are feeling little to no steering response. And to make life more interesting, all this is happening in tenths of seconds.

The Racecar Engineering article goes on to say that this can create a conflict with even the most experienced race car driver. The article points out that a good driver (Security Driver) has to be able to separate the two conflicting signals.

Race car drivers who get paid a significant amount of money use computers to sort all these out, and it is the primary reason why computers should be used in driver training.

Self-Aligning Torque (SAT) is a “learning experience” that needs to be created and coached. Also, in my opinion, a good instructor knows the speed that SAT will occur in any given exercise.

The difference between good instructors and great instructors is that great instructors understand the implications that the science of vehicle dynamics has on the task of driving in general, and also specifically on the exercise/scenario that the student is maneuvering through.


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