You’re driving down a slick Wyoming highway on a cold winter’s day, when all of a sudden a deer darts out right in front of you! Your automatic response? You slam on your breaks. What you probably didn’t anticipate was spinning out of control and beginning to travel in the reverse direction. This leads to several important questions; why did your particular car begin to spin out? What are the physics behind this spin and how can you regain control?
Spins, or skids occur when your tires lose friction with the surface of the road, without friction its easy to lose control of your vehicle. There are two very probable causes as to why your car began to spin and travel in reverse due to your hard braking. First of all, you most likely have a front mounted engine. This means that your rear wheels carry less weight than your front two wheels. Because there is less weight on your back two tires they will begin to skid first and any irregularity in the road can cause your car to than travel in reverse. When your car begins to spin in a direction other than the one you are intending your rear tires are beginning to slide, while your front tires are still rolling. The major differences behind these two different motions are the separate forces acting upon your front tires and rear tires. Your front tires have a frictional pull towards the front axle of the car and point partially towards the rear of the car in the direction that the car is spinning. Your rear tires have frictional forces on them directly towards the rear, which is sliding. All these forces create torques which can be defined as a force which rotates an object around its axis. A force is normally a push or a pull, a torque can be thought of as a twist, which is what the car itself is doing. The force of the torques from the friction on the front wheels are much stronger than the torques from the rear wheels. The front wheels begin to move into the direction of the spin causeing an even greater spin which can lead to the reversal of the car.
Another very likely cause behind the spin out of your car has to do with the fact that you do not have an anti-lock braking system. An anti-lock braking system is designed to monitor the rotating speeds of your wheels. When this system detects a rapid deceleration, or a hard brak, it will release the pressure applied to your brakes. This system can really help in maintaining traction with the road and allowing one to effectively steer the car as it slows.
To regain control of your vehicle there is something you can do, however, it does come with a risk. One piece of advice that is given suggests that you turn your front wheels towards the direction of travel that you want. This can create the torque that you want on your front wheels to steer the car back into your desired direction. The risk behind this involves an overcorrection, causing a loss of control in the opposite direction of your initial spin. My best advice would be too find a large empty parking lot, before a spinout on a highway ever occurs, and induce a hard brak and practice your steering maneuvers at a slow, safe speed.