Roger Diez
If you had occasion to try and drive over the hill to California last weekend, you were forcibly reminded that winter driving is a seasonal hazard here. Now, very few American drivers have had the opportunity to drive a racecar, but when you’re driving on snow and ice you get a similar feeling of being on the edge of control. The difference is that the edge is 30 or 40 mph rather than 180 or 200. So, keeping in mind that very few of us have the car control ability of a Kyle Larson, Lewis Hamilton, or Josef Newgarden, here are my annual winter driving tips.
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First, let’s consider the basic physics involved in driving. Say you’re at the wheel of a 4,000-pound vehicle going 30 mph. That’s a serious amount of mass and inertia. This collection of steel, aluminum, glass, and plastic is tenuously connected to the road by four small tire contact patches, and you make any change in speed or direction through those patches. Anything that detracts from the tires’ adhesion to the road (snow or ice, for instance) tends to limit their response to your control inputs. Tires can transmit only three things from the vehicle to the road: acceleration, deceleration, and change of direction. There is a limit, determined by road surface, temperature, tire construction, speed, and other factors, of just how much of these inputs the tires can transmit before they lose grip. Also, when the tire receives multiple inputs, such as braking and steering simultaneously, it creates a vector of the two forces but reduces the absolute limit of either force.
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So now let’s step away from the chalkboard, put our notes down, and put theory into practice. Say your vehicle can stop from 30 mph in 100 feet on dry asphalt. On snow or ice, that distance is going to be doubled, tripled, quadrupled, or might even approach infinity. Remember to slow down in slick conditions, and to increase your distance to the car in front of you. Otherwise, unintended Talladega-style bump drafting might occur with predictable results. Also remember the reference to vectors in our physics lesson. If you try to brake and turn at the same time on a slick surface, both your braking and turning performance will suffer. You will immediately experience what the race driver calls “push,” and you will plow straight ahead with your wheels cranked to the right or left. Similarly, if you accelerate too hard while turning, you will be confronted with the condition racers call “loose.” This will become evident when the rear of your car passes you and you find yourself facing back where you just came from. If you do find the car beginning to pirouette under you, gently turn the wheel in the opposite direction of the spin and slowly ease off the accelerator. Braking at this juncture will lock your wheels and you will lose all directional control.
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To avoid adverse situations in snow and ice, you need to use gentle inputs on all the controls. Brake early and progressively; turn slowly and smoothly, not jerking the steering wheel; and accelerate smoothly, pretending there is an egg under the gas pedal. Situational awareness, something you should always practice when you drive, becomes even more critical in slick conditions. Unfortunately, the level of concentration most people bring to their daily driving is just above comatose. In slippery conditions, this can lead to a trip to the body shop — or worse yet, to the hospital. So be careful, watchful, and stay safe out there.