A commonly asked question this time of year is, "Can I install just two winter / snow tires on my vehicle?" To keep the most balanced, predictable and controlled handling possible in all winter driving conditions, it's very important to install four dedicated snow tires on a vehicle.
If you were to put snow tires on just the front or rear of your vehicle, the vehicle would have a split personality. The traction capabilities of the tires on a vehicle play the largest single role in determining how that vehicle will react in any given situation. With the large difference in traction capabilities between winter tires and all-season or summer tires, you can understand the loss of control when one end of the car performs very well and the other end just seems to have a mind of its own.
As an example, front-wheel drive cars oversteer when the winter tires' ice and snow traction on their front axle exceeds that of all-season tires on the rear. Oversteer is exactly what it sounds like: your car turns more than you want it to. This occurs when you lose grip on the rear tires in a corner and the side force pulls the back of the car to the outside of the turn. It causes the rear of the car to swing into the next lane of traffic and if not corrected quickly, allow the car to spin out of control.
Understeer occurs when the car isn't turning as much as you would like. Using dedicated snow tires on only the back of a rear-wheel drive vehicle can push the car, or force understeer, through corners as the all-season tires up front are overpowered by the tires on the rear.
Tires play such an important role in a vehicle's handling capabilities, it's always best to drive on tires that are identical in every detail, including brand, model, size and remaining tread depth. Anything else and you're putting yourself and others at risk. To gain a better understanding of how to control your vehicle in winter's toughest conditions, read "Winter Driving Tips."