Snow tires, all-wheel drive, four-wheel drive, bags of kitty litter in the trunk — people will do just about anything to gain an edge when driving in snowy, icy winter weather. For the most part, these strategies are good ideas. After all, winter-slick roads raise the risk of having an accident, and the best way to survive a car accident is to prevent one from happening in the first place. One winter driving trick that some people swear by is underinflating their tires.
To understand why some people think underinflating tires in winter is a good idea, you need to know what's happening when your car goes into a skid (besides everyone in the car freaking out). No matter what the time of year, your car needs traction to stay on the road. Traction is the friction between two surfaces — in the case of a car, it's the friction between the car's tires and the road. That friction allows the tires to grip the road surface and not slide all over the place. The more traction you have, the better control you have. One of the key factors in traction is the tire's contact patch, or the amount of tire that's physically touching the road. The bigger the contact patch, the more traction.
That's what underinflation aficionados are thinking about when they let some of the air out of their tires in winter. When you underinflate a tire, it droops, letting more of the tire touch the road. In certain cases — like driving in some snowy conditions and on sand — underinflating your tires is a great tactic.
There is, however, a rub when it comes to underinflating winter tires, and it goes back to that enlarged contact patch. Extra traction is a good thing when you're driving in the snow, but it becomes a not-so-good thing once the roads are plowed. Underinflated tires will give you (believe-it-or-not) too much traction, which will lead to difficult steering — and a car you can't steer well, obviously, isn't all that safe. Also, depending on the depth of the snow you're driving in, properly inflated tires can sometimes more easily dig through the snow to the pavement below, whereas the wider underinflated tires will ride only on the surface of the snow. Finally, underinflation damages your tires and wheels.
So, underinflating your tires is one winter driving tip that you can definitely skip. Now, keeping a few dozen pounds of kitty litter in your trunk is another story. Not only is it handy when your car gets stuck in the snow, but you'll also have a ready-made litter box for all the neighborhood felines when spring finally arrives.
- Connecticut Department of Transportation. "How to Deal with Ice and Snow!" State of Connecticut. (April 24, 2015) http://www.ct.gov/dot/cwp/view.asp?a=1390&q=259420
- Magliozzi, Tom and Ray. "Car Talk: What's the proper tire pressure on snow, ice? Loser cooks." Seattle Post-Intelligencer. May 4, 2006. (April 24, 2015) http://www.seattlepi.com/news/article/Car-Talk-What-s-the-proper-tire-pressure-on-1202619.php
- Rubber Manufacturers Association. "Winter Driving Tips." (April 24, 2015) http://www.rma.org/tire-safety/seasonal-driving-tips/winter-driving-tips/