The ins and outs of tire inflation

Friday, April 28, 2006

Dear Tom and Ray: I am having a dispute with two of my three sons, and I would appreciate seeing what your solution is. Specifically, they claim that in order to increase traction on snow and ice, and even sand, one should remove air from the tires to increase the amount of rubber that touches the road surface. I, on the other hand, contend that this is a dangerous practice and that one should keep tires inflated to the manufacturer's recommendation, or perhaps even increase the pressure under the above conditions. Please tell me I'm correct. Doing all the cooking at deer camp hangs in the balance.


Ray: Put on your apron, Tommy boy.

Tom: Your sons are, technically, correct -- although as a practical matter, you can make a good case for leaving the tire inflation alone.

Ray: Here's the story. On a slippery surface, like ice, compacted snow or sand, the larger the contact patch on the ground, the more traction you'll get. And "flattening" the tire does give you a larger contact patch.

But here's the practical part of the problem: As soon as you get off the compacted snow, it IS dangerous to drive around with underinflated tires. So, unless you carry your own battery-powered air pump, this is not a practical thing for the average driver to do.

Tom: Let's say you're at deer camp. Overnight, it snows 6 inches and you have to drive out. You lower your tire pressure 10 or 15 pounds to give you more traction when you drive on top of this snow.

Ray: But you get out to the highway, and there's no gas station, or no air available. And the highway has already been plowed. Then you're in a position where you're going to be driving at highway speeds with seriously underinflated tires. That not only compromises your handling, but increases the chances of an accident or rollover, because underinflated tires tend to overheat, and overheated tires explode.

Tom: There are two other points we should make. In snow, there ARE times when you don't want a wide rubber patch. Here's where you might be able to get the kids to at least peel some potatoes, Tom. If the snow is just a couple of inches deep, you'll usually do better with a normally inflated, narrower tire, which can bite through the snow down to the pavement, where the tire can get some real traction. That's why snow tires are often narrower than all-season or summer tires.

Ray: But there are no circumstances when overinflating the tires will help you get more traction. Overinflating leads to a narrower tread patch, less friction and less traction -- which is why it's associated with slightly higher fuel economy.

Tom: So, you guys are going to have to fight it out regarding who cooks at deer camp, Tom. But for your average Tom, Dick and Harry (your sons aren't named Dick and Harry, by any chance, are they, Tom?), it's best to stick to the manufacturer's recommendation for tire inflation, enjoy longs WALKS on the beach, and stay home and watch "Columbo" reruns when it snows.

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