Our car guy has advice on how to keep on the road in the cold
Winter weather is more than just snow, although I don’t think anyone would be surprised by anything this year. As far as your car is concerned, temperatures below 40° are winter, and by Monday, Nov. 7th, the average low is 43, dropping to 40 by the 15th. That’s just over two weeks away. But what actually happens? It’s a combination of things involving your tires and the road.
First, rubber. Somewhere over 50 percent of the carcass (the “rubber” part of a tire) is actual rubber, made from tree sap. Rubber’s great trick is that when heated properly (vulcanised) it takes whatever shape you’ve given it--and never changes again. You can’t melt it back down, because it’s changed chemically and isn’t the same rubber any more.
That’s been a huge problem for recycling, but it’s also a problem in making them, because it can only be one thing. This is why there are summer, winter and all-season tires—because their materials have to be different.
Most people settle for all-season tires, which aren’t as good in warmth as summer tires or as good in the cold as snow tires. I could probably draw a line somewhere across the country where it makes sense to have snow tires (I’ll call this imaginary line the “Mason-Dixon” line), but that doesn’t mean what you have on your car is the right thing.
The difference is how these things interact. For summer, you want something that holds up to heat, and stays stiff enough to handle cornering and braking on a road surface that could easily be 140 degrees. It also needs big channels to get rid of water and prevent hydroplaning, which is when water gets between your tire and the road, making you float away.
In winter, you need a tire that stays flexible in the cold and remember, “cold” means 40-ish, which turns out to be the limit of our current tire technology. We can’t make a rubber compound that excels across that barrier: It’s one side or another; or a little bit of both, which is what an all-season tire is, a compromise.
Ninety-five percent of you, then, are rolling on less-than-ideal tires, particularly troublesome at the end of summer. Your mediocre all-season tires have endured more than three months with temperatures above 90 degrees, accelerating wear, as well as breaking them down chemically. But last weekend it was into the low 40s, and the stiffening of your tires combined with changes in the road surface to make driving very different, whether you realized it or not.
All-season tires perform particularly badly in wet conditions—in an Edmunds test they came in last, worse than both snow and summer tires, in braking (by 58 feet!), handling and acceleration. Their conclusion? “Anyone who never sees or visits snow would be very well served by summer tires for year-round use.”
You can use this information to change your driving habits not just in the event of snow, but based on the temperature or even time of day. Imagine everything getting slicker as it closes in on 40, and the effect of rain being magnified. Situations that are fine at lunchtime might become hairy after dinner, as you pass the critical threshold of slipperiness.
On a bright, crisp day, the threshold might be between light and shadow. You’re heading into a curve and go under some trees, where it’s 10 degrees colder and slightly damper, and what was adequate traction, isn’t, any longer.
It’s like looking ahead for any other kind of hazard or potentially dangerous situation. Is it getting dark? Slow down on the curves. Is it raining and cooling off? Watch out for standing water on the road. Do you not know the last time you got new tires or at least had them rotated? Maybe stay off the highways altogether if it’s any of the above.
It’s not just stuff on the roads that changes in the fall. The road itself is different, and so is your car. You need to drive differently to be safe.
David Traver Adolphus is a freelance automotive researcher who recently quit his full time job writing about old cars to pursue his lifelong dream of writing about old AND new cars. Follow him on Twitter as @proscriptus.