Tire Tech

Choosing tires is a tricky business. Not only is there a slew of brands and models out there, but tires are further divided along performance and weather lines. So which will work best for you?

We're here to help. In this installment of our ongoing tire tests, we investigated the performance differences among three types of tires -- snow tires, high-performance tires that promise the best traction in warm-weather conditions, and all-season tires. Furthermore, we selected all three tires from Goodyear's Eagle family because every Eagle tire has a higher-than-average performance quotient. The recently introduced Eagle Ultra Grip GW3, for example, is a snow tire specifically made for drivers of performance cars.

All snow and ice tires employ tall tread blocks, a more open tread pattern, narrower tread, and soft rubber compounds to enhance grip in the slippery stuff. Unfortunately, those features tend to produce freeway hum and an unsatisfying, squirmy feel on dry roads. And even those of us in snowy climates spend most of our winter months driving on plowed pavement. This new Eagle Ultra Grip is designed to get you through the snow, while maintaining more dry-road performance than typical snow tires. The tire also comes in higher speed ratings (H and V) than most snow tires. They cost $160 each.

Our all-season contender was the Eagle RS-A ($137), and the high-performance summer tire was the Eagle F1 GS-D3 ($155).

Since we were testing only Goodyear tires, there was no unfair advantage to using Goodyear's facilities. We ran the snow tests at Goodyear's Ironwood, Michigan, winter-testing facility, and for wet and dry running we relied on the company's Akron, Ohio, test track. We also used Goodyear's Cadillac CTS for all the tests, and that dictated the tire size used -- 225/55R-16 for all three tires.

Testing in snow poses unique challenges in consistency, so we performed tests at Ironwood different from those we conducted in the dry at Akron. Bear with us, and the differences will become clear.

IN THE SNOW

Ironwood is high up in Michigan's Upper Peninsula, just 10 miles from the shore of frigid Lake Superior. It's a land of bitter cold, but on the sunny day we were there last March, the temperature ranged from a balmy 20-to-24 degrees Fahrenheit. The facility is basically a six-lane, 2200-foot straightaway.

Testing on snow is no picnic because the available traction is based on many variables. Snow at 30 degrees is more slippery than 15-degree snow because there's more moisture in snow when it's warmer. If you drive over the same area repeatedly, you create ruts in the snow that also affect traction. Since measuring lateral acceleration by repeatedly driving the car in a circle (our usual skidpad procedure) or running a handling test would create deep ruts that would change the traction from one tire to the next, we didn't attempt to run a snowy skidpad.

Therefore, on the snow we only measured the acceleration and braking performance of the tires. Given our available space, we measured the 0-to-50-mph acceleration time and the distance required to stop from that speed with each tire.

Not surprisingly, the snow tire was the best performer. With it we were able to accelerate to 50 mph in 14.2 seconds and stop in 245 feet. As we expected, the all-season RS-A lagged behind, being 3.4 seconds slower in acceleration and needing an extra 20 feet to stop. Those differences might not seem large enough to justify snow tires. And for sure, if your car has all-season tires on it and you live where it doesn’t snow often, you can probably get away with them. But as you'll see, any car with high-performance summer tires is going to need another set of tires for the winter months.

The high-performance Eagle F1 got an F on the snow. We only managed to reach 11 mph, and that was with two burly guys pushing. Otherwise, it was wheelspin city. Let us be clear here: Don't attempt to drive on snow with high-performance summer tires. Even if your car has four-wheel drive and can manage to get moving, four-wheel drive can't help the car turn or stop. That’s the tires' job.

WET AND DRY DRIVING

Goodyear's Akron test facility has a huge 400-by-1000-foot asphalt pad, room enough for a 60-mph-to-0 braking test, a 200-foot-diameter skidpad to measure lateral grip, and a 0.56-mile coned autocross course. Since our loaner Cadillac CTS had a 220-hp engine that doesn't easily spin the tires during hard acceleration on dry pavement, there would be a negligible difference among the tires during a quarter-mile run. So we didn't do acceleration tests at Akron. Sprinklers were used to water down the area, so the three tests we ran were performed in wet and dry conditions.

The dunce of the snow test -- the Eagle F1 -- was the ace at Akron. It posted the fastest times through the autocross course in the dry and wet -- 51.02 and 53.37 seconds, respectively -- and pulled the most lateral g -- 0.84 g dry and 0.75 wet. Also, the tire performed terrifically under braking, requiring the same 132 feet to come to a standstill on both wet and dry surfaces.

The most interesting result was that the snow tire performed better on wet asphalt than did the all-season tire. The snow tire stopped sooner -- 150 feet versus 155 -- and pulled more g -- 0.71 versus 0.69. And its 56.60-second run through the wet autocross course was 0.11 second quicker. But on the dry surface, the results were reversed, with the all-season tire outperforming the snow tire. Most notably, the all-season tire's time through the dry autocross (52.15 seconds) was more than a second better than that of the snow tires.

Still, though, the snow tire was fairly impressive. Until now, we had never tested a snow tire on hot, dry pavement, and we didn't expect its performance to be remotely close to the others'. The Ultra Grip had much less of that loose, imprecise feel that we've experienced with other snow tires, and we wouldn't hesitate to attack an off-ramp with it. Be warned, however, that the Ultra Grip shouldn't be used year-round. Its rubber compound was designed to work in the cold, and after our testing on the hot, dry track (it was 77 degrees and sunny that day), the Ultra Grip looked noticeably more worn than the two other tires.

Obviously, for the best all-around performance, you should use a tire like the Eagle F1 during the nonwinter months and switch to a snow tire like the Ultra Grip GW3 when the white stuff is coming down. Of course, this requires an investment in a second set of tires, finding a place to store the off-car set, and a willingness to swap tires twice a year (it's easier when the snows are mounted on their own wheels). It also means that during those winter months when the pavement is not covered by the cold white powder, you’ll experience a noisier and less responsive ride.

That's where the all-season tires have their place. They work reasonably well year-round without ever leaving you in the lurch. But whatever you do, if you live in a cold northern climate, don't even think about driving through the winter on those wonderfully grippy summer tires.