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An important PSA about driving safely in bad weather
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Nowhere does consumer perception lag further behind on-the-ground reality than in the car world. And that’s a problem, because your outdated beliefs, loyalties, and superstitions are probably costing you money and compromising your safety.
We discussed just that last year, when I told you that running winter tires matters way more than buying an all-wheel drive car. But that article had one major flaw: I neglected to explain why studded tires are so vastly inferior to the modern studless alternative. And readers have since indicated that they are actually running studded tires in conditions that don’t merit them. This is my attempt to fix that.
If you don’t read any further, the fact that studs only provide additional grip on clear ice is probably the most important takeaway I can give you. Studs themselves are small, sharp metal protrusions installed into the tread of a tire. Because they get between the rubber and whatever surface you’re driving across, they need to be able to poke into that surface and momentarily stick there, resisting lateral forces, in order to provide grip.
Picture other winter surfaces: in packed, loose, or deep snow, the studs will definitely penetrate, but they won’t find the resistance necessary to actually add grip. In slushy or wet conditions or on bare pavement, the tire needs to come into contact with the road surface in order to find traction—and the metal studs actually get in the way of that.
So studs help on bare ice only, do nothing for you in snow, and actually make you less safe in other conditions.
For last year's article on all-wheel-drive versus better tires, I interviewed Woody Rogers, the head of Tire Rack’s testing team. Because Tire Rack is the largest online tire retailer, Rogers tests virtually all makes and models of tires and his job is to be as objective as possible. Tire Rack doesn’t care about selling you a specific tire; they care about selling you the best tire for your needs. “Drivers can’t dictate the surfaces they drive on,” he told me. “They just need a tire that works across all the hazardous conditions they face in winter months.” And that’s not studs.
Back in 2001, Washington State conducted an exhaustive study into the performance of studded tires. One of its most interesting conclusions was that, while studs do grip clear ice very well, they only do so under a very specific set of circumstances.”Studs are most effective on ice at or near 32 degrees F and lose their efficacy as temperatures drop and the ice becomes too hard for the studs to grip or when temperatures rise and ice melts to slush or wet pavement,” the study reads. The minimum effective temperature for studs? Zero degrees Fahrenheit, according to the study.
And that’s a huge problem, because bare ice in those temperature ranges where studs help only exists on roadways for a very small amount of time. In Washington, the study found that conditions where studs work only exist one percent of the time. In Alaska, those conditions occurred just six percent of the time during winter months. In Connecticut, that number is just half a percent. In Ontario, bare ice between zero and 32 degrees accounts for less than two percent of vehicle miles traveled.
Go back to Rogers’s quote above, and you’ll see why having a tire that only works as advertised in such specific, rare circumstances will be problematic. I called him back up for help with this article. “There is absolutely a time and place where a studded tire is a superior solution,” he tells me. “But I don’t know a place in the U.S. where conditions merit studs all winter. So, you have to consider managing the tradeoffs.”
Tiny metal spikes don’t grip pavement as well as soft, pliable rubber. So, by getting between the rubber and the road, studs actually reduce grip, and therefor safety, in slushy, wet, or dry conditions.
A study conducted in Alaska in 1994, soon after the advent of modern studless winter tires, compared the braking, acceleration, and cornering performance of studded, studless winter, and all-season tires across packed snow, clear ice, and bare pavement. Studded tires demonstrated some advantage in braking and acceleration on bare ice, were actually out-cornered by studless winter tires, and were demonstrated to reduce grip in all tests on bare pavement. Consider the small fraction of the time in which conditions merit studs and you can see that you are sacrificing grip—and, again, safety—throughout most of the winter.
“There is absolutely a time and place where a studded tire is a superior solution. But I don’t know a place in the U.S. where conditions merit studs all winter. You have to consider the tradeoffs.”
And that's assuming your studs are in good condition. “Think about how much of your driving here in the U.S. is spent on non-snowpack roads,” says Rogers. “And that is wearing at the studs, blunting the sharpness of them, and wearing them down. That takes away some of the traction advantage.”
How much grip is lost as studs wear? “When stud protrusion diminishes to 0.024 in. (0.6 mm), the frictional effect from the studs becomes negligible,” concludes the Washington study. It found that after just 1,000 miles of driving on bare pavement, the braking distance of studded tires increased by 12 percent.
Studs aren’t the only things that wear when they’re driven on bare pavement. The road surface itself is also torn to pieces. By damaging pavement so significantly, studs actually create a significant amount of pollution, throwing microscopic asphalt and concrete particles into the air. In Japan, concerns about this type of pollution led to the development of moderns studless winter tires in the early 1990s. Studs are now banned in that (very snowy) country.
“And then there’s the noise,” says Rogers. “The noise is crazy. I still remember the first time we drove on studded tires as part of a test here, I was in a caravan with other cars, and we had a studded car and a studless car. I was an eighth of a mile behind the studded car, and even with the windows up, I could here the noise from the tires of the car ahead of me.”
All that for a small advantage in one specific circumstance that only accounts for a tiny fraction of the miles you’ll log during the winter?
Back in the 2000s, when it was my job to test new cars, I once crashed a Corvette into a bank of frozen snow way up in northern Sweden. Why? Well, because I’m an idiot, obviously. But part of the reason was also due to the unique handling characteristics of studded tires, which I failed to fully account for.
“With a studded tire, what we’ve found particularly during braking and acceleration, is that once the tire spins, the studs cut a groove in the ice,” says Rogers. “Then the next stud that comes along behind it comes right through that same groove and has nothing to grab onto.” It only takes about a quarter of a revolution for that effect to take place, and once it occurs, grip disappears instantly.
“That leads to what you felt in the Corvette,” Rogers tells me. “Grip, grip, grip, grip, grip, then whoops—who pulled the rug out?”
Even if you’re not lapping a car around a race track carved onto a frozen lake, this lack of communication from studded tires could impair your ability to drive safely in winter conditions. Whereas studless tires lose their grip progressively, communicating to the driver that they’re nearing the limits of available grip, studded tires lose grip suddenly, without warning. You won’t know you’re driving too fast for the conditions until you end up in a ditch.
The simple answer is that studs are an outdated technology that's no longer relevant in the vast majority of driving conditions.
“The traction of studded tires is slightly superior to studless tires only under an ever-narrowing set of circumstances,” the Washington study concluded—way back in 2001. “With…the advent of the new studless tire, such as the Blizzak, since the early 1990s, the traction benefit for studded tires is primarily evident on clear ice near the freezing mark, a condition whose occurrence is limited. For the majority of test results reviewed for snow, and for ice at lower temperatures, studded tires performed as well as or worse than the Blizzak tire. For those conditions in which studded tires provided better traction than studless tires, the increment usually was small.”
This winter, will you drive in extreme cold? Will you drive on snow? Will you encounter bare, plowed highways? Winter driving is defined by its unpredictability. Fortunately for all of us, there is a device designed to deal with all of it: The modern studless winter tire.
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