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One of the most common Canadian debates guaranteed to come up in the fall is whether studded winter tires are better than un-studded tires. This issue is further clouded by tire manufacture ads claiming that their studless winter tires outperform studded tires in both performance and stopping distance.

Those who have studs usually swear by them. Those who don’t, have their own rationale for why they are unnecessary. It’s fine to have your opinion but we wondered if there was any way to back that opinion with facts. We went looking and found some interesting information to shed some light on the stud vs. studless issue. We found exactly what we were looking for in a 2008 Russian study.

So the definitive answer to the question, are studded tire better than studless winter tires is (drum roll please), it DEPENDS (sigh of disappointment). Let us explain!

The study showed that studless tires did indeed outperform studded tires at low temperatures and under certain circumstances. The equilibrium temperature which they performed equally was -13°C. Below that temperature the studless tires did perform better giving a basis to the manufacturers' claims. Simply put, at temperatures below -15°C, the ice gets harder and the studs will chip the ice rather than penetrate it and the advantage of the stud disappears. However at ice temperatures above -15°C, the stud can imbed itself into the ice allowing dramatically more traction and control offering a safer and more comfortable drive.

Interestingly, the study referred to studless winter tires as Velcro tires. While it may not be an accurate description of the materials, it paints a pretty good picture of their operation. Like any Velcro surface, it’s stickiness can be affected by a number of factors. Its best performance is on a cold, uneven ice surface. Winter tires are made with softer rubber and incorporate sipes (squiggly lines cut into the rubber) into their tread design. These sipes work in conjunction with the rubber pliability to give an overall performance in the tires gripping power. As ice becomes smoother, coated in frost and/or begins to melt, winter tires components become less effective. This is where studded tires shine, gripping into ice like golf shoes into the middle of a fairway.

Let’s get an idea of how this plays out in the real world. Using data from the Russian study with a standard mid sized car travelling at 50 km/h on a level, bare ice surface with the brakes evenly applied to come to a full stop. At -20° C, a winter tire would take 32m to come to a complete stop to a studded tire’s 38m. At -15°C they are nearly the same at 35m but performance shifts significantly above that temperature. At -10°C studded outperforms studless by a full 12m, 32m to 44m respectively. At -5°, when the studded tire performs optimally, you’ll see a stopping distance of 29m whereas the studless loses performance and takes nearly double the distance to stop at 54m. That is six car lengths difference!
 

So, back to the question.

The, “depends” part of the question really has to do with the conditions you are most likely to encounter, mostly driven by temperature. The mean temperature in Calgary in December through February is -6°C. That’s pretty much the temperature that studded tires are their optimum effectiveness. Winter tires on the other hand dramatically fall off in performance above -13°C. The answer to the question would be completely different if you are in say Ft. McMurray where the average temperature for the same time period is -16°C and are more prone to periods of temperatures much colder than that. In this area, studded tires don’t make as much sense. For the Calgary environment however, studded tires are the clear winner. With our milder winter temperatures combined with our frequent chinooks, black ice and wet ice are quite frequent on Calgary roads. This is the environment where studded tires perform at their best.

One other factor to consider in your decision is that studded tires stopping distance is much more consistent, regardless of temperature (see graph above). Studless tires can give you an unexpected surprise at temperatures above -10°C to 0°C. This is especially true for more inexperienced drivers.

Hopefully, this article will help to shed some light on a subject that marketers like to "muddle" with in order to bend opinion to their favor. If you have any questions or would like to discuss further, feel free to connect with us.

Safe driving.

*temp chart courtesy of weatherspark.com