Enlarge / A closeup of Bridgestone’s latest Blizzak tire in its natural environment. (credit: Bridgestone)
Monday marks the official start of winter here in the US. Not that the weather needs the calendar’s permission; many parts of the country started seeing snow weeks ago. And, of course, you don’t need to wait for December 21 to swap over to winter tires. For one thing, the sticky compounds used in summer performance tires aren’t designed to work when the mercury drops below 45 degrees Fahrenheit (7.2°C), and that can happen well before the ground disappears beneath a layer of snow.
“That has to do with the glass transition temperature of the compounds. The compounds get harder as the ambient temperatures get cooler, and winter tires are designed for a much lower range and temperature,” explained Dale Harrigle, chief engineer at Bridgestone.
That’s partly down to the mixture that makes up a winter tire. “We’re using silica tread compounds in our dedicated winter products. We can tune the dedicated winter products to have good grip at lower temperatures without significantly affecting the rolling resistance we would have 20 years ago. So I believe a lot of the compound and material technology is what’s enabled some of those leaps in performance,” Harrigle told me.