Make Sure Your Tires Have Enough Tread for a Snowy Winter
CR testing shows that tires can lose their winter grip at half-tread depth
In wet and wintry weather, all-season tires begin losing traction long before they appear worn-out, according to Consumer Reports’ testing. Tread depth is essential to disperse rainwater and slush, and claw at snow. As tires wear, this ability to hold the road confidently fades.
In CR’s tire tests, we started to see a decline in the performance of tires with half their tread depth still left—well before most drivers would consider replacement.
How We Tested
To assess the impact of tread depth on winter traction, we compared the performance of three popular all-season tires—one set with a full tread and one with only half the tread left.
We shaved tires to about a half-tread depth to simulate a used tire with a lot of life left in it. We tested by accelerating on snow and braking on wet surfaces to assess traction.
We also tracked the speeds at which the tires started to skim or hydroplane on standing water on a road at our Auto Test Center. And we went to a local ice rink to measure stopping distance on ice.
The results show a decline in performance that consumers may experience before the tires are worn-out.
What We Found
A tire with a half-tread depth usually has 5/32 to 6/32 of an inch remaining. Tires are worn-out when they reach 2/32 of an inch, but you don’t need to go that low to see a substantial decline in performance on slick (wet, snowy, or icy) surfaces.
On average with the half-tread tires, there was:
- A 14 percent decline in snow traction (based on the measured distance that it takes a vehicle to get up to speed).
- An 8 percent loss in hydroplaning resistance (based on the observed speed at which hydroplaning first occurred driving through standing water at our test track in Connecticut).
- A 7 percent loss in wet braking (based on the stopping distance from 60 mph on a wet surface, measured at our test track).
- A small loss in braking ability on ice (based on the stopping distance from 10 mph on the surface of a Connecticut ice rink).
When to Replace Tires
To monitor your tire’s tread depth, buy a tread-depth gauge from an auto parts store, or simply use a quarter to judge whether the tires need replacing. If the top of George Washington’s head is just visible when placed head first in a tread groove, the tread has about 4/32 of an inch depth. That’s enough to offer some all-weather grip, but you’ll want to start shopping for replacements. Certainly when any tire groove is at 2/32 of an inch, it’s worn-out and needs immediate replacement. You can check by using a penny; the distance between the top of Abraham Lincoln’s head is 2/32 of an inch.