Tread depth is crucial to your safety! Once the tires on your car get below a certain minimum tread depth, your steering, handling, and traction are compromised seriously enough that your car is considered unsafe to drive. Most states cite 2/32” as minimum tread depth, but the truth is that your traction in wet weather or snow can be treacherous long before the tread makes it to 2/32”.
Most tire brands have “wear bars” embedded in the tread grooves, at a right angle to the tread. Once the wear bars start to show through, it’s definitely time to replace the tires.
The oldest rule-of-thumb test is the “Lincoln head penny” test – insert a penny into the tread, with Lincoln’s head pointed down. If the tread doesn’t come to the top of Lincoln’s head, you are below the 2/32” minimum. The same test can be done with a quarter – the top of Washington’s head equals 4/32”. The backside of a penny can also be used – the top of the Lincoln Memorial equals 6/32”. Take measurement at several points along the circumference of the tire, and run your hand along the tire’s tread surface. Uneven wear along the circumference (or “feathering”) can be an indicator of suspension problems or other mechanical issues.
All that having been said, there are ways to get the most out of the tread life on your tires, long before they get to that point.
- Be mindful of your tire pressure. Radial tires don’t deform much at the bottom until they start to get drastically low on pressure, and a tire that’s ten pounds low may look completely normal. Underinflated tires will wear prematurely, though, as well as affecting your car’s handling and drivability and gas mileage. Check tires for proper inflation at least once a month, with a quality tire gauge (don’t rely on the ones built into the air hose at the gas station).
- Get your tires rotated regularly. Regular tire rotations will extend tire life, stop uneven tire wear and help your car’s ride, handling and drivability. Most dealerships will give free tire rotations for the life of the tire, so figure on a tire rotation every time you get your oil changed (every 3000-5000 miles).
It comes down to this: 2/32” is really a bare minimum, and is not safe for wet weather. Remember that water cannot be compressed and needs enough room to be evacuated from your treads as the car goes down the road. Without that evacuation of water, your tires will actually ‘float’ or hydroplane on the film of water between them and the road. 4/32” should be considered a minimum for wet roads, and 6/32” for snowy conditions.
Pay attention to how your car’s handling and traction feel while driving, and keep in mind how many miles are actually on your tires, to begin with.
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