Tread depth is an important tool to measure whether a tire is safe to drive on, but that doesn't explain the unusual ...

To test, first make sure your car is parked on a level road. Turn one of your tires ... a penny: Insert it head down and see ...

The bars become flush with surrounding tread when wear reduces a groove's depth ... tire. Our half-tread tires began to skim over the water's surface at as slow as 40 mph in our hydroplane test ...