Tires naturally wear down as you use them ... For an Australian 20-cent: Put the coin right side up. The tread should cover the platypus' bill. If it doesn't, you should start preparing to ...

Although a typical tire-rotation interval is 5,000 to 10,000 miles, you may want to have the tires rotated before it’s called for if you notice uneven tread wear that results in vibration or noise.

The result is hydroplaning, where the tread skims the water's surface and the vehicle no longer responds to the steering wheel. Wet-weather braking and snow traction also decrease as tires wear.