2007 Dodge Ram 1500 Pickup Owner's Manual - Page 372

372 STARTING AND OPERATING WARNING! Fast spinning tires can be dangerous. Forces generated by excessive wheel speeds may cause tire damage or failure. A tire could explode and injure someone. Do not spin your vehicle's wheels faster than 30 mph (48 km/h) for more than 30 seconds continuously when you are stuck, and don't let anyone near a spinning wheel, no matter what the speed. Tread Wear Indicators Tread wear indicators are in the original equipment tires to help you in determining when your tires should be replaced. These indicators are molded into the bottom of the tread grooves. They will appear as bands when the tread depth becomes 1/16 inch (2 mm). When the tread is worn to the tread wear indicators, the tire should be replaced. Many states have laws requiring tire replacement at this point.