How do 30 pounds of air in your tires hold up 2 tons of car?
How do 30 pounds of air in your tires hold up 2 tons of car? The next time you get in your car, take a close look at the tires. You will notice that they are not really round. They are squished at the bottom. The flat spot on the bottom where the tire meets the road is called the contact patch. If you were looking up at a car through a glass road, you could measure the size of the contact patch. You would multiply the length of the contact patch by its width to get the area, then add up area for all four tires to get the total area of the contact patch. For your 2-ton (4,000 lb) car, you will find that the area of the contact patch is about equal to the weight of the car divided by the tire pressure. In this case 4,000 pounds divided by 30 pounds per square inch equals 133 square inches. That may seem like a lot, but your car’s tires are probably about 7 inches wide. That means that the contact patch for each tire will be about 4.75
