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Why Do Tires Need Air? The Story of Air-Filled Tires, from Bicycles to Giant Wheels

Category: Technology

Bicycle tires are thin, while car tires are thick. Which one has the air packed in tighter? The answer might surprise you. It is not just about size; it is about how the air supports the vehicle. But first, we must ask: why do we put air in tires at all?

This question leads us back to a Victorian-era problem, a forgotten patent, and some very large wheels. Let’s look at how air changed the way we travel.

1. How a Vet, John Boyd Dunlop, Made an Air-Filled Tire for His Son

John Boyd Dunlop was a veterinarian, but his invention helped change how people traveled. His son, Johnny, suffered headaches every time he rode his tricycle. The roads were full of stones and bumps, and the tires at the time were made of wood or hard rubber. These materials did not absorb the shock, so each bump jolted Johnny. [1]

In 1888, Dunlop wanted to solve this problem. He came up with a new idea: he took a rubber tube, filled it with air, and wrapped it around the wheel. This gave shape to the idea of an air-filled tire. After Johnny switched to these new air-filled tires, his tricycle ride became much smoother and more comfortable. [1]

2. Robert William Thomson Patented the Air Tire 40 Years Earlier

Dunlop’s invention became very popular, but there was a twist in the story. It turned out that another inventor named Robert William Thomson had already patented a similar air-filled tire idea. Thomson had filed his patent 40 years before Dunlop, in the 1840s. [2]

Because Thomson’s patent existed, Dunlop’s patent was later declared invalid. Despite this legal setback, Dunlop is still remembered today as the person who popularized the air-filled tire. [2]

3. How Air Inside a Tire Works Like a Spring

Whether it is a bicycle or a car, the system inside the tire is the same. Think about pressing a balloon. It dents in slightly and then bounces back to its original shape. The air inside a tire works in a similar way. When the tire hits a bump on the road, the air compresses to absorb the shock. [3]

This cushioning effect is crucial. If tires had no air, they would be like solid wooden wheels. Every small stone or crack in the road would send a jolt directly to the vehicle and its passengers. The air acts as a spring, smoothing out the ride. [3]

4. Why Bicycle Tires Have Higher Air Pressure Than Car Tires

Here is a quiz: Which tire has the air packed in tighter, a thin bicycle tire or a thick car tire? The answer is the bicycle tire. Bicycle tires require much higher air pressure than car tires. [4]

The reason lies in the contact area with the ground. A bicycle tire touches the road over a very small area. To support the rider’s weight without the tire collapsing, the air inside must be under much higher pressure. Car tires touch the road over a larger area, so they can support the heavy vehicle with lower pressure. [4]

5. Bridgestone Built One of the World's Largest Tires in Japan

Bridgestone, a Japanese company, once created one of the largest tires in the world. At the time it was made, it was the biggest tire in existence. Its diameter is over 4 meters (about 13 feet), which is taller than a giraffe. [5]

The tire weighs more than 5 tons, which is close to the weight of a single elephant. These massive tires are used on giant dump trucks that work in mines. They are designed to carry enormous loads, showing how tire technology scales up for heavy industrial use. [5]

6. Why Low Tire Air Pressure Is Dangerous

Tire air leaks out slowly, even if you do nothing. It decreases little by little every month. [6]

The Japan Automobile Federation (JAF) conducted an experiment to show the risks of under-inflated tires. They tested tires with low air pressure at high speeds. The surface of the tire began to wave like a ripple, and the temperature rose above 100 degrees Celsius (212 degrees Fahrenheit). Eventually, the tire burst. [6]

In contrast, tires with the correct air pressure kept their temperature around 60 degrees Celsius (140 degrees Fahrenheit) at the same speed, and no problems occurred. In the experiment, tires with insufficient air pressure burst. [6]

7. How to Check Your Own Bicycle Tire with an Adult

If you want to learn more, look at your own bicycle tire with an adult. Press it with your finger to see if it feels hard or soft. You might find small numbers written on the side of the tire. These numbers often tell you the correct amount of air pressure for that specific tire. [6]

SAFETY NOTE: Always use an air pump or pressure gauge with an adult. Do not over-inflate the tire, as this can be dangerous. [6]

Sources

  1. Wikipedia (English edition) "John Boyd Dunlop" https://en.wikipedia.org/wiki/John_Boyd_Dunlop (Dunlop invented the pneumatic tire in 1888 for his son's tricycle, replacing wood and hard rubber tires.)
  2. Britannica "Pneumatic tire" and other encyclopedic entries https://www.britannica.com/technology/pneumatic-tire (Robert William Thomson patented the pneumatic tire in the 1840s, but it was forgotten until Dunlop's patent was invalidated around 1890.)
  3. General explanations of tire structure and function (automotive engineering basics) (The air inside the tire acts as a cushion to absorb road irregularities and distributes the vehicle's weight over the contact patch.)
  4. Multiple expert articles on bicycle and automobile tire air pressure (Bicycle tires require higher air pressure than car tires because they have a smaller contact area with the ground.)
  5. Bridgestone official site "Bridgestone Story" and Merkmal "The World's Largest Tire" https://www.bridgestone.co.jp/corporate/history/story/10_03.html https://merkmal-biz.jp/post/99316/2 (The 59/80R63 tire has a diameter of 4.02m, weighs 5.1t, supports over 100 tons, and was a Guinness World Record holder in 2001.)
  6. JAF "Tire Bursting Due to Low Air Pressure (JAF User Test)" https://jaf.or.jp/common/safety-drive/car-learning/user-test/driving-environment/burst (In a 2016 test, under-inflated tires at 200km/h caused standing wave phenomena and temperatures over 100°C, leading to bursts, while correct pressure kept temps at ~60°C.)