Inflatable tires were invented in the 1800s and are still everywhere today, even though they have to be pumped regularly and sometimes go flat or explode.
Inflatable tires have many disadvantages. They can be too bloated in the summer, too low in the winter, or suddenly explode on the highway. So why does the world still use inflatable tires today?
The first patent for an inflatable tire was granted in England in 1845, to inventor Robert William Thomson of Middlesex, England. “During every part of the rotation, the wheels create a cushion of air over the ground, rails or other type of road on which they run,” he said, describing his design.
“I have invented or discovered a new and useful improvement in the carriage wheel, which is also applicable to other rolling bodies,” Thomson wrote further. He said adding elastic seals around the wheels reduces the force needed to pull the carts, making them move more easily and reducing the noise emitted when running.
This invention appeared long before the advent of synthetic rubber, the material that accounts for the majority of rubber used in the tire industry today. Therefore, Thomson recommends using sulfur rubber or gutta-percha material and then inflating it.
This is a breakthrough invention: easy to make, low cost and can bring major improvements to everyday life. But it’s strange that it hasn’t evolved further over the decades, and it took another inventor to truly make inflatable tires popular.
John Boyd Dunlop is a Scottish veterinarian who moved to Belfast, Northern Ireland. In 1888, watching his son struggle to ride a tricycle on a gravel road, he was inspired to invent – or re-invent – the pneumatic tire to help the boy get rid of his aches and pains.
Similar to Thomson, his design used rubber treated with sulfur – a method developed by Charles Goodyear in 1844 and known today as vulcanization. But the difference is that Dunlop’s tires succeeded quickly.
First, he actually makes and sells them, which is helpful if you want to be commercially successful. Second, he was also lucky. “The bicycle boom peaked when Irish cycling champion Willie Hume bought a set of Dunlop tires for his bike the following year,” author Suze Clemitson explains in her book A History of Cycling in 100 Objects published in 2017. Hume became the first cyclist to use inflatable tires in competition and it is said that riding on these tires brought victory.
Two clear advantages of inflatable tires compared to previous hard tires are increased speed and comfort. So why was air chosen for pumping?
As a gas, air can compress more than any solid material – which is important when there are only four wheels to bear the weight of a car weighing up to 1,600 kg. Even lighter vehicles like bicycles inevitably deform the wheels a bit – which is a good thing because it increases the amount of the wheel touching the road, providing more traction for the vehicle – and with air-filled tires, this requires Requires much less energy than solid tires. This is why the first users of Dunlop tires rode their bikes so much faster than their competitors. Inflatable tires make it easier to move at higher speeds and consume less energy.
In physics, this is called “rolling resistance”: the energy consumed by the tire per unit distance traveled. Simply put, low rolling resistance is better, and inflatable tires have an advantage over solid tires. The reason is not only its malleability, but also the fact that air is lighter than solid rubber. Given the same deformation, the heavier the object, the more heat it releases, and that heat loss results in higher rolling resistance.
All of the above advantages become even more obvious when the driver drives on the road at a speed of nearly 100 km/h and suddenly encounters a pothole. At that speed, a sharp obstacle that suddenly appears will cause an extremely strong shock to the solid wheel – the type of wheel that can only absorb local shock. Meanwhile, the air will dissipate the impact on the entire wheel, making driving smoother.