What is the purpose of inflating our tires with air?

Occasionally, the task of car maintenance can be reminiscent of a full-time occupation. It is essential to ensure that your engine is lubricated, your washer fluid is topped up, and your spark plugs are functioning optimally. There are many more items to add to the list. And supporting all of them are four of the most fastidious individuals you have ever encountered: your tires.

The tires experience excessive inflation during the summer and insufficient inflation during the winter. Additionally, they have the tendency to unexpectedly burst while driving on the highway, potentially causing a forceful impact with the hard shoulder. The issues associated with the tires are incessant. One might question why we bother to have air in our tires.

This question may not appear as foolish as it initially sounds. Indeed, certain vehicles, such as tanks or industrial vehicles like forklift trucks, operate efficiently without the need for air-filled tires. However, when it comes to our automobiles, trucks, buses, and even aircraft, we adhere to the reliable and sufficiently effective combination of rubber and a precise quantity of air.

Indeed, there is a highly valid explanation for that.

The initial pneumatic tires
Given the extensive duration of the existence of the wheel, the notion of adorning it with bulky outer garments—incidentally, this is the origin of the term “tire,” which is a contraction of the wheel’s “attire”—is unexpectedly recent.

Robert William Thomson, a resident of Middlesex, England, filed the initial patent for a pneumatic tire, which is a tire filled with air, in the United Kingdom in 1845. His patented design, introduced in the United States in 1847, ensured that the wheels would consistently create an air cushion between themselves and the surface they traveled on, be it the ground, rail, or track.

“I have created or found a new and beneficial enhancement for carriage wheels, which can also be used for other objects that roll,” he proudly declared. According to his statement, if elastic bearings were applied around the tires of the wheels, which are the solid steel or rubber rims attached to the outside of the wheels, it would result in a reduction of the power needed to pull the carriages. This would make their movement smoother and decrease the noise they produce while in motion.

Prior to the development of synthetic rubber, which now dominates the tire industry, Thomson suggested utilizing “sulphurized caoutchouc or gutta-percha and inflating it with air” for his design. However, the concept is essentially this: acquire a material made of rubber or a similar substance, inflate it with air, and allow your buttocks to express gratitude afterwards.

As far as inventions are concerned, it was essentially the ultimate achievement: a simple and inexpensive modification that would bring significant enhancements to people’s daily lives. It is perplexing that no progress was made for many years, and it required a completely different inventor to initiate advancements in the tire industry.

The pursuit of comfort
While the inspiration behind Thomson’s work remains unknown, John Boyd Dunlop, a prominent figure in the history of pneumatic tires, had a clear motive for his invention. He filled rubber tubes with air and attached them to wheels for the sole purpose of benefiting his child.

In her 2017 book “A History of Cycling in 100 Objects,” cycling journalist and author Suze Clemitson stated that John Boyd Dunlop, a Scottish veterinarian, had moved from Scotland to Belfast. Observing his son struggling with the bumpy surface on his tricycle, he was motivated to create—or recreate—the pneumatic tire with the intention, as reports suggest, of alleviating his son’s frequent headaches or discomfort in the buttocks.

Similar to Thomson, Dunlop’s design included sulfur-treated rubber, a process known as vulcanization that Charles Goodyear invented in 1844.Like Thomson, Dunlop’s tires gained immediate popularity. What is the reason? There are two primary reasons for this: Firstly, he actively manufactured and marketed them, which undoubtedly contributes to achieving commercial success. However, he was also fortunate: “The popularity of bicycles was at its peak when Irish cycling champion Willie Hume bought a pair of Dunlop tires for his bike the next year,” Clemitson clarified. Hume was the pioneer who introduced pneumatic tires in competitions and reportedly never lost a race while using them.

Setting aside any internal disputes among Scottish inventors, there are already two clear benefits of using air-inflated tires compared to solid ones: increased speed and enhanced comfort. However, what is the reason for that to be true?

The purpose of filling tires with air is to provide them with the necessary pressure to support the weight of the vehicle and ensure optimal performance.
We understand your thoughts. This question seems quite simple, doesn’t it? The rationale behind filling bouncy castles with air instead of using solid steel and polymerized rubber is the same.

In addition to the evident aspects, there are some fascinating principles of physics at play. Being a gas, air has the ability to be compressed to a much greater extent than any solid material. This is particularly significant when you are one of only four wheels supporting the weight of a car that weighs around 1,600 kilograms.

Even lightweight vehicles, such as bicycles, will inevitably cause the wheel to undergo a slight deformation. This is beneficial as it increases the contact area between the wheel and the road, thereby enhancing the vehicle’s traction. Furthermore, using an air-filled tire requires significantly less energy compared to using a solid tire to achieve this deformation. The reason why early adopters of Dunlop’s bicycle tires outperformed their competitors was due to their superior maneuverability at higher speeds, resulting in reduced energy expenditure.

In the field of physics, this phenomenon is referred to as “rolling resistance,” which quantifies the amount of energy consumed by a single tire for each unit of distance traveled. In essence, tires with lower rolling resistance are preferable, and in this case, air-filled tires hold an advantage over solid ones.

That is not solely attributable to their malleability. Additionally, air is lighter than solid rubber, which means that for the same amount of deformation, a more massive object will generate more heat. According to Michelin, this heat loss results in increased rolling resistance.
These advantages become particularly evident when you are driving at a speed of 60 miles per hour (97 kilometers per hour) and suddenly encounter an unexpected pothole. When traveling at high speeds, a sudden and sharp obstacle would result in a significant impact on a solid wheel, which can only absorb the shock in a limited area. In contrast, air would distribute the impact throughout the entire wheel, resulting in a more comfortable ride.

As previously mentioned, your posterior will express gratitude to you at a later time.

Why don’t we substitute the contents of tires with an alternative substance?
Therefore, we have determined the superiority of gas-filled tires over solid ones for most common uses. However, is it imperative for the gas to be air?

According to certain drivers, such as a Formula 1 racer, the answer would be negative. Although there are numerous benefits to using air, there are also a few disadvantages when it comes to inflating your tires with it. One drawback is that air slowly penetrates the rubber over time. Additionally, air is relatively susceptible to changes in heat and moisture. Hence, it is necessary to make periodic adjustments to the tire pressure throughout the year. For instance, if the outside temperature decreases by 10°C (18°F), the tire pressure can decrease by up to 0.14 bars (2 PSI).

For the majority of individuals, this holds little significance. However, if you are engaged in global competitions at velocities of 200 miles per hour (322 kilometers per hour), there exists a more technologically advanced alternative: inflating your tires with nitrogen.

Nitrogen, being a non-humid gas, eliminates the issue of moisture in your tires, resulting in more uniform pressure and compression of the tires. At the high velocities that racers travel, paying attention to those specific details can be crucial for preserving one’s life—a fact that anyone who has experienced a tire blowout at a relatively low speed of 60 or 70 mph (97 or 113 kmph) can only speculate about.

The concept of nitrogen-filled tires, which is commonly associated with high-performance technology, is gradually becoming more popular among everyday drivers on public roads. Therefore, is it advisable for you to spend your entire salary on a set of four N2 tires?

Most not

“There is indeed a reduced rate of nitrogen loss in tires,” states Les Schwab, a tire retailer. However, the degree of improvement is minimal… For individuals driving passenger vehicles, this does not have a significant impact on improving fuel efficiency or reducing tire deterioration.

And that is logical. The composition of air consists mainly of nitrogen, with approximately 78 percent nitrogen and 21 percent oxygen. When filling your tires with nitrogen, the nitrogen content will reach a maximum of around 95 percent N2. “It is never completely certain,” Les Schwab states.

According to the authors, the use of nitrogen in tires will reduce the rate of inflation loss to approximately one-third of what would occur with regular air. However, it is necessary to regularly inspect and replenish the air in your tires approximately every two months in order to maintain the optimal inflation level.

“Additionally, you will incur expenses that exceed the amount you will save on gas and tire wear,” they explain. “It is advisable to incorporate regular tire maintenance into your routine.”

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