Things Not Everyone Knows About Airplane Tires

What are their sizes, how are they constructed, and why do they need to wear down or partially burn during landing?

What is the size of airplane tires?

At first glance, airplane tires may seem quite small compared to the overall size of an aircraft. However, in reality, airplane tires are significantly larger when compared to standard car tires. For example, the tire set of a Boeing 737 measures 27/7.75-R15 in inches, which translates to a diameter of 685.8 mm, a width of 196.85 mm, and a rim size of 381 mm.

Are airplane tires made from materials similar to car tires?

Construction of an airplane tire by Michelin.

The chemical components are similar. A complete airplane tire consists of four basic materials: rubber, nylon, some special cords, and steel. The rubber used is typically natural rubber, as it has superior technical specifications, such as heat dissipation. However, the structure is formed through a process called vulcanization, with multiple layers including nylon and Kevlar. The technical standards for hardness, durability, and wear resistance are also much stricter compared to standard tire production, including supercars or racing tires.

What gas is used to inflate airplane tires?

The gas inflated into the tires is an inert gas like nitrogen, to minimize fluctuations in tire pressure due to temperature changes. If regular air is used, moisture combined with high temperature and pressure during landing could cause the tire to explode when it reaches its limit. Additionally, inert gases help prevent corrosion inside the rim.

What is the inflation pressure of airplane tires?

PSI stands for Pounds per Square Inch, which measures pressure in pounds acting on each square inch. Reports indicate that airplane tires are inflated to about 200 psi, which is six times the psi of an average car tire. In fact, according to an experiment recorded by National Geographic, the tires of a Boeing 737 can withstand pressures of over 900 psi before bursting.

Why are the grooves on airplane tires straight?

This design prevents hydroplaning or aquaplaning situations that occur when the tire moves over a slippery runway during rain. These straight grooves also enhance grip between the runway surface and the airplane tires, stabilizing direction and assisting with braking. If a tread pattern similar to that typically seen on car tires were used, they would simply break apart under landing pressures.

Furthermore, airplane tires do not require cross grooves or shapes to facilitate directional changes while moving, as seen in other transportation vehicles.

Why don’t airplane tires explode upon landing despite the weight and speed they endure?

• First, the pressure in airplane tires is very high.
• Second, each tire can bear an average load of up to 38 tons, and each airplane may have 14, 22, or 32 tires depending on size and type, so the load is distributed across many tires.
• Third, tires are made from ultra-durable materials and feature a special tread system. These three factors help them withstand heavy loads and operate reliably.

Do airplane tires slide or roll immediately upon touchdown?

Immediately upon touchdown, the tires will slide instead of rolling. The airplane pulls them along the runway until the rotational speed of the tires matches the speed of the aircraft. This is why airplane tires often smoke upon landing, and this process also wears down some of the rubber on the runway. To achieve this, modern anti-lock braking systems designed specifically for aircraft apply and release brakes hundreds of times per second, aiming to minimize landing distance.

Does rubber come off the tires on the runway?

Most tire wear occurs during landing. The rubber on the tires will partially burn until the tires rotate at a speed that matches the aircraft’s ground speed. This produces significant smoke and wears down some of the rubber, leaving it on the runway. Airports often use high-pressure water or chemicals to remove this rubber residue.

How often do airplane tires need to be replaced?

An average airplane tire can perform about 450-500 landings before needing to have its tread resurfaced. A tire can be retreaded up to seven times throughout its lifespan. The replacement process can take anywhere from 40 minutes to two hours.

However, in reality, each tire manufacturer has specific wear criteria to determine when an airplane needs new tires. Occasionally, abnormal issues may arise on the tire’s surface, such as cracks, breaks, or unusual wear, and they may need to be replaced immediately.

Even when not in use, airplanes still require periodic tire replacements. Moreover, external temperature can affect tire longevity, for instance, if an airplane frequently flies over the ocean or lands at airports with high temperatures near deserts, where runways often have a lot of sand.

Are airplane tires expensive?

Depending on the type of aircraft, manufacturer, and other criteria, airplane tires can range in price from several dozen to several hundred or even several thousand dollars each.

Therefore, to know the specific price of a tire in a particular position on the aircraft, you need to take the serial number from the tire and inquire with the airline’s purchasing department. Prices may also vary if you or airlines have long-term contracts with the tire manufacturers.

Do airlines keep spare tires in stock?

Of course. The storage cost of airplane tires looks like the image shown above. Not only tires, but an airline will store many parts of the aircraft, managed closely by a dedicated department. They are responsible for procurement, lending, repairing, and exchanging components for their airline or even for other airlines if collaboration is requested.

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