Since its development and patent by the Michelin tyre company on June 4th, 1946, the radial tyre has been a key part of the car tyre industry.
In fact, many would say it helped accelerate the automotive industry. So, just what are the advantages of this invention, compared to alternative tyre designs?
What Are radial tyres?
Radial tyres get their name from the method of applying elements to the carcass layer. This layer is arranged radially, away from the tyre’s front axis.
This carcass layer consists of thin wires and fabric, arranged in a series of simple arches. It is also known as the tyre body, as this forms the basis of the tyre’s main support.
You can find information indicating a radial tyre on its side.
Radial tyre beginnings
The first tyre with a structure reminiscent of today’s radial tyre was created in 1939. This was developed by two British men - Gray and Sloper - working for the Palmer Tyre Company. This solution was not accepted, so this early design did not go on to enter serial production.
Another variant, the so-called “fly trap”, was designed in 1929 by Marius Mignol, an engineer for Michelin. The sidewalls of this tyre were replaced with arches made of steel, which were placed every 1.5 cm. This design also included the installation of a special reinforced tyre tube.
This design offered two basic advantages:
the tyre was heated to a lesser extent,
driving the car was more stable.
The concept was widely recognised and was further developed until 1946, when it was superseded by the launch of the radial tyre.
the internal structure of the first radial tyres - the so-called “fly trap”.
The launch of radial tyre production
One of the first ‘true’ radial tyres, the Michelin X tyre (originally called the 185-400 SP) was launched in 1949. The patent for radial tyres, including the steel belt, was granted in the same year.
The subsequent history of the radial tyre was as follows:
1951 - The Pirelli tyre company develops its own radial tyre, called the Cinturato, with a cap pile made of viscose.
1952 - The first radial tyres for trucks appear on the market
Mid 1950’s - Other companies, notably Continental, Dunlop, Firestone and Uniroyal, launch their own radial tyre products.
1979 - The first BIB X radial tyres, designed for use on agricultural machines.
1981 - Radial aircraft tyres are designed for the Dassault Mirage III aircraft
1984 - The first radial motorcycle tyre is designed, but not yet sold
1987 - Radial motorcycle tyres enter production.
1970 - A global diversity in tyre choice begins to be observed. 98% of US cars include bias or belted tyres, while 97% of tyres in France, as well as 80% in Italy, are radial.
The process for popularising the radial tyres in America started much later than it did in Europe. These products become much more popular after Ford, increasingly dissatisfied with American bias tyres, selected the Michelin X model to be the factory fitted tyre for the Lincoln Continental Mark III in 1966.
Michelin X - the first serially produced radial tyre.
Similarly, the oil crisis in the 1970s also provided another reason to accelerate the ‘radialisation’ of the United States. This was thanks to the lower maintenance costs of radial tyres, making them easier to produce and maintain.
Radial tyre vs. bias tyre
While you can still find bias tyres, especially for specialist vehicles or replacement vintage tyres, it’s safe to say the radial tyre is much more appreciated when it comes to consumer cars, as well as the likes of van tyres. Why is this?
In a bias tyre, the carcass includes several layers of fabric, arranged alternative in two directions at various angles (usually less than 90 degrees). The exact number depends on the intended use and the tyre size.
Other bias tyre variants include a belt, but it is these are often referred to as belted tyres, to distinguish them as separate products.
In a radial tyre, on the other hand, the carcass plies at 90 degrees, relative to the tyre’s front axis. The reinforcement belt is used at the face of the tyre. This is a cord layer, made from steel in the vast majority of cases. This arrangement of the carcass helps to improve the flexibility of the tyre sidewall, while the belts themselves ensure better tread stiffness, improving the car’s behaviour while driving on a bend. This also increases the surface area between the tyre and the road.
Advantages of the radial tyre as compared to the bias tyre:
Ultimately, there are a number of key benefits that make radial tyres more useful than bias options:
Improved traction when accelerating, braking or turning
Less heat emissions
Lower rolling resistance
Resistance to damage at higher speeds
Overall, it can be said that the invention of the radial tyre has allowed tyres to meet the requirements set by a quickly developing automotive industry, enabling further development across the entire sector.
More durable tyres allows car designers to make faster cars with more demanding parameters, in turn encouraging tyres to create designs able to meet and exceed these limits. The radial tyre as a key step in this process, enabling the industry to get to where it is today.
Of course, there are other tyre options to consider, including run-flat tyres and reinforced tyres. Yet many of these still incorporate the key radial design that has become popular among tyre designers, for some very good reasons.