Most of us don’t give our tires much thought apart from when they need to be changed. But do you know what tires are on your automobile or even consider what is a radial tire?
We’re going to look at these vital elements of our vehicles and learn what a radial tire is, how it’s made and if it is better than a non-radial tire.
What Is A Radial Tire?
A radial tire is designed in a particular way, and it is this design that gives the tire its name.
In these tires the cord plies are arranged so that they spread radially from the center of the tire, at 90 degrees to the direction of travel.
They have been the standard vehicular tire since 1976 after Consumer Reports in 1968 found the design to be superior to other tire designs.
History Of The Radial Tire
Although the designs of the first radial tires were patented in London and San Diego within two years of each other in the early twentieth century no actual tires were created.
It wasn’t until Michelin, the French tire manufacturer designed, patented, developed and popularized the radial tire that the world came to know what they were.
The original radial tire by Michelin was created in 1946. As the company owned Citroen the automobile manufacturer it was able to introduce the new design very quickly.
Six years later Michelin introduced a radial truck tire.
Because of the advantages in fuel economy and durability the radial tire technology spread throughout Europe in the 1950s and 1960s.
Then in 1968 the prominent American magazine Consumer Reports announced the benefits of the radial tire to US auto owners.
By 1970 Ford Motor Company had produced the first US made automobile with radial tires as standard. These were Michelin tires on a Continental Mark III.
How Is A Radial Tire Made?
The reinforcement in a tire comes from a series of plies of cord. Plies are the internal layers that make up most of the inner workings of a tire.
Without that inner strength and reinforcement the tire would be weak and flexible.
The system of cords that gives the tire its shape and strength is known as the carcass. For the last fifty or sixty years tires have been made of a carcass of cords of steel, polyester or other materials.
This is inlaid with multiple layers of rubber.
Radial tires have all of the cord plies running at 90 degrees to the direction of travel. This prevents the plies rubbing against each other as the tire flexes thus maintaining the tire’s rolling friction.
These radial cords alone are not sufficient to maintain the rigidity of the tire on contact with the ground. For this reason, the tire is surrounded by belts of steel, polyester or Kevlar that run closer to the direction of travel.
This system separates the tire carcass into two separate systems. The sidewall radial cords give flexibility, ride comfort and a spring-like characteristic. The rigid belts reinforce the tread area of the tire.
Radial Tires Vs Bias-Ply Tires
As we have seen radial tires are constructed so that the plies run perpendicular to the direction of travel.
This delivers a smoother ride and less heat build up in the tire. It also means there is more flexibility in the sidewall of the tire.
A bias-ply tire is made by laying the plies laid out diagonally. This means that the sidewall is not as flexible in a bias-ply tire.
These tires are typically made from nylon cords which are layered, creating plies that are extended diagonally.
This kind of tire will have the same structure in the sidewall as it does in the tread. Every consecutive layer in a bias-ply tire is laid in the opposite direction to the previous one. This forms a criss-cross pattern.
The stability of a bias-ply tire is created by the addition of more layers. This system makes a very durable tire which is highly resistant to punctures and these tires are often used in off road vehicles and farm machinery.
Advantages & Disadvantages Of Radial Tires
Advantages
The main advantage of radial tires is their durability and maneuverability. The tread protects the interior of the tire and ensures high grip and traction.
The flexible sidewall and the layout of the plies ensures a comfortable ride as there is more stable contact with the road surface. Meanwhile the steel belts provide stiffness to the tread.
A thick shoulder also provides protection against damage and shock due to the addition of a bead filler and wires which hold the tire to the rim (see also ‘How To Clean Chrome Rims‘).
As there is less rolling resistance the radial tire gives a vehicle greater fuel efficiency and so reduces fuel consumption.
There is also less heat generated in a radial tire as it has a chafer that protects the plycord from friction of the rim flange and the bead rubbing. This extends the life of the tire.
A radial tire also produces less vibration.
Disadvantages
Comparing a radial tire with a bias-ply tire shows there are some disadvantages to this design.
Low lateral stiffness tends to cause the radial tire sway to increase as the speed of the automobile increases.
A radial tire is vulnerable to when the vehicle is overloaded or if the tire itself is under-inflated. In these circumstances the tire wall will bulge and subsequently cause damage or a puncture.
Bias-ply tires are better than radials for construction and farm vehicles, trailers and off-road vehicles as they conform more readily in the tread. They are also cheaper than radial tires.
Final Thoughts
Radial tires are standard on all cars in the US and have been since 1976 due to their acknowledged superiority over other designs.
While we mostly take our tires for granted it is good to know how they are made and what performance we should expect from them.
We hope this guide to radial tires has been helpful and informative.