The radial tyre is such a common place now that almost no one gives a second thought to it. Just jump on almost any bike these days and it would most probably be rolling on radial tyres. Even riders who moved up from mopeds do not question what they are.

The radial tyre, especially for motorcycles, is something fairly recent, compared to when the pneumatic tyre (tyre filled with air) was invented.

The first pneumatic tyre

It all starts with the first pneumatic tyre. Do remember that tyres were just solid wooden or metal wheels prior to this!

Contrary to popular belief, the patent for the pneumatic was lodged by Scottish inventor, Robert William Thompson in 1847, instead of John Dunlop. His invention, however, did not make it to production.

But it was John Dunlop, a veterinarian, who created the first working pneumatic tyre in 1888. He invented it for his 10-year-old son who complained of headaches after riding their bicycle fitted with wooden wheels. 

A pneumatic tyre means there is a layer of air inside the tyre. That air provides elasticity and hence comfort. Adjusting the air pressure adjusts comfort, and also performance. It has to be said that the early pneumatic tyres were glued to their wheels to prevent the air from leaking and the pressure was not adjustable like in modern tyres.

Radial vs. bias-ply

Early tyres were essentially bias-ply until the advent of the radial tyre.

Bias-ply (also known as cross-ply) describes the plies that form the body the tyre being laid diagonally from bead to bead. Subsequent plies are laid on top at opposing angles, forming a criss-cross pattern (hence the name cross-ply). This allows the tyre to flex easily hence greater comfort. However, this quality was also the main disadvantage of this type of tyre, as it causes increased rolling resistance (takes more effort to get going), together with less traction and control at high speeds (the tyre deforms). Bias-ply tyres generally could not withstand the high centrifugal forces at high speeds, leading to blowouts.

On the other hand, a radial tyre utilizes ply cords that extend from bead to bead and parallel to each other, usually around 90-degrees to the tyre’s travel, instead of diagonally across like in bias-ply tyres. The plies are held in place by stabilizer belts that run just beneath the tread. The advantages of radial tyres are numerous including longer tread life, better steering control, improved fuel economy due to less rolling resistance, and better grip.