I decided to write this article after I had worn the rear tyre on my bike down to the carcass and it reminded me of an old TV advertisement showing the dangers of mixing cross-ply and radial tyres on the same axle. The result could be circular driving with ends swapping direction!
Radial tyres were first developed by Michelin in 1946 to improve the tyre structure. They got to the market in Europe in 48 but it wasn’t until the late 60s that they reached the US market. Up until then, Cross-ply tyres were the normal type of car tyre but they had some inherent problems compared to the new radials.
In 1898 Goodyear developed a vulcanised rubber tyre by adding in belts of rubberised fabric to strengthen the tyre before the tread was moulded. Each belt was laid in an alternate diagonal pattern of about 30 – 55 degrees. These diagonal patterns lead to the name cross-ply. Incidentally Charles Goodyear who invented vulcanised rubber was not connected to the tyre company. It was named in honour of him though.
In the early years, tyres had cord belts dipped in rubber, then Goodyear introduced rayon belts before improving them further to nylon cords. The tyres also had tubes as well. By 1954, Goodyear had advanced to tubeless as they are today. Then in 59, steel belted tyres were introduced. The structure of the tyre meant that there was high friction with the tyre not fully making contact with the road and the belts and sidewalls shared the same underpinnings so there was a fair bit of deformation of the tyre.
What Michelin did was to make the belts directional on the tyre i.e. radial, which meant that the tyre squatted on the road providing reduced friction and much higher grip. The reduced friction improved fuel economy and the increased grip increased steering ability. In addition, the tyre had improved tyre wear which meant that although they were more expensive to manufacture, they lasted longer.
Radials are now the normal tyre and in recent years much more research has been done to ensure a better tread pattern and a better carcass structure with different compounds of rubber for different applications. For example, the Bridgestones on my Honda have a softer compound than a tyre designed for a family wagon.
Tyres are an important piece of the vehicle and care should be taken to look after the tyres as they will help to reduce fuel usage and are the only pieces of the car touching the ground, so tyres with good grip will help under braking and acceleration.