Nowadays, radial-ply tyres are used on most cars while traditional diagonal tyres are rarely used. So what are radial-ply tyres and diagonal tyres? What are their advantages and disadvantages? Now let's talk about it.

First, let's focus on the structure of the tyre. The carcass of a tyre can be roughly divided into three layers: buffer layer, belt ply and cord ply. The cord ply refers to the cloth layer composed of rubber-coated parallel cords in the carcass, which is the skeleton of the carcass and supports all parts of the tyre casing. According to the different arrangement of carcass ply cords, tyres are divided into diagonal tyres and radial ply tyres. As for the side signs, "R" stands for radial-ply tyres, and "D" or "一" stands for diagonal tyres.

The so-called radial ply tyre refers to the tyre whose inner cord weave arrangement direction forms an angle of 90 degrees with the centre line of the tread, which is similar to the meridian on the globe. It was invented by Michelin in 1946. The crown and sidewall of the radial-ply tyre are relatively independent. Steel wire layer is usually added to the crown to increase strength and enhance puncture resistance. Therefore, the crown of the radial-ply tyre is thicker. According to the different materials used in the cord ply, it can be divided into three types: all-steel radial-ply tyre, half-steel radial-ply tyre and all-fibre radial-ply tyre.

Radial ply tyres contain the following advantages:

1. The crown and sidewall of the radial-ply tyre are relatively independent with thick crown, hard belt ply, large ground contact area, good adhesion performance and small unit grounding pressure. The load is evenly distributed, reducing the slip distance and increasing the mileage of the tyre.

2. Harder rubber can be used as tread material in the crown part. With a belt ply made of steel wire inside, radial-ply tyre is with good wear resistance and puncture resistance.

3. Due to the small number of plies and small friction between them, the rolling resistance is small, improving the fuel utilization rate of automobiles.

4. Because of the fewer plies, thin sidewalls and soft carcass, the radial elasticity and damping performance are excellent, which can make the car ride smoothly and comfortably and extend the service life of automobile parts.

5. Due to the small number of plies and small friction between them, the tyre temperature rises slowly and drops quickly, which can meet the demand for high-speed driving of automobiles. 

The main disadvantage of the radial-ply tyre is that the tyre side is thin, which may cause lateral deformation, leading to slightly poorer lateral stability. It also requires high manufacturing technology and high cost.