Tyres come with a ply rating. Today we are going to explain a bit what tyre ply and ply rating is.
With the passage of time, there have been great improvements in the science and alchemy behind the manufacturing of tyres. Tyres are not just one blob of rubber carved in a circle. They are constructed with layers of rubber and cords of polyester, steel, or other textile materials, inlaid with several layers of rubber and then fused together as a one piece. And those thin layers are called ply.
The ply rating is how many layers of rubber is on the tyre. A common one is 8 ply meaning it has 8 layers of rubber. Some tyres have same number of ply all around the tyre, meaning if there are 8 ply in the tread part of the tyre, its side wall will be 8 ply as well. But there are tyres that have different tread vs sidewall ply. For example, regular car and light tyres have 4 plies under the tread and only 2 on the sidewalls, hence a 4+2 ply tyre. Often there are more plies under the tread area of the tire than the sidewall. This allows for strength while keeping sidewall flexibility.
Higher the number of ply, tougher and stiffer the tyre. A higher ply rating number indicates a greater load range for the tyre. One important thing about the ply rating is that if the tyre says 6 ply rating, it doesn’t necessarily means it has in fact six layers of ply but it indicates that the tyre has same strength as of 6 ply. Take a look at the graph below: