We know you’ve been asked “how many plies does that tire have?” Or maybe even had a customer use it as a comparison point with their old tires.

If we’re thinking about what actually supports the load of any vehicle, it’s the air pressure in the tire doing the job, and simply put, heavier loads require higher pressures, which require a stronger tire that can handle that pressure.

In the past, we could say the higher the number of plies, the stronger the tire. Today, we have to think of it as the higher the ply rating, or the higher the load rating, the stronger the tire.

Now why is this? As we covered in our last video, in early bias tire construction, the casing, or the main body of the tire was constructed of cotton fabric, with multiple layers, or plies being laid on top of one another. The higher the number of plies, the stronger it got, so that’s what we looked for in a tire.

Technology brought stronger materials into the tire making process such as nylon and polyester, and steel belts came into the scene with radial tires.

The strength of the plies and the tire casings were improved so considerably that fewer plies were required to make a strong tire, but so we didn’t upset the apple cart, we snuck in the word “rating” after ply, and now, in many cases tires with a higher ply rating such as 6 and 8 may in reality only have two or three plies.

The bottom line is that ply rating is used to provide a direct comparison of the strength of a new tire to that of an old. A 2- or 3-ply new tire may be just as strong or stronger than a 6- or 8- ply tire from years ago.

Sharing knowledge with your customers will give them confidence in your recommendations.