Ply rating measures how strong a tyre is and how much weight it can safely support. This article explains what the different ply letters mean, how they affect handling and durability, and why it’s vital to match the correct rating to your vehicle.
The ply rating measurement on a tyre has changed over the years. While it still represents the same underlying feature of a tyre, the way it is interpreted and read has changed.
Once upon a time, ply rating literally meant the number of layers that a tyre was constructed from.
Nowadays, the manufacturing methodology for tyres has changed – though ply rating is still used as the measurement for how strong a tyre is. The difference is that physical layers are no longer counted, rather the ply rating is simply a unit of measurement.
What Does the Ply Rating Look Like?
The ply rating for a tyre is communicated as a single letter.
This letter then corresponds with the load capacity that the tyre can carry. The overall weight of the vehicle is spread over (on average) four tyres, meaning that the load capacity of all four tyres must total an amount less than or equal to the weight of the vehicle with its regular passenger load.
Look at it this way.
A ply rating of C equates to a load capacity which is lower than a ply rating of E.
This is because, on a standard chart, A equates to a 2 ply rating, and the alphabet then follows in increments of 2 ply. So C equals 6 ply, and E equals 10 ply.
NOTE: A passenger car will usually boast a ply rating of 4 (‘B’) while trucks and vans tend to start with a ply rating of 6 (‘C’) and increase from there depending on the size of the vehicle.
Why is Ply Rating Important?
Ply rating is an important part of the tyre size calculation, because it ensures that the tyres you choose are suitable for the vehicle you drive.
If the tyres are not strong enough to hold the weight of the vehicle, you increase the risk of punctures and blowouts. You will also find that performance and handling are negatively impacted, with insufficient tyre strength sometimes warping the shape of the tyres and causing them to move and react at a sluggish pace.
Suffice to say, understanding how to match ply rating with your vehicle needs is an important part of safe maintenance.
