Made from a variety of different materials and components, tires manufactured today are a lot more sophisticated than the tires used in vehicles more than fifty years ago.
However, if you’re trying to find the most suitable tire for your vehicle, you may be wondering – what are tire plies, and what do they do? Keep reading to discover what I learned through my research!
What Are Tire Plies?
Tire plies are layers in the tire’s inner section that are made of strong materials such as nylon, polyester, and steel. Plies improve the structural stability and strength of tires, allowing them to carry greater loads. Generally, tires are equipped with radial or bias plies.
If you want to learn more about what ply rating is and how to identify it, whether higher ply tires are better and more, keep on reading for more useful facts and tips!
What Does Ply Mean On A Tire?
Ply refers to the layer of sturdy materials like steel, polyester, and nylon inside tires that are encased inside tough rubber compounds.
Note that you cannot see the ply by looking at the tire from the outside, since these layers run in the inner section of the tire beneath the tread.
Who Invented Plies?
Plies were first developed by the Michelin brothers and were used to provide additional support and resilience for tires to ensure a more smooth ride.
Over time, the use of plies has become a central part of tire manufacturing due to the structural benefits and stability that they bring.
What Types Of Plies Do Tires Have?
Tires are commonly manufactured with two types of plies, Radial Tire and Bias Tire plys, and the details for these plys are as follows:
Radial Tire Ply
Radial plies run perpendicular to the direction of travel from a vehicle, and therefore they offer excellent rolling resistance, improve traction and make vehicles more fuel-efficient.
As well, these properties make radial-ply tires suitable for passenger vehicles, with most high performance, touring, and all-season tires manufactured with radial plies.
Bias Tire Ply
These types of plies run diagonally (in a cross pattern) to the direction of travel, unlike radial plies that are perpendicular.
This design compromises the rolling resistance but makes the tires sturdier and capable of withstanding a greater load.
Therefore, tires with bias plies are commonly manufactured for use in heavy machinery such as tractors and trucks.
What Do Plies Do?
The most important job of plies is to maintain the circular shape of an inflated tire and the integrity of its structure when it’s being driven on a smooth or rough surface.
This, in turn, protects the vehicle’s suspension from getting damaged due to large shocks that are produced while driving on rough or uneven terrain, or due to road hazards and accidents.
Additionally, plies also make it possible for vehicle owners to repair their damaged tires instead of having to replace them altogether.
What Is The Ply Rating?
The ply rating of a tire determines the maximum amount of weight it can carry if it’s fully inflated.
In previous years, the ply rating was equal to the number of ply layers a tire contained, since plies used to be made of cotton.
For example, a tire could be rated 2-ply, 4-ply, 6-ply, 8-ply, 10-ply, and even 12-ply with the toughness and strength of the tire increasing with the number of plies.
However, in modern times, plies are manufactured from stronger materials that provide a similar level of sturdiness with fewer layers.
Therefore, tire manufacturers now specify the ‘load range’ instead of the ply rating to indicate the maximum load a tire can be subjected to.
The load range consists of the ratings A, B, C, D, E, and F, with A roughly representing the strength of 2-ply tires and F representing the strength of 12-ply tires.
Tires used in passenger vehicles are typically rated either B or C, the equivalent of 2 to 4-ply.
For further classification, manufacturers assign one of three categories to these tires – standard load, light load, and extra load.
As the names suggest, most tires are designated as being able to withstand ‘standard load,’ with ‘extra load’ tires having the capacity to bear even heavier weights.
In contrast, tires used for light trucks come with ratings of B, C, D, E, and F, i.e. there is a wide variety of tires available for light trucks that can carry vastly different loads.
How Do You Determine Tire Ply?
It’s easy to determine the ply or load rating of any tire since the rating is etched into the sidewall of every tire by the manufacturer.
Tires used in passenger vehicles will typically have one of three abbreviations – ‘LL’ for Light Load, ‘SL’ for Standard Load, and ‘XL’ for Extra Load.
As for tires used in light trucks, you should look out for the abbreviation ‘LT’ followed by one of B, C, D, E, or F, which will tell you the load/ply rating of the tire.
However, in case the etching on the sidewall is no longer visible due to wear or damage, you should contact and visit a professional mechanic to assist you in identifying the rating.
How Many Ply Is A Standard Load Tire?
A Standard Load (SL) tire will have a load range of B, which corresponds to a 2-ply rating and a maximum allowable inflation pressure of 35 psi.
Note that the 2-ply rating does not mean that SL tires have 2 plies, it merely indicates that the tire is as strong as older tires that actually had 2 plies.
This difference, as mentioned earlier, is because modern tires become considerably stiff and strong with a very limited number of plies due to the use of advanced materials.
Is A Higher Ply Tire Better?
Whether a tire with a higher load rating is better for you or not depends on the kind of vehicle you own and the kind of work your vehicle has to do.
Keep in mind that the higher the load/ply rating, the stiffer and stronger the tire will be, giving it the ability to bear heavy loads without blowing out.
However, at the same time, stiffer tires often lead to more discomfort while driving the vehicle.
So, if you regularly drive on rough and rocky terrain, or you drive a truck or trailer that has to carry heavy weights and tow other vehicles, you should go for tires with a high ply rating.
Generally, a higher ply rating will give you the peace of mind of knowing that your tires will not blow out and leave you stranded.
On the other hand, if you mostly drive on smooth roads and your vehicle does not carry extra weight, you should opt for tires with a moderate load rating so that you have greater comfort.
What Ply Tires Should A Truck Have?
A truck that has to carry heavy loads such as farm animals, boats, bikes etc. (or has to tow other vehicles) should have a load rating of D, E, or F.
Overall, this will ensure that the tires can reliably support all the stress and weight of the load being carried without blowing out.
Do High Ply Tires Affect Gas Mileage?
High ply tires do not affect gas mileage, even though they weigh more than tires with lower ply ratings (because the rolling resistance of tires does not change with weight).
Instead, if you replace your vehicle’s tires with ones that are larger in size (height), your gas mileage will drop by a small amount due to the increased rolling resistance.
Therefore, as long as the size of your tires remains the same, getting higher ply tires will not negatively affect the gas mileage of your vehicle.
To learn more, you can also see our posts on what are XL tires, how much do monster truck tires weigh, and if tires affect gas mileage.
Tire plies are layers made of steel, polyester, nylon, and other strong materials that are covered with rubber and added to the inner section of tires to make them stronger.
Although tires were assigned a ‘ply rating’ in the past, modern tires are given a ‘load range’ to indicate the relative strength and stiffness of the tire. I
f you drive around in rough terrains, tow other vehicles frequently, or transport heavy loads, you should use tires with higher ply ratings.