What is a Tyre Ply Rating? Has a Ply Rating of a Tyre Lost it’s Significance?

Tyre Ply

The Tyre ply rating is the special marker which lends valuable inputs about the strength as well as the ability of the tyre to bear loads. It actually denotes the makeup of the tyre. It also gives you an idea of the layers of rubber and steel in the tread part as well as the border or wall of the tyre. It could be the same or different.

Tyre construction and ply rating

The tyres are constructed by combining the layers of rubber reinforced with strands of nylon, polyester, any other textile material or even steel. These thin sheets of rubber piled up for making the tyres are called the ply.

The toughness and stiffness of the tyre are directly proportional to the number of plies that make up the tyre. But the ply of the sidewall could be slightly lower to infuse a degree of flexibility.

Ply rating interpretation

Interpretation of the ply rating would be complex as long as you do not understand the way in which it is denoted.

For example, the rating 8 ply is supposed to denote tyres that are made of 8 plies of reinforced rubber. 8 plies in the tread as well as the side wall.

However, if the ply rating is mentioned as 4 plus 2 plies, it has to be inferred that the layers of rubber are 2 on the borders or the walls and 4 on the treads.

What sort of ply rating is good?

As far as the Tyre ply rating is concerned, you can consider the high ply rating to be synonymous with greater load bearing strength. The greater the number of plies, stronger and tougher are the tyres.

At the same time, you must also be aware that 6 or 8 ply rating in modern, technology-driven manufacturing processes need not necessarily denote the number of plies of rubber.

They may also denote the construction of the tyre. It may be an indicator of the fact that the tyre has the strength to handle the same load as that of a 6 ply or 8 plies tyred vehicle.

Ply rating graph

The load range associated with the corresponding rating of ply is depicted in the graph as follows

PLY RATING LOAD RANGE
A 2
B 4
C 6
D 8
E 10
F 12
G 14
H 16
J 18
L 20
M 22
N 24

You will note that the Tyre ply ratings of the ascending letters can carry heavy loads. They will be strong and can also withstand high inflation pressures.

Load range and ply rating compared

The tyres feature alphanumeric symbols. Load range B indicates that the car can carry loads at a maximum inflation pressure of 32 psi.

The C, D, and E range are meant for lightweight trucks. This means it is comparatively stronger than the load range B tyres. It goes to show that the desired load-bearing capacity is achieved by making changes in the strength of the casing.

Load range designations

The modern manufacturers of tyres designate the load range symbols on the side walls. The designations in the sidewall include,

  • Passenger cars– The fall under the standard load category and do does not carry any branding on the side walls.
  • Light load– It is depicted by the sign LL on the side wall. It can carry the maximum load designated for the type at 35 PSI.
  • Extra Load – It is indicated on the sidewalls as XL and is believed to have a load pressure of 41 PSI.
  • Light truck tyres– They contain the sign LT followed by an alphabet in the ascending order where the alphabet B refers to 4 ply rating at 35 PSI and 6  Tyre ply rating at 50 PSI.
  • Trailer service tyres- They are indicated by the sign ST and is almost the same as the light trucks with respect to the alphabetical rating system. Nevertheless, the tyre size and the high air pressure may be considered as suitable for bearing loads that are rated as heavy.

Load index and overhauling- the significance

When you are overhauling the vehicle and want to change either the size or the type of tyre, the load index will be a useful index.

You should ensure that you only replace a tyre with either an equal or greater load index than the one installed in your vehicle at present.

It is also important to ensure that the rated load capacity of the tyre is sufficient to bear the gross axle weight of the vehicle.

Fuel efficiency, better control over acceleration, braking as well as better driving experience can be achieved by choosing the right ply or load bearing index.

Is ply rating relevant even now?

No, Tyre ply rating actually refers to the strength of the tyre based on the number of thin layers used to make it. It was relevant in those days as piles of cotton or even nylon were used in the construction.

But with technological advancements and the use of steel ply materials, ply no longer stands for the number of layers in the making of tyres. Therefore, the ply number has lost its significance.

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