Tire Load Index And Range (Ply) Ratings

Both Load Index and Load Range tell you how much weight a tire can carry. Now here, the load range, ply rating, load rating they are all same, so don’t get confused with these terms, they are all old measurement standards. In older days, in order to make a vehicle able to carry more weight, more number of plies were added in their inner construction.

With advancements, the tire don’t have to carry as many plies underneath, so now most of the tire have 2 ply polyester casing cover inside, with 2 steel belts layer on top and a 1 layer of nylon. So Load ratings were introduced which now tells with alphabets, like D , E and so on.

If we take E for example, it means (although the tire actually does not have 10 plies), its inner lower number of layers are as powerful as 6 plies.

Load Range/Rating

There’s a lot of confusion concerning the terminology around load ratings and sidewall ply. Older tires would have a separate specification for resistance to vertical loads, but newer ones don’t. This means that today the load rating of a tire can be cross-referenced with an old bias ply tire’s value for resistance to vertical loads.

Bias ply sidewall load rating was a measurement of how many liners were used in a ply and puncture resistance, but now you can achieve similar results with less no. of plies.

So as 4, 6, 8, and 10 ply construction no longer applies, letters were assigned so users can know how much tire can carry.

Load Range	Ply Rating
C	6
D	8
E	10
F	12

So with load rating C, it means that the tire (with less plies) can carry as much weight as older tires with 6 plies used to carry.

Also note, that these ratings are used for only LT tires, whereas P metric sizes uses and always have been using load index. Let’s discuss these both.

Passenger (P-Metric) Tires

Passenger tires are designed for use on cars and light trucks and these tires are equipped with LL, SL, and XL symbols which are speed rating codes used to indicate the maximum speed at which a tire can safely carry a load under specified service conditions.

SL stands for “standard load” and is a tire with a standard aspect ratio. XL stands for “extra load” and is a tire with a thicker sidewall and higher load carrying capacity than a standard tire.

Light Load

Light load tires, or LL models, have a maximum load pressure of 35 psi. They are “low profile” as they have smaller aspect ratio and stiffer sidewall.

Aspect ratio refers to the height of the tire’s sidewall as a percentage of its width, you can read about it all in tire sizes. For LL models, the aspect ratio is always below 45.

So with these low profiled tires, the vehicle gets to have which can give the vehicle a sportier look and better handling, though it also compromises on comfort a little bit.

Standard Load

Standard load (SL) tires are tires with aspect ratios above 45. And these tires are used with 35 psi max load pressure. They are the most common type of tires out there. So if your sidewalls has nothing on it, consider your tires SL.

With thicker sidewalls, these offer a more comfortable ride and better absorption to road imperfections. Though compared to LL, they are rated with typically lower speed ratings.

But that also means they consume less fuel in comparison, and with less rolling resistance they also get to provide better tread life.

Extra Load

XL (Extra Load) tires are designed to carry a heavier load than standard tires. So they can have a maximum pressure of 41 PSI.

Their reinforced internal structure evens out the weight in a better way, allowing them to carry heavier loads compared to SL tires. That’s why they are commonly used on SUVs, vans, and light-duty trucks (weighing under 1 ton).

Moreover, these tires are generally rated with lowest speed ratings compared to SL and XL, and with heavier weight, they get to have higher rolling resistance, which lowers the fuel economy a little bit.

LT Tires

LT (Light Truck) Tires have “LT” in front of their size specifications. And they are for even more heavier loads compared to XL. So these tires can be used in towing and off-road adventure.

This is because these tire have more powerful inner construction of cords carrying extra steel and reinforcing polymers in them.

These tires are mostly used on off-road tires.

And like discussed above have load ratings of C, D, E and F.

Conclusion

So basically there are 2 different types of tires P metric and LT.

With P metric tires, you get a less stronger inner construction, so these tires aren’t able to pick up as much weight, though they get to offer superior fuel economy and tread life in return.

On the other side, the LT tires get to be more aggressive and offers superior stability whilst carrying a heavy cargo, or even a big vehicle’s weight.

In more simpler words, P metric tires are on-road tires, whereas LT are used off road.

They are also divided when it comes to load range and ratings as the P metric sizes use the newer metric, which is called load index, where they are assigned with a number (written on the sidewalls), and with it you can tell, how much weight a tire can carry.

And with LT sizes, Load rating metric is used which can be cross-referenced with an old bias ply construction as well, that’s why its also called ply ratings.

Here letters are assigned, going from C, to F, and these tell how much weight a tire can carry (which is more compared to P metric, so these tires are used off-road and for towing).