Learn How to Apply Tire Load Inflation Tables

Learn How to Apply Tire Load Inflation Tables

At times, load inflation index tables can become confusing and hard to read. Most of the time, load indexes possess different standards based on their manufacturers and companies, so it’s essential to know your way around. But don’t get me wrong–load inflation index tables can be quite beneficial. A typical load inflation index table can be remarkably helpful in a situation where you don’t know how large of a load your car can carry.

Tire Load and Inflation Standards

Load and inflation tables are based on various standards—standards that are essential to know. These standards include The Tire and Rim Association, inc. (TRA) (North America), The European Tire and Rim Technical Organization (ETRTO) (E.U.), and the Japan Automobile Tire Manufacturers Association (JATMA). It’s vital to know the foundations of the standards mentioned because each of them is different.

ISO Metric vs. P-Metric

It’s also essential to know which standard applies to a given tire size, since the load capacity may vary at any inflation pressure value. The TRA created the P-metric standard, while the ETRTO made the ISO Metric standard. Each has a load index, and it’s vital to understand.
The load index is a number associated with the total load a tire can carry at the speed mentioned by its speed symbol in a particular situation. Some tires with the same load index, regardless of size and weight, can carry the same load.
TRA, for example, can have a load index of P225/55R17 95T, suggesting that the vehicle to which this code belongs can carry a maximum load of 1521 lbs. when inflated to 35 PSI.

Single/Dual Load

Some light trucks can have not one, but two load indexes. The first load index would apply to single-tire fitments, and the second would refer to the tires in dual. Once LT tires are fitted in dual assemblies, the load capacity decreases by about 9% of the single load capacity to compensate for the effect of road crown.
Another important thing to note is that P-metric and hard-metric tires can never replace each other. Make sure that any potential replacement has a greater or equal load capacity as the original.

Cold Inflation Pressure

According to what TRA had mentioned, the cold inflation tire pressure is “taken with the tires at the prevailing atmospheric temperatures and does not include any inflation pressure build-up due to vehicle operation.”
This statement suggests that your tire pressure should be regularly checked when they’re cold. It’s easiest to check your tire pressure in the morning, since your car would be parked for the whole night.

Standard Load vs. Reinforced (RD) or Extra Load (XL)

The term “Reinforced” and “Extra Load” both refer to a given tire’s ability to carry an additional load at a higher inflation level. The sidewall of your tire should have one of the two terms, and if it doesn’t, you have standard-load tires.

How to Read and Apply Load Inflation Tables

Below are a few procedures you could use to apply what’s written on a load index table:
Original Equipment
Find the tire’s placard to determine its size and cold inflation pressure.
Identify which standard is used and search for a load index table that is based on that standard.
Find the load capacity for the tire’s size at the recommended cold inflation pressure.
Replacement Tire
Use the right load index table for the replacement tire(s) based on a given standard.
Locate the inflation pressure to which the load is greater than or equal to the original tire.
Inflate the tires to the recommended inflation pressure.
Make sure that you don’t use an inflation pressure that is lower than what the manufacturer recommends.

Load inflation index tables can be difficult to understand, but they’ve already proven to be useful for many drivers out on the road. Hopefully this article taught you something new about load index tables and how to understand them.