What is the difference between load range and load index and how does the tire's ply rating determine what tire you should buy? Well, your vehicle will have specific minimum requirements for each of these ratings and guidelines. Let's jump into each one of these ratings to understand how these simple letters and numbers add up to keeping you safe on the road.
Load Range and Ply Rating
There are a few different classifications tire experts use to discuss a tire’s ability to hold air pressure and carry weight. You’ll find one of these classifications, the load range, listed on the tire sidewall represented by a letter. This letter code gives you a comparative idea of the tire’s toughness; helping you understand how much air your tire can hold, how much weight it can carry and it provides a relative measure of the tire’s durability. Tires with a higher load range can carry heavier loads.
Load range is based on an older measurement called ply rating. All tires are constructed of rubber and cord layers referred to as “plies”. Historically, more plies gave a tire a larger load carrying capacity, so manufacturers would count the plies and use this number to denote carrying capacity.
However, modern tire construction uses fewer, stronger plies. Therefore, load range simply defines the tire’s toughness and maximum allowable air pressure, as opposed to specific information about the actual plies being used. For example, a “C” load range indicates that a tire is equivalent to a 6-ply construction tire. This tire isn’t actually built with 6 plies, but rather one or two plies of equivalent strength.
Using this same example, when it comes to load range, you may see these indicated as "C1" or "C2". To simplify this even further, the letter "C" still indicates the load range but the number after it designates a difference in max load carrying air pressure. "C1" and "C2" are both 6 ply rated, but C1 has a max air pressure of 50 PSI and C2 has a max air pressure of 35 PSI. This holds true for other ply ratings too. See chart below.
Check the tire sidewall to find the letter that indicates the load range. Tires on a sedan, coupe, crossover or minivan are usually unmarked because they have a standard 4-ply rating and do not require higher load carrying abilities. However, you may find these tires marked as Standard Load (SL) or Extra Load (XL or Reinforced). Both have a 4-ply rating, but the Extra Load can support additional load at up to 42 PSI while the Standard Load is 36 PSI. If your tires indicate higher max air pressures than the max load carrying air pressure of the tire, a tire expert may need to weigh in to make sure the tire being used can handle the weight requirements of the vehicle.
Check our chart to see the load range, ply rating and the max load carrying air pressure.
|Load Range and Ply Rating|
|Load Range||Ply Rating||Max Load Carrying Air Pressure|
|Standard Load (SL)||4||@ 36 PSI|
|Extra Load (XL)||4||@ 42 PSI|
|C1||6||@ 50 PSI|
|C2||6||@ 35 PSI|
|D1||8||@ 65 PSI|
|D2||8||@ 50 PSI|
|E1||10||@ 80 PSI|
|E2||10||@ 65 PSI|
|F1||12||@ 95 PSI|
|G||14||@ 110 PSI|
Load Index and Load Carrying Capacity
Load index is used to further describe a tire’s carrying capacity. The load index explicitly indicates how much weight a tire can carry. To find your tire’s carrying capacity, look for the load index number on the sidewall.
The load index number indicates a tire’s carrying capacity when inflated to maximum load sustaining pressure. It corresponds to another number in an index, which tells you how many pounds of weight the tire can carry.
Find your tire’s load-bearing capacity by checking our load index below. Most cars and light trucks have load index values ranging from 70-124.
|Load Index and Carrying Capacity|
|Load Index||Carrying Capacity (lbs)||Load Index||Carrying Capacity (lbs)||Load Index||Carrying Capacity (lbs)|
If you have any questions about load range or load index or what tire might be the right option for you, please give us a call or stop by your local store.