The AT3 E-Load rating tells you the maximum weight one tire can safely carry at a specific air pressure

The Discoverer AT3 is a light-truck tire made by Cooper Tire. The "E-Load" designation refers to a load index — a two or three-digit number that corresponds to a specific weight capacity. For the AT3 line, an E-Load rating means that tire can carry a defined maximum weight when inflated to its rated pressure. This matters because using a tire rated for less weight than your vehicle actually puts on it can cause overheating, premature wear, and blowouts.

Load ratings exist because different vehicles put different amounts of weight on each tire. A full-size pickup truck with passengers and cargo loads each tire more heavily than a sedan. Tire manufacturers test tires to breaking points and assign a load index based on that testing. The E-Load is one step in Cooper's rating system for the AT3 — other variants carry different load indices.

You need to know your vehicle's actual load requirement to choose the right tire. That number comes from your vehicle's door jamb label or owner's manual, not from the tire itself. If your vehicle requires a load index higher than E-Load, the AT3 E-Load is not the right tire for your vehicle, even if it fits the wheel size.

Key Takeaways

  • The E-Load rating is a load index that specifies the maximum weight one AT3 tire can carry when inflated to its rated pressure.
  • Your vehicle's load requirement is printed on a label inside the driver's door jamb and in your owner's manual — that is where you find what load index you need.
  • Choosing a tire with a load index lower than your vehicle requires can lead to tire failure, overheating, and unsafe handling.
  • The AT3 comes in multiple load ratings, so other variants may work for your vehicle if the E-Load does not.

Where to find your vehicle's load requirement

Open your driver's side door and look at the door jamb — the vertical surface where the door latches. You will see a label with tire and loading information. This label lists the recommended tire size and the load index your vehicle needs. The load index appears as a number, often followed by a letter (like "104H" or "110S"). The number is what matters for load capacity; the letter is the speed rating.

If you cannot find the door jamb label, your owner's manual contains the same information in the tire or specifications section. Some vehicles also print it on the fuel door or inside the glove compartment. Write down the load index number before you shop for tires.

How load index numbers work

Load indices run from 75 to 150 and higher, with each number representing a specific weight capacity in pounds. The relationship is not linear — index 100 does not mean 100 pounds. Instead, each number maps to a standardized weight according to industry tables. For example, a load index of 104 corresponds to 1,984 pounds per tire; index 110 corresponds to 2,337 pounds per tire.

The E-Load designation on the AT3 refers to a specific load index within Cooper's naming system. To know the exact weight capacity, you need to check Cooper's specifications for the AT3 E-Load in your tire size. Tire retailers and Cooper's website list this information. Do not assume two tires with the same name carry the same load index — different sizes of the same model can have different indices.

Why load rating matters for safety and tire life

A tire rated for less weight than your vehicle places on it will flex more than it should. That extra flexing generates heat inside the tire. Over time, heat breaks down the rubber and the internal structure, leading to bulges, cracks, or sudden failure. Underrated tires also wear faster and can make your vehicle handle poorly, especially when braking or turning.

Overloading a tire is one of the leading causes of tire blowouts on highways. The risk is highest when your vehicle is fully loaded — passengers, cargo, and fuel all add weight. If you regularly carry heavy loads, you may need a higher load index than your vehicle's minimum requirement.

Matching tire size, load index, and speed rating

When you replace tires, you need to match three things: the tire size (like 265/75R16), the load index, and the speed rating. Your vehicle's door jamb label tells you the minimum load and speed rating you need. You can choose a tire with a higher load or speed rating — that is safer — but not lower.

The AT3 comes in many sizes and load ratings. If the E-Load version does not meet your vehicle's requirement, Cooper makes other variants of the AT3 with higher load indices. A tire retailer can cross-reference your vehicle's requirements and show you which AT3 sizes and ratings will work. Mixing load ratings on the same vehicle is not recommended — all four tires should have the same or higher capacity than your vehicle requires.

Reading the sidewall to confirm load rating

Once you have a tire in hand, the sidewall prints the load index and speed rating together, usually near the tire size. You will see something like "104H" or "110S" stamped into the rubber. The number is the load index; the letter is the speed rating. Check this against your vehicle's requirement before installation.

The sidewall also shows the maximum air pressure for that tire, listed as "Max Pressure" or "Max PSI". This is the pressure at which the tire reaches its rated load capacity. Your vehicle's door jamb label may specify a lower pressure for normal driving — follow your vehicle's recommendation for everyday use, not the tire's maximum.

What to do if the AT3 E-Load does not fit your vehicle

If the E-Load rating is lower than your vehicle requires, you have two options. First, check whether Cooper makes a higher-rated version of the AT3 in your tire size. Second, consider a different tire model altogether. Many manufacturers make light-truck tires in a range of load indices, so you have options beyond the AT3.

A tire retailer can help you find alternatives. Bring your vehicle's load requirement and tire size, and they can show you which tires meet both specs. Do not assume a tire fits just because it matches your wheel size — load index is a separate requirement that must also match.

Frequently Asked Questions

Can I use a tire with a higher load index than my vehicle needs?

Yes. A higher load index is safer and will not harm your vehicle. You may pay slightly more for the higher-rated tire, but there is no downside to having extra capacity. Never go lower than your vehicle requires.

What happens if I put an E-Load tire on a vehicle that needs a higher index?

The tire will overheat and wear prematurely because it is flexing more than it was designed to. Over time, this causes internal damage, bulges, and potential blowouts. It also affects handling and braking. Do not use an underrated tire.

Is the load index the same for all sizes of the AT3?

No. Different tire sizes within the same model line can have different load indices. A 265/75R16 AT3 E-Load may have a different index than a 285/75R16 AT3 E-Load. Always check the sidewall or manufacturer specs for your specific size.

Where do I find the load index on my vehicle's door jamb label?

The label lists recommended tire size and load index together. Look for a number and letter combination like "104H" or "110S". The number is the load index. If you cannot read it clearly, your owner's manual repeats this information.

Can I mix different load ratings on my vehicle?

It is not recommended. All four tires should have the same load rating or higher. Mixing ratings can cause uneven wear and handling problems. If you must replace only two tires, match them to the load rating of your existing tires.