Load range letters, load index and the difference between a passenger and a light truck tire. The specs that matter for a work vehicle.
The sidewall of a tire carries several numbers that determine whether it is right for your vehicle and your loads. Most buyers look at the size and the tread pattern and never read the rest.
Load index
A numeric code that corresponds to the maximum load a single tire can carry at its rated pressure. Higher number, higher capacity. Your vehicle placard specifies a minimum, and going below it is not a shortcut worth taking.
Load range
Letter designations — C, D, E and so on — that indicate the tire construction and the pressure at which it achieves its rated load. Higher letters generally mean stronger construction and higher maximum inflation pressure.
These correspond to the older ply rating terminology, which described actual layers of material. Modern tires use fewer, stronger plies, so the ply rating is now a strength equivalence rather than a literal count.
P-metric versus LT
A tire size beginning with P is a passenger tire. One beginning with LT is a light truck tire, built with stronger construction for heavier loads.
This matters because the same nominal size exists in both, and they are not interchangeable for a truck that carries or tows. Passenger tires on a truck used as a truck are a common and consequential mistake.
The pressure detail people get wrong
The pressure stamped on the sidewall is the maximum, not the recommendation. The correct pressure is on the vehicle door placard, and it is the number the vehicle was engineered around.
Running an E-rated tire at its maximum sidewall pressure on an empty half-ton produces a harsh ride, a small contact patch and center tread wear. Running it too low under load generates heat and risks failure.
For trucks that run loaded some days and empty others, adjusting pressure to the load is legitimate and worth learning. Load and inflation tables exist for exactly this.
Speed rating
A letter indicating the maximum speed the tire is designed to sustain. Generally, do not go below what the vehicle came with — it also correlates with construction and heat handling, not just top speed.
What actually matters for a work truck
- Load index at or above the vehicle placard requirement
- LT construction if the truck carries or tows regularly
- Load range suited to your heaviest realistic load
- Pressure set to the load, checked cold
- Matching across an axle, because mismatched capacity is a problem
Where we fit
Elite Tire & Brake matches tires to how your vehicle is actually used, in our Lubbock shop or at your location. Call (806) 458-2709.
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Mobile tire and brake service across Lubbock, Wolfforth, Shallowater, Slaton, Idalou and the surrounding South Plains — plus a full-service shop at 13209 Frankford Ave, Suite 29.