What You’ve Always Wondered About Truck Tires

Thinking about upgrading from your factory P-metric truck tires to 35-inch LT All Terrain tires with an uprated load range and E-ply rating?

Have no idea what we’re talking about but want to learn? Well then, friend, you’re in the right place.

You might have thought you previously decoded tire sizes, but the world of truck tires presents a slew of new terminology, options, and guidelines.

To help you sort through it all, here are answers to some of the most common questions about truck tire sizes.

Can I replace P truck tires with LT truck tires?

Yes, Original Equipment (OE) P (P-metric tires) can be replaced with LT (light truck) tires, but the opposite swap should not occur. If your truck was fitted with LT tires as OE, then a “downgrade” in tire rating and capability is not advisable. Your truck was engineered from the ground up with tire specification in mind, and its various load capacities and limitations are, in part, based on tires.

But backing up for just a moment, definitions to make sure you’re properly informed on these different tire specifications:

P/P-metric tires: P stands for “Passenger” tires. These tires are designed for use on passenger vehicles such as light-duty pickup trucks (quarter-ton or half-ton capacity), cars, minivans, and SUVs.

P-metric tire sizes are sometimes denoted by a “P” at the front of the tire size, e.g., P275/65R18.

LT: LT stands for “Light Truck.” LT tires are intended for use on vehicles designed for heavier hauling and towing duties. This includes medium-duty and heavy-duty pickup trucks with three-quarter-ton to 1-ton capacity, as well as select SUVs and full-size vans. LT tires achieve higher load ranges and ply ratings as compared to P-metric truck tires. See What’s a tire ply rating? for more details.

The LT specification can be found as a prefix or suffix to the tire size information.

So, why would a truck be fitted with P-metric tires from the factory in the first place? Or asked another way: Some trucks are equipped with the same tire specification found on minivans?

P tires prioritize standard on-road performance, comfort, and wear. Not all trucks are destined from the factory for hauling and towing heavy loads, backcountry adventures (even if a 4x4), or other heavier duty types of activities. P tires are suited to trucks with light duty driving in mind, or that are more oriented toward luxury. P-metric tires generally deliver less rolling resistance as well, and therefore superior fuel economy.

A jump from P truck tires LT truck tires could be motivated by any number of factors, apart from sharing tire DNA with minivans, that is…oh, the indignity.

• You want an extra tire performance and capacity buffer for hauling and/or towing. (Note: Upgrading your tires’ specification doesn’t mean your truck is up to the task of exceeding its payload or towing capacity.)
• You regularly approach the load capacity of your truck with heavy payloads and/or towing, sense your OE tires seem stressed, and are looking for increased tire strength and support.
• You’ll be taking your truck off-road and desire a boost in durability and performance, and many All Terrain and Mud Terrain tires are LT spec.
• You prefer the heavy-duty look of most LT truck tires as compared to P truck tires. (We feel you.)

What should one expect when replacing P truck tires with LT truck tires?

Aside from the potential performance improvements noted just above, a set of LT truck tires might influence your everyday on-road driving too. The uprated load range and ply rating, which are accomplished via a stiffer and more durable sidewall construction, might also result in a harsher ride.

If you’re running P-metric All Season tires on your truck, and your new set of LT truck tires are All Terrains or Mud Terrains, then a change in road noise and handling and performance characteristics might also be perceptible. See All Season Tires vs. All Terrain Tires for more info.

What does XL mean on a truck tire?

XL stands for “Extra Load.”

The XL designation is indicated at the end of a tire size expression, e.g., 255/60R18 XL.

As compared to SL (Standard Load) tires of the same size, XL tires are stronger and can support higher vehicle weight/load. If a truck is fitted with P-metric tires as OE, they’re commonly XL spec.

Similar to the OE P-metric tires vs. LT truck tires choice, it’s acceptable to “upgrade” from OE SL tires to XL tires, but not the other way around. If your truck has XL tires from the factory, then that heavier duty specification needs to be maintained.

Note that some tires offer both SL and XL specification in the same tire size. For example, 235/65R17 (SL specification) and 235/65R17 XL (XL specification). If your vehicle is equipped with XL tires from the factory, be sure to select the XL specification when it’s tire replacement time.

Are truck tire sizes expressed differently than car tires sizes?

Most truck tire sizes are indistinguishable from car, SUV, or CUV tire sizes. The basic format is equivalent: Section width (in millimeters) “225,” aspect ratio of sidewall “45,” then tire and wheel diameter “17.”

225/45R17

However, flotation tires, which are commonly fitted to trucks, are expressed differently.

33X12.50R18

Unlike standard tire sizes that are expressed in metric format, flotation tires are expressed exclusively in inches. In the example immediately above, 33 = 33-inches in diameter, 12.50 = 12.50-inches wide, and 18 = 18-inch wheel diameter fitment.

What’s the difference between ST and LT truck tires?

LT truck tires are appropriate for towing ST (Special Trailer) tires, but that’s the only acceptable arrangement. ST tires are specifically engineered for fitment to various types of trailers.

Both types of tires can be engineered to manage heavy loads, but that’s about where the similarities end. ST tires are not suitable for use on trucks or any other motor vehicles.

Need some help determining which direction to go for your truck tires? Give us a call at 866-961-8668.