LT vs. P-Metric Tires: What the Letters Mean for Your Truck

Two tires can share the same width, profile and wheel size and still be very different. The letters at the start or end of the size tell you which standard the tire was built to, how much weight it can carry, and how much air it needs to carry it. On a pickup or SUV, that matters.

Reading the letters in a tire size

Here is how the common formats look on a sidewall:

• P225/55R17 95T: a P-metric passenger tire, built to the standard of the Tire and Rim Association (TRA), which sets tire standards in North America. 225 is the width in millimeters, 55 is the aspect ratio, R means radial, 17 is the wheel diameter in inches, and 95T is the load index and speed rating.
• 225/55R17 97T: no letter in front means Euro-metric, also called hard metric or ISO metric. It follows the European (ETRTO) standard. It is the same kind of tire, with different load tables.
• LT265/70R17 121/118S Load Range E: an LT-metric light truck tire. The two load index numbers are for single and dual rear wheel use, and the load range letter gives its strength class.
• 35×12.50R17LT: a flotation light truck size, measured in inches. It is roughly 35 inches tall and 12.5 inches wide.
• 225/70R15C: a European commercial, or C-type, tire, made for vans and delivery vehicles that carry heavy loads.
• ST225/75R15: a special trailer tire. ST tires are made for trailers only; you will find them in our trailer tire category.

P-metric vs. Euro-metric: close cousins

Both are passenger tires, and many cars, crossovers and SUVs leave the factory on one or the other. They can often replace each other, but only after you compare load capacity at your placard pressure. The difference is in their load tables:

• Most standard-load (SL) P-metric tires reach their maximum load at 35 psi. Extra Load (XL) P-metric tires usually reach it at 41 psi.
• Standard-load Euro-metric tires reach their maximum at 36 psi. XL or “Reinforced” Euro-metric tires reach it at 42 psi.

The load index alone can mislead you. In published industry tables, a P225/55R17 95T carries up to 1,521 lb at 35 psi, while a 225/55R17 97T carries up to 1,609 lb at 36 psi. Tire makers warn that an equal or higher load index does not always mean equal or higher capacity at every pressure, especially between P-metric and Euro-metric tires. The safe test is simple: at your placard pressure, the replacement must carry at least as much as the original.

The maximum pressure molded on the sidewall, often 44 or 51 psi on a standard-load passenger tire, is the most the tire can safely hold. It is not the pressure to run. Use the placard.

What makes an LT tire different

LT tires are built for harder work. Compared with passenger tires, they usually run at higher pressures, are designed to carry heavier loads, and use heavier-duty construction in the sidewall, shoulder and tread, which usually makes them heavier too. Their strength is shown as a load range. For LT-metric sizes:

• Load Range C: 6-ply rating, typically 50 psi maximum
• Load Range D: 8-ply rating, typically 65 psi
• Load Range E: 10-ply rating, typically 80 psi
• Load Range F: 12-ply rating, typically 95 psi

“Ply rating” is a strength equivalent carried over from older tire construction, not a count of the layers inside. Some flotation sizes also come in Load Range B. The federal UTQG treadwear, traction and temperature grades apply to passenger car tires, so LT tires usually do not show them.

Why LT tires need more air

A tire carries weight with its air pressure. Size for size, an LT tire needs more pressure than a P-metric tire to carry the same load. Mount LT tires on a truck and run them at the old passenger-tire pressure, and they may be underinflated for the weight. Underinflation builds heat, and heat is what damages tires over time.

Here is an example from published load tables. Say a half-ton pickup came with P255/70R17 110S tires set to 35 psi. That tire is rated for 2,337 lb at 35 psi. But when passenger tires are used on a light truck, their capacity must be reduced by dividing by 1.10, so the real figure is about 2,125 lb. An LT265/70R17 Load Range E replacement needs about 45 psi, where it is rated for 2,255 lb, to cover that load. At 35 psi it would fall short.

That is why a good installer checks load and inflation tables whenever you change tire type, tells you the new pressure, and adds a label at the placard showing the new size and pressure. Never run below the pressure the vehicle maker recommends, and never exceed the maximum pressure on the sidewall.

When you need LT tires, and when P-metric is fine

Stay with LT if your placard lists an LT size. Many heavy-duty pickups, such as 3/4-ton and 1-ton models, come with LT tires from the factory. USTMA guidance advises against replacing original LT tires with P-metric or Euro-metric tires unless the vehicle manufacturer says it is OK. These trucks may also list different front and rear pressures; keep that difference.

Heavy towing and hauling. When you tow, the trailer’s tongue weight is carried by your truck, mostly on the rear tires, and a loaded bed adds more. LT construction is designed for that kind of steady, heavy work, which is why many owners who tow or haul regularly choose LT tires in a suitable load range. Keep in mind that new tires never raise your truck’s payload or towing ratings; those come from the vehicle maker. Check the weight ratings on the door-jamb label, follow the towing guidance in your owner’s manual, and check tire pressures before every tow.

P-metric is fine when the placard lists it and your use matches. If you mostly drive on pavement, carry normal loads and tow within the owner’s manual limits, a passenger tire of the right size and load index is what the vehicle was designed around, and it usually rides more smoothly. Highway and touring tires are a common choice here, and you can also browse SUV and crossover tires.

Switching from P-metric to LT on purpose? Some drivers who spend a lot of time on gravel roads or trails choose LT tires for their sturdier build, and many all-terrain tires come in LT sizes. Go in knowing the trade-offs: a firmer ride, higher pressures, usually more weight, and possible changes in handling. Confirm with the vehicle maker or a tire professional that your wheels are rated for the higher pressure and that the tires clear the body and chassis, and have the installer set pressures from the load tables.

Never mix types. Do not combine passenger tires and LT tires on the same vehicle.

P-metric, Euro-metric and LT side by side

A quick checklist before you order

1. Read the placard on the driver’s door jamb or check the owner’s manual. Note the tire size, type (P, Euro-metric or LT), load index or load range, and cold pressures front and rear.
2. Ask whether your use has changed: more towing, more payload, more dirt roads.
3. Keep the same type unless you have a clear reason and a tire professional’s OK to switch.
4. Make sure the new tires can carry at least the original load, at the placard pressure or at the pressure the load tables call for if you change type. Match or beat the speed rating to keep the vehicle’s speed capability.
5. Buy four matching tires.

Then shop by size in our light truck or passenger car tire categories. Orders ship free to the contiguous U.S. (the 48 states plus Washington, DC) by UPS or FedEx, and tracking is emailed when your order ships. You can also send tires straight to a local installer: call the shop first, then enter its address as the shipping address and the shop’s name in the Company name field. Our shipping policy page has the details.