LT vs P-Metric Tires: Load Range C, D and E Explained

Two tires, one size, different jobs

Search for tires for a pickup and you'll often see the same size twice: P265/70R17 and LT265/70R17. Same numbers, different letters in front. That letter matters more than most people expect.

NHTSA's tire safety material lists what the leading letters mean: P for passenger car and LT for light truck. Michelin adds that a P means the tire's loads follow U.S. Tire and Rim Association standards for passenger tires.

• P-metric tires go on cars, minivans, crossovers, many SUVs and plenty of half-ton pickups.
• LT tires are built for heavier service: towing, hauling, heavy-duty pickups, vans and many off-road builds.

The two are different service types. Treat any change from one to the other as a fitment question, not a style choice.

Load range and ply rating

LT tires carry a load range letter, usually shown on the sidewall and in the spec table as "Load Range E" or just "LRE".

Bridgestone's definition: load range replaces the former ply rating term and identifies a tire's load and inflation limits. So when you hear "10-ply tires," that's the old language for what's now marked as load range E. The number is a rating, not a count of the layers inside the tire.

The letters you'll see most on light trucks:

A higher letter means the tire is built to carry more weight, at a higher maximum inflation pressure. The exact maximum load and pressure for any tire are molded on its sidewall near the bead, so read them there rather than from a chart.

Two load numbers on one tire

LT tires usually show a load index like 121/118. Cooper explains that the first number is the load capacity for a tire in a single application and the second is for dual application, such as pairs on a dually's rear axle. On a regular pickup, compare the first number.

Check it against your current tire here:

Why P-metric tires get "de-rated" on trucks

There's a rule that surprises a lot of truck owners. Under the federal tire selection standard, FMVSS No. 110, when a vehicle maker puts passenger tires on a multipurpose passenger vehicle, truck, bus or trailer, each tire's load rating is divided by 1.10 before it's checked against the axle's weight rating.

In other words, a P-metric tire on a pickup or SUV is counted as carrying less than its full passenger-car rating. Toyo's technical bulletin on light trucks explains why: P-metric tires are designed mainly for passenger cars and may see more severe service on light trucks.

You don't need to do this math yourself. The vehicle maker already did it when it chose the tire size and pressure on your door placard. It's the reason you shouldn't drop to a lower load index, or move from LT to P-metric, on your own.

Why pressures change when you switch

Toyo's bulletin makes a second point that catches people out: size for size, an LT tire needs more air pressure to carry the same load as a P-metric tire. It warns that failing to adjust pressure to meet the vehicle's load requirement leads to tire fatigue and eventual failure from excessive heat build-up.

So if you move a half-ton truck from P-metric to LT tires, the placard pressure may no longer be the right number for the new tires. The fix is to look up the pressure that gives at least the original load capacity in the tire maker's load and inflation table, which is exactly what Toyo's guidelines for using those tables cover.

That's a job for the installer with the tables in hand, not a guess at the air pump.

When does a truck need LT tires?

Use this order:

1. The placard says LT. If your vehicle maker fitted LT tires, the replacements should be LT with at least the same load range and load index. Toyo's rule for any light truck: a replacement must offer equal or higher load carrying capacity than the original equipment tire.
2. You tow or haul near the vehicle's limits. Heavy trailers, slide-in campers, work trucks loaded with tools and material. Check your owner's manual for any tire guidance it gives for towing.
3. You're switching tread type. Many all-terrain and mud-terrain tires come mainly in LT sizes. Our guide to all-terrain vs highway tires covers that choice.

And when a truck probably doesn't need LT tires: a half-ton pickup or SUV that came on P-metric tires and is used as a daily driver, with occasional light towing within the owner's manual limits. Moving to LT there isn't wrong, but it changes pressures, and you may notice the ride.

P-metric, LT, XL: how they relate

P-metric tires come in two load versions, standard load and extra load (XL). LT tires use load range letters instead. Our guide to XL vs SL tires covers the passenger side of that.

Those example markings show the format, not a recommendation for any vehicle.

Before you order

• Read the placard. It lists the size, including whether it starts with P or LT, and the cold pressure. Our guide on how to read tire size walks through every piece.
• Match or beat the load. Compare load index and speed rating with the load and speed rating check.
• Plan the pressure. If you're changing type, have the installer set pressures from the tire maker's load and inflation tables.

The Tire Size Finder reads the size off your door-jamb sticker. Then shop tires by size. Extreme Tires installs at the Sunrise shop or by mobile van in Miami-Dade, Broward and Palm Beach counties; elsewhere in the 48 states and DC, the order ships to your address. See how installation works, or call (954) 773-1896.