Pickup Truck Tire Sizes Explained: LT, Flotation, and Load Ratings
Choosing a tire size for truck use starts with the vehicle's approved light-truck or passenger fitment, not with whatever is currently mounted. Pickup and SUV owners comparing truck tire size options often see LT-metric and flotation tire sizing, formats that describe different dimensions. Load range, load index, cold tire pressure, wheel diameter, and the tire placard determine whether a size can carry passengers, cargo, and hauling without exceeding vehicle or wheel limits.
Find the Tire Size Specified for Your Pickup or SUV
The approved tire size for truck and SUV applications is printed on the vehicle tire placard, usually on the driver door jamb, and restated in the owner's manual tire information. That placard lists the size designation the manufacturer selected for the vehicle as built, along with the recommended cold tire pressure for those tires. Size and inflation are separate specifications: the size describes the tire that should be mounted, while cold inflation pressure is the starting pressure used when the tires are cold, not a maximum taken from the sidewall.
Tires already on the vehicle do not establish approved size or load requirements. A previous owner may have installed a different LT tire designation, a flotation size, or a passenger tire that no longer matches the placard. Trim, towing packages, wheel options, and equipment can also change the specified fitment between otherwise similar pickups and SUVs, so the placard for that exact vehicle is the reference. When the door sticker is missing or unreadable, the owner's manual and a dealer or qualified tire professional can confirm the original specification.
Read an LT-Metric Tire Size
An LT-metric marking such as LT265/70R17 is only a decoding example and does not imply compatibility with any pickup or SUV. The LT prefix identifies a light-truck tire designation, built and marked for light-truck service rather than a P-metric passenger tire. The number 265 is the nominal section width in millimeters. The following 70 is the aspect ratio: sidewall height expressed as a percentage of that section width. Together those two figures describe the intended profile, not a guaranteed overall height on every wheel.
R indicates radial construction, and 17 is the wheel diameter in inches that the tire is designed to fit. Neither the R nor the 17 states overall tire diameter; overall height is a result of section width, aspect ratio, rim width, and the actual molded tire. The size string also does not establish load capacity or approved fitment. Load range, load index, speed rating, and the vehicle tire placard sit outside that LT265/70R17 sequence, so reading the size correctly is only the first step in matching a truck tire size.
Decode a Flotation Tire Size
Flotation tire sizing uses a different order of numbers. A marking such as 35x12.50R17LT is only an illustrative flotation size, not a recommendation for any vehicle. The leading 35 is the nominal overall diameter in inches, and 12.50 is the nominal section width in inches rather than millimeters. That width-in-inches format is why flotation sizes look larger on a shelf than an LT-metric size with a similar millimeter width. The rest of the string still has to be read in sequence.
R again identifies radial construction, 17 is the wheel diameter in inches, and the LT suffix is the same light-truck designation used on LT-metric tires. Nominal flotation numbers are catalog values, not measured clearance. Actual overall diameter and section width depend on the specific tire, inflation, load, and the measuring wheel used by the manufacturer. Two tires both marked 35x12.50R17LT can sit at different heights and widths in the fender. Because of that, the stamped size cannot by itself confirm that a flotation tire will clear the body, suspension, or inner liner.
Understand Load Range, Load Index, and Inflation
Load range letters describe a tire's load and inflation category, grouping service conditions rather than naming a brand or tread. Load index is a separate number that represents rated carrying capacity under specified inflation and test conditions. A ply rating printed with the load range does not necessarily state the tire's physical number of plies; modern LT tires often use fewer, stronger belts than the older ply count would suggest. Those markings still matter because tire capacity must support axle loads and intended use without exceeding vehicle ratings or the wheel load rating.
The vehicle's recommended cold tire pressure on the placard is the inflation to use for the specified tires in normal service. Sidewall maximum pressure is a tire limit, not a target, and inflating to that marking does not automatically raise payload. Changing load range, even to a stronger LT tire designation, does not increase the vehicle's payload or towing ratings; those limits stay with the chassis, brakes, and hitch equipment. Any approved alternate fitment needs qualified guidance so load index, inflation, and wheel ratings still cover the axle loads the truck will actually carry.
Confirm Wheel Fit and Clearance Before Changing Size
Before a different truck tire size is mounted, the tire manufacturer's approved wheel-width range, matching wheel diameter, and the wheel load rating plus any pressure limits for that rim still have to be confirmed. A tire can be the right diameter and still be too wide or too narrow for the wheel. Clearance is not a static parking-lot gap. Steering lock, suspension travel, and loaded operation all move the tire relative to the fender, inner liner, and control arms, so a size that looks free at rest can rub when turning or carrying cargo.
A change in rolling circumference also changes how far the vehicle travels per wheel revolution. Speedometer and odometer readings, and on some vehicles stability, driveline, or advanced driver-assistance calibration, can shift with that circumference, subject to the vehicle's own requirements. A size calculator that only matches advertised overall diameter does not approve a fitment. Vehicle guidance and a qualified tire professional are the path for an alternate size, because they can weigh load range, flotation tire sizing versus LT-metric, wheel width, and the systems that depend on the original rolling radius.
Make the Final Size Check for Everyday Use and Hauling
The purchase decision should start from the vehicle-specified size and the service the pickup or SUV will see, not from a catalog diameter that looks similar. Passengers, cargo, and trailer tongue weight still have to stay within the vehicle's stated limits even when the tires are correctly sized. If the truck regularly hauls or tows near those limits, measured axle weights at a scale can show whether the chosen load index and inflation still cover the actual axle loads. That check is about loading the vehicle as it is used, not about rewriting payload ratings.
Many four-wheel-drive and all-wheel-drive pickups and SUVs require matching tire sizes and closely matched rolling circumference on all positions so driveline parts are not forced to absorb a speed difference. Mixing an LT-metric size with a flotation size of similar advertised height can still leave a circumference mismatch. After installation, rubbing, sidewall damage, unexplained pressure loss, or a new vibration is a reason for inspection. Those symptoms cannot be diagnosed from the size marking alone; they can come from mounting, inflation, wheel condition, or a fitment that only looked correct on paper.