Switching to larger tires or heavy-duty LT-rated tires? Use our interactive truck tire calculator to compute speedometer error, height differences, clearance rubbing risks, and recommended safety inflation pressures.
Upgrading your truck's tires is one of the most practical modifications you can make, but choosing the wrong fitment or incorrect inflation pressure is a common headache.
Before mounting your new tires, check their diameter differences, speedometer offsets, and safety load adjustments.
Safety First: If you are switching from passenger (P-metric) tires to light truck (LT) tires, do not run them at the factory door sticker pressure under heavy loads. LT tires require higher pressures to carry equivalent weight safely.
Interactive Tool
Interactive Truck Tire Size & Load Calculator
Compare tire sizes to calculate speedometer error, height differences, and look up recommended tire pressure adjustments when switching from passenger (P-metric) to light truck (LT) tires.
Stock Height31.6"
New Height32.7"
Height Difference+3.5% (+1.1")
Speedometer Impact
Speedometer Reads Slow
When your speedometer reads 60 MPH, your truck's actual speed is 62.1 MPH.
Fitment & Rubbing Warning
This tire is over 1 inch taller than stock. Check clearance at full steering lock. You may experience rubbing on the crash bars, upper control arm (UCA), or bumper valance. A leveling kit or wheel spacer adjustment may be required.
P-Metric to LT Pressure Lookup
Passenger (P) tires carry load at lower pressures than heavy-duty Light Truck (LT) tires. If you switch from factory P-metric tires to LT tires, inflating them to the door sticker pressure (usually 35 PSI) will underinflate the tires, causing uneven wear, heat, and lower load capacity.
PSI
Recommended Inflation
Recommended LT Cold Pressure
45PSI
LT tires need higher cold inflation pressure to maintain the load capacity of the factory P-metric tires. For everyday driving, add **10 to 15 PSI** over your door sticker pressure (typically 45–50 PSI).
Note: Verify load index charts for your specific tire model. Never exceed the max PSI listed on the tire sidewall (typically 50, 65, or 80 PSI depending on load range C, D, or E).
Why Calibration and Load Capacity Matter
Universal calculators often ignore the differences between P-metric and LT tires. In addition, going more than 1 inch larger than stock can cause rubbing on your truck's crash bars, bumper valance, or control arms at full steering lock.
If you need a detailed breakdown of tire load ratings, tread styles, and towing limits, read our full Pickup Truck Tire Basics Buying Guide.