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### Tire Pressure vs Load Calculator and Equation

Determining Operating Tire Pressure vs Load Calculator and Equation

Listed inside the driver's side door area of your vehicle there will be the originally installed tire size, load rating, and tire pressure for the front and rear tires. The size and pressure have been engineered specifically by the manufacturer for correct load capacity and will typically render the best results for tire wear and ride quality. Tire load capacity is directly related to air pressure in the tires. As tire pressure goes up or down, so does the load capacity of the tire. Too much air can wear the tires unevenly in the center and can create a wondering effect on the vehicle's handling. Too little air can wear the tires unevenly on the outer edges and will reduce the tires load capacity below the engineered level.

Figure1, Checking Tire Pressure with Pressure Gage

Definitions:

• Maximum Tire Pressure (Max PSI): This is the tire's maximum safe inflation level. It's usually printed on the tire's sidewall. Over-inflating beyond this point can be dangerous.
• Maximum Tire Load: This refers to the heaviest load the tire can safely carry when properly inflated. Exceeding this load can put undue stress on the tire, leading to premature wear or failure.

If the rated tire pressure is unknown or a more precise tire pressure vs load is required the following equations and procedure can be followed.

1) Equation: Tire Weight / Tire Pressure = Load Capacity Pounds per PSI .

Load capacity per psi calculation

Maximum Tire Load, 3,330 lbs
Maximum Tire Pressure, 95 psi

3329.146 lbs / 95 psi = 35 lbs / psi

Example calculation for trailer with four tires.

(Trailer weight + Load - tongue weight) / 4 is the estimated load on one tire:

Estimated actual load on tire 2,650 lbs divided by 35 lbs/psi = 75 psi per tire

Do not exceed tire load capacity or rated pressure - ever..

Source

Engineers Edge, Kelly Bramble ASME Senior GDTP, F.A.A. Airframe& Powerplant Lic.

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