Tire Pressure Specification Comparator
Compare door placard pressure, sidewall maximum and tire maker guidance side by side in psi, bar and kPa. See which value to use.
Compare placard and manufacturer guidance.
Tire Pressure Specification Comparator: Tire Size Inputs
Compare two tire sizes here. Use the formulas and reference tables below for this tool's specific calculation.
How Tire Pressure Specification Comparator Works?
The Tire Pressure Specification Comparator works by listing every pressure value that applies to one tire and vehicle and showing what each value means. The tool uses 4 steps.
Enter the placard values
Type the front and rear cold pressures from the door placard, normal and full load.
Enter the sidewall maximum
Type the maximum pressure molded on the sidewall.
Enter tire maker guidance
Type any pressure from a plus-size or load equivalence table.
Compare
The comparator converts all values to psi, bar and kPa and marks the operating value and the limits.
Tire Pressure Specification Comparator Formula
The Tire Pressure Specification Comparator rule is P_placard ≤ P_operating ≤ P_sidewall-max, with all values measured cold.
P_placard ≤ P_set ≤ P_maxP_warn ≈ 0.75 × P_placard1 psi = 0.0689476 bar = 6.89476 kPa- P_placard
- Vehicle maker's cold pressure
- P_max
- Sidewall maximum pressure
- P_warn
- Tire pressure monitoring system (TPMS) warning point
Worked example
A placard lists 33 psi (2.3 bar), and the sidewall lists 51 psi (3.5 bar) maximum. The operating pressure is 33 psi cold. The sidewall value is a limit, not a target.
Tire Pressure Specification Comparator Conversion Table
The Tire Pressure Specification Comparator conversion table lists 6 pressure values for a sample car in 3 units.
| Value | psi | bar | kPa |
|---|---|---|---|
| Door placard (front / rear) | 33 / 33 psi | 2.3 / 2.3 bar | 228 / 228 kPa |
| Placard, full load | 36 / 38 psi | 2.5 / 2.6 bar | 248 / 262 kPa |
| Sidewall maximum (SL) | 44 psi | 3.0 bar | 300 kPa |
| Sidewall maximum (XL) | 51 psi | 3.5 bar | 350 kPa |
| Tire maker plus-size advice | 35 / 35 psi | 2.4 / 2.4 bar | 241 / 241 kPa |
| TPMS warning threshold (−25%) | 25 psi | 1.7 bar | 171 kPa |
Values are a sample. Each vehicle's placard and each tire's sidewall give the real values.
What is Tire Pressure Specification Comparator?
A Tire Pressure Specification Comparator is a tool that separates the different pressure numbers a driver sees and shows which number to inflate to. The placard pressure is the operating target. The sidewall pressure is a limit.
The placard pressure applies to the original tire size and load index. A size or load change can call for a different pressure from a load equivalence table.
All values are cold pressures, measured before driving or after 3 hours parked.
What are the uses of Tire Pressure Specification Comparator?
There are 4 main uses of the Tire Pressure Specification Comparator, including pressure setting and plus-size pressure checks.
Pressure setting
Pick the right number for a gas station inflation.
Plus-size checks
Compare placard pressure with tire maker advice after a size change.
TPMS resets
Know the pressure that triggers a TPMS warning.
Load changes
Switch to full-load pressures for a loaded trip.
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