Replacement Load Equivalence Tool
Find the pressure a replacement tire needs to carry the same load as the original at its placard pressure. SL, XL and LT supported.
Compare capacity at specified pressures.
Replacement Load Equivalence Tool: Tire Size Inputs
Compare two tire sizes here. Use the formulas and reference tables below for this tool's specific calculation.
How Replacement Load Equivalence Tool Works?
The Replacement Load Equivalence Tool works by calculating the original tire's capacity at the placard pressure and solving for the pressure that gives the replacement tire the same capacity. The tool uses 4 steps.
Enter the original tire
Type the original index and construction, for example 91 SL at a placard pressure of 33 psi (2.3 bar).
Compute the target load
The tool returns 579 kg (1,276 lb) at 33 psi.
Enter the replacement
Type the replacement, for example 94 XL.
Read the pressure
The tool solves for the pressure at which the 94 XL tire carries 579 kg and returns about 34.1 psi (2.35 bar).
Replacement Load Equivalence Tool Formula
The Replacement Load Equivalence Tool formula is p_rep = p_ref,rep × (L_target ÷ L_max,rep)^(1 ÷ 0.7).
L_target = L_max,orig × (p_placard ÷ p_ref,orig)^0.7p_rep = p_ref,rep × (L_target ÷ L_max,rep)^(1/0.7)p_rep ≤ p_ref,rep- L_target
- Load the original carries at placard pressure
- p_ref
- Reference pressure of each construction
- p_rep
- Required replacement pressure
Worked example
An original 91 SL at 33 psi carries about 579 kg (1,276 lb). A replacement 89 SL tire (580 kg max at 36 psi) needs 35.9 psi (2.47 bar) to match, and a replacement 93 XL tire needs about 35.6 psi (2.45 bar).
Replacement Load Equivalence Tool Conversion Table
The Replacement Load Equivalence Tool conversion table shows the pressure 4 replacement tires need to carry the same load as a 91 SL tire at 33 psi.
| Tire | Max capacity | Reference pressure | Required pressure |
|---|---|---|---|
| Original 91 SL at 33 psi | 615 kg | 36 psi | 33.0 psi (2.28 bar) |
| Replacement 94 XL | 670 kg | 42 psi | 34.1 psi (2.35 bar) |
| Replacement 91 XL | 615 kg | 42 psi | 38.5 psi (2.65 bar) |
| Replacement 89 SL | 580 kg | 36 psi | 35.9 psi (2.47 bar) |
| Replacement 93 XL | 650 kg | 42 psi | 35.6 psi (2.45 bar) |
Values use the 0.7-power approximation. Tire maker load-inflation tables govern final settings.
What is Replacement Load Equivalence Tool?
A Replacement Load Equivalence Tool is a tool that finds the inflation pressure a replacement tire needs to carry the same load as the original tire at the placard pressure. An XL replacement often needs a different pressure from the placard value.
The tool answers the common question after a plus-size change: which pressure keeps load capacity equal to stock.
A replacement that needs more than its maximum pressure to match cannot carry the original load. The tool marks those tires as unable to match.
What are the uses of Replacement Load Equivalence Tool?
There are 4 main uses of the Replacement Load Equivalence Tool, including plus-size pressure setting and XL conversions.
Plus-size pressure setting
Set pressure on lower-profile replacement tires.
XL conversions
Find the XL pressure that matches SL capacity.
LT conversions
Set LT tire pressure on a vehicle placarded for P-metric tires.
Tire shop guidance
Give customers a documented pressure after a size change.
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