RV & Trailer Tire Pressure Calculator (From Scaled Axle Weight & Load Range)

How it works

load per tyre = axle weight ÷ tyres × (1 + side imbalance) · dual rating ≈ 0.91 × single · load-inflation approximation: load ≈ max load × (psi ÷ max psi)^0.8 → required psi = max psi × (load ÷ max load)^1.25 · trailers: run sidewall max; motorhomes: table pressure + 5 psi

The pressure on a tyre's sidewall is the pressure at which it carries its maximum load, not a recommendation for every load — motorhome and truck tyres are properly inflated from the manufacturer's load-inflation table using the weight each axle actually carries, plus a small cushion. Trailers are the exception: ST and LT trailer tyres are run at their maximum because sway resistance, heat and the trailer's hard ride matter more than comfort, and the table is used only to check that the load is within the rating with a healthy reserve. Everything starts with a scale ticket; a guess from the brochure weight is how tyres get overloaded.

Worked example

A fifth-wheel axle scaling 6,200 lb on two ST235/80R16 load-range E tyres (3,520 lb at 80 psi): with a 10% side allowance each tyre carries about 3,410 lb — 97% of its rating with only 3% reserve, so LR G tyres (4,400 lb at 110 psi, if the wheels allow) would be wise. The axle is at 89% of its 7,000 lb GAWR. As a trailer, the tyres run at 80 psi cold regardless.

Frequently asked questions