LT vs P-metric tires on half-ton trucks: pressure, payload, and ride math

One sidewall size can hide two different tires. A 275/65R18 exists as P-metric and as LT, and they do not carry weight the same way. Check the construction letter before comparing anything else.

The math is the trap. On a truck, a P-metric tire loses about ten percent of its sidewall load rating; divide by 1.1 before trusting the number. An LT keeps its full rating but needs far more air to earn it. Expect 65 to 80 PSI on a load range E, not the 35 on the door sticker.

Start with the door placard. It lists the size, construction, and cold pressure the payload rating depends on. Switching to LT means looking up the pressure that matches the placard load in the tire maker's load-inflation table. Do not guess. Too little air overheats an LT under load; too much beats up the cab.

Who needs LT? Owners who tow near the limit, haul a camper, or run rocky roads where a soft sidewall means a plugged weekend. The tradeoffs depend on use: an LT can add ten pounds per corner, firm up the empty ride, and cost fuel. A commuter who tows twice a year should verify whether an XL P-metric covers the load first.

Compare the Falken Wildpeak A/T4W product page for a family that spans both constructions in half-ton sizes; check the load index per variant, not the tread photo. The same check works on the Toyo Open Country A/T III page, where P, XL, and LT versions of one size carry different indexes and pressures. Shop the rest of the category from the wheel and tire clearance department.

Before checkout: confirm the placard load per tire, confirm the construction, pull the inflation-table pressure, and verify the wheel is rated for it. Some factory wheels are not rated for 80 PSI. Then price the set of four with the four-tire price math guide and recheck capacity against the load range guide.