LT vs P-metric tires on half-ton trucks: pressure, payload, and ride math
LT versus P-metric truck tire construction: load derating, inflation tables, placard math, towing margin, and the ride each one buys you.
Edited by Nicole
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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 on the tire before you compare price or tread.
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.
The door placard settles the baseline. 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? An owner who tows near the limit, hauls a camper, or runs rocky roads where a soft sidewall means a plugged weekend. The tradeoffs depend on use: an LT tire 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.
The Falken Wildpeak A/T4W spans both constructions in half-ton sizes, so confirm the load index and price per variant on that page, not the tread photo. The same split runs across the Toyo Open Country A/T III line, where the P, XL, and LT versions of one tire size carry different indexes and pressures. Shop the rest of the category in the wheel-tire clearance department.
Four checks close the decision: confirm the placard load per tire, confirm the construction letter, pull the inflation-table pressure, and verify the wheel is rated for it. Not every factory wheel is 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.
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