P (passenger car tire)

How to read it

In P215/65R15, the P indicates a tire for passenger cars and other light vehicles (NHTSA). Ford’s owner’s manual describes it as a tire designated by the Tire and Rim Association that may be used on cars, SUVs, minivans and light trucks, and Yokohama calls tires designed to that association’s standard P-metric sizes. The federal standard for these tires defines a passenger car tire as one intended for passenger cars, multipurpose passenger vehicles and trucks with a gross vehicle weight rating of 4,536 kg (10,000 lb) or less (FMVSS 139). The rest of the size reads as any other: Section width (215 in 215/65R15), Aspect ratio (65 in 215/65R15), construction and Rim diameter (15 in 215/65R15).

Also searched as: P in tire size, P-metric.

P-metric and Euro-metric

The look-alike is the same size without the P, such as 215/65R15: a Euro-metric size, designed to the European Tyre and Rim Technical Organization’s standard. Yokohama says the two are dimensionally equivalent but typically differ subtly in load-carrying capability. Bridgestone’s replacement tire manual gives an example: at 220 kPa (32 psi), a P205/65R15 and a 205/65R15, both standard load and both load index 92, carry 1,334 lb and 1,257 lb. Bridgestone says the Euro-metric tire carries less at every pressure in its table, even with the same load index.

Standard load, extra load and light load

Yokohama says passenger tires, P-metric and Euro-metric alike, are marked light load (LL), standard load (SL) or extra load (XL). Bridgestone’s manual gives the pressure at which a P-metric tire reaches its maximum load: 240 kPa (35 psi) for standard load and 280 kPa (41 psi) for extra load. It says light load versions, found among P-metric sizes of 45 series and lower and T-type spares, run at the same pressures as standard load but carry less.

On an SUV, pickup or van

When passenger car tires are fitted to a multipurpose passenger vehicle, truck, bus or trailer, FMVSS 110 divides each tire’s load rating by 1.10 before comparing the tires on an axle with that axle’s rating. Bridgestone’s manual works the example of a P235/70R15 at 35 psi: 860 kg (1,896 lb) on a passenger car, 782 kg (1,724 lb) on a light truck. The rule reduces passenger car tires only; an LT tire counts at its full rating.