Plus-size wheels and estimated PSI

Plus-sizing means a larger wheel and a shorter sidewall with a similar overall diameter. The tyre still has to carry the same axle load. A shorter sidewall does not want less air.

Model charts on this site list estimated cold pressures for sizes often seen on that body class. They start from the catalogue midpoint and add a small delta. They are labelled estimates.

If the new tyre’s load index is lower than original equipment, stop. No pressure will legally make up a missing load index on a passenger car.

Staggered plus-size (wider rear) can list different front and rear targets from the factory. Keep that split. Do not average them.

Never lower pressure to “make 20s ride like 16s.” Buy a more comfortable construction, or go back a wheel size.