Sidewall maximum versus recommended pressure

Two numbers live on every car, and they answer different questions. The placard answers “what cold pressure does this vehicle want?” The sidewall answers “what is the maximum cold inflation this tyre is built for at its maximum load?”

A typical 205/55R16 all-season might show 3.4 bar or 51 psi on the flank. The Golf or Civic it is bolted to might want 2.3 or 2.5 bar. Inflating to the sidewall maximum because it “looks official” overloads the centre rib.

Plus-sizing does not move you onto the sidewall number. You still start from the vehicle placard, then check the tyre maker’s load/inflation table so the new tyre can carry the same axle load.

Vans on C-type tyres are the exception that confuses people: their placard already lives in a higher band. That is still a vehicle number, not a licence to hit the tyre’s printed maximum for fun.

If you only remember one rule: recommended is the door; maximum is the rubber.