Forecourt compressors versus a proper gauge

A supermarket or petrol-station compressor is a pump, not a laboratory. The built-in meter can be 0.2 bar off, the hose leaks, and the bay is on a slope.

Use the machine to get close, then check with a pocket gauge once you are back on level ground and the tyre has sat for a minute.

Digital units you keep in the glovebox should be replaced every few years or checked against a known good gauge at a tyre shop.

Some newer cars show live psi on the dash. Those readings are often warm. They are a useful cross-check, not a licence to skip the cold morning.

If the compressor will not shut off at your target, you are not obliged to wait until it bursts the bead. Stop, measure, walk away.