After you have changed the tires or simply adjusted the tire pressure, you have to inform the smart that it should adopt the new pressures. This is relatively easy for vehicles with Passion line or higher: You can use the arrow keys on the steering wheel to go through the settings on the on-board computer. There you can "Take over the current pressures" and it is already successfully completed.
For vehicles with a monochrome display, it is a bit more complex: For the smart to take over the new tire pressure, you first have to completely empty the tire, down to 0 bar. Then bring the tire pressure to just over 3 bar and wait 5 minutes. Then you can set the desired pressure on the tires and this will then be saved.
Tire pressures recommended by the manufacturer for the smart fortwo and convertible:
2.3 bars at the front
2.5 bars at the rear
Tire pressures recommended by the manufacturer for the smart forfour:
2.2 bars at the front
2.5 bars at the rear