Don't forget, if you're going abroad you need to put in kg/sq cm. Metric air can be found anywhere abroad but is difficult to find in the UK. And remember to change it back to Imperial air as you come home.
There's a strict limit on the amount of metric air you're allowed to import so deflate your tyres before you board the ferry and re inflate using an Imperial foot pump when you get onto British soil.
Not a lot of people know this.