Tyre pressures must be checked at least monthly and always before going on a long journey, you'll find the right tyre pressures for your car in the handbook. If you can't, or have lost the handbook, ask your local tyre dealer to look them up for you. Once you know the correct pressures you should write them down somewhere easy to find, a good place is inside the fuel filler flap or under the bonnet .
If you're checking the pressures yourself, try to use a digital tyre pressure gauge - they're not expensive but they are more accurate than the gauge on most garage forecourts. It's important to check the pressures when your tyres are cold, so wait for about an hour from when you last drove on them.
Another thing to remember is that if you're driving at constant high speeds or are carrying a heavy load, the pressures can be different - again, consult your car's handbook or ask your Tyre dealer for advice.
Under or over-inflated tyres can seriously affect your car's handling, ride and braking behaviour and could lead to an accident. In other words, it pays to get the pressures right.
Most Blowouts are caused by under-inflated tyres, when a tyre is under-inflated it becomes very hot and the sidewalls start to melt, the sidewall then fails and that is what most people call a blowout!
It's worth noting that you can't tell just by looking, so always use a gauge. Also remember that a wrongly inflated tyre will wear out quicker, which may cost you more than just money!