Tyres are crucial to the driving experience, but they are also very confusing. Labels, sizes, technology - a lot has changed over decades of car use. Tyre sizes relate to the width and height of the tyre you fit to your car, as well as the maximum speed you are allowed to travel with those tyres.
Why do I need to know the tyre size?
If you have just bought your car and are thinking of taking it to a dealer or tyre specialist for new tyres, you probably don't need to worry about the specifications of your tyres. If you need them in an emergency, such as a puncture, you can find them (along with the recommended pressure) on your vehicle's specification plate.
Which tyre sizes fit your vehicle?
On the fuel filler cap, on the pillar inside the door panel or sometimes in the glove box, you should find a diagram showing the different tyre pressures for fully loaded and continuous high speed - this will give you the tyre size range for your vehicle.
This is also in the handbook, but specifications may vary and used vehicles may have aftermarket wheels fitted.
If you are unsure of your tyre pressure on aftermarket wheels and tyres, as a rule of thumb about 30 to 35 psi is a safe range. Make sure the pressure is equal on both sides of the vehicle, but some vehicles use different pressures for front and rear. If in doubt, consult your manufacturer or tyre specialist.
