Maybe you are bored with your steel wheels or your existing alloys are looking a little tired. New wheels can make or break a car – but before you choose a style you need to know what will and won’t fit your car. Suzanne Keane guides you through the maze that is the perfect wheels   The first step to deciding on your new wheels is to take off one of your existing wheels and look at the back of it to see if anything is stamped on it. You may see something like this “7J x 17 H2 ET35”. 7J – this is the width of the wheel, in this case 7 inches 17 – this is the wheel diameter in inches (you will also be able to tell this from your tyres) H2 – Means the wheel is designed for taking “h” rated tyres ET35 – This is the offset of the wheel, which is explained below. If you decide to change the diameter of the wheels it’s important to check that the rolling radius with your new tyres will match your existing rolling radius (this can affect the readings on your speedometer) – you can check this by using online calculators like this one.  The 3 most important things you need for choosing your alloy wheels are the diameter, in inches, the PCD and the Offset:  PCD – Firstly you need to work out how many wheel studs you have…. but that’s not all! PCD stands for Pitch Circle Diameter which basically means the diameter of the circle of the wheel nuts – so if your car has a PCD of 5×112 wheels that are 5×100 won’t fit. On a 4 stud car you can measure the distance between the centre of opposite wheel nuts, on a 5 stud car this is more difficult but most wheel manufacturers will be able to tell you what PCD your car should be. Keep in mind that not all engine sizes/specs of the same model car will have the same PCD! ET – This is the offset of the wheel – which is the distance in mm between the centre line of the wheel rim and the centre line of the hub (that the wheel fixes on to). In simple terms this is what decides where the wheel sits...