Alloy Wheels

Before you start shopping, you’ll need to know your cars PCD pattern. PCD stands for Pitch Circle Diameter, this tells you the number of studs your wheel hub has and the distance between each stud.  

For example, a 4 x 100 PCD pattern means your wheel hub has 4 studs and they are 100mm apart. For the MX-5 NA, NB & ND you’ll be looking at a 4 x 100 PCD. The NC is the odd one out, taking its stud pattern from the RX-8, using 5 x 114.3.

Wheel widths are usually written on the wheel itself as a number and J, for example, 8J. In this case, J just means inches. So if your wheels say 8J you’ll want a width of 8 inches. 

Another important figure to know if offset. This is the distance between the center-line of the wheel and the hub mounting face and is expressed as positive or negative. For example, if a wheel has an offset of ET20, it means the wheel hub face will be 20mm away from the center-line. 

Since this figure is positive, the hub mounting will be closer to the outer edge of the wheel. If the offset was ET-20 (negative 20), the hub face will still be 20mm away from the center-line but in the other direction. Making the hub closer to the inner edge of the wheel effectively pushing the wheel away from the car. Be careful not to go too low, as if you push the wheel too far out the tyre will start to rub against your arches.

The stock MX-5 wheels have an offset of around ET40 (this differs 1 or 2mm for sport models), making the wheel hub mounting face closer to the outer edge of the wheel. In order to keep your tyres from rubbing against the arches, you’ll need to know the minimum offsets and maximum widths you can run, this changes depending on the model. 

NA – ET30 / 7.5J

NB – ET20 / 8J

NC – ET40 /  8J 

If you’re looking at alloy wheels that are wider or have a lower offset, you’ll have to modify your arches. The amount of modification you’ll need to do will depend on how low your desired offset is. This can range from a slight roll to get a few extra mm to fitting wider fenders to get a few extra inches.