Alloy Wheel Guide: Get the Basics Here

Presumably, you’re already on this site in the hope of scoping a set of new wheels for your Pride and Joy. If you’re at all curious to know exactly what alloy wheels are, please click here.

Alloys add a great deal to any car. They add to the curb appeal, they’re a great talking point amongst the cognoscenti and they can also add to the resale value of the car. When deciding on the best mags for you, there are basically five key factors that will shape the decision process towards the ones you end up with.

The car you want to purchase them for, the size you want (which will also be dictated to a certain degree by the vehicle), the manufacturer you like the look of. This can be pretty cut and dried, as certain makes and models of car may only be catered for by a small number of alloy brands.

Then there’s the budget you are working to. For instance, it’s quite important that you consider whether you want to retain the tyres already fitted to your car or are happy to purchase new ones, along with the new rims. A not inconsiderable extra expense, if you are upgrading significantly onto low profiles, for example.

The final one is the colour and style you’re after, more than likely guided to some degree by the colour and make of the car and what might suit it best, be they painted, polished, machined, hypersilver or chrome... What’s important here is to ensure that you are getting a size and type which will both suit and fit your vehicle.

Anyone who’s done a little researching into aftermarket rims may have come up against terms such as hub-centric wheels, negative and positive offset and backspacing: all vitally important issues to consider when deciding to exchange one’s standard wheels for something with a little more style. After all, how stylish does one look when a wheel suddenly decides to part company with its parent vehicle?

Don’t be put off by the terminology, get this lot down and you’ll be on route to alloy pro status, at least amongst your mates...

Pitch Circle Diameter

First up its Pitch Circle Diameter also known as Bolt Circle Diameter, that’s PCD or BCD to those in the know. This is the diameter of the circle that passes through the centre of the blot holes. It’s generally measured in millimetres and what you’ll see is something like this: 4x100. Translated this means the wheel has 4 bolt holes and the diameter of this circle is 100mm.

Wheel Offset 

Next up its Wheel Offset, this is the distance from the centre of the wheel cross section to the mounting surface at the back of the wheel. You’ll also see it referred to as the ET and this too is measured in millimetres. Why is it important to know? Well each car has an optimum offset, and range within it’s possible to fit the wheel correctly. Get this wrong and it can affect the steering and suspension of your vehicle. A positive offset will have the surface mounted towards the front of the rim, whilst a negative offset will be mounted towards the back for a concave look

If the offset is too low for the range allowed, the wheel could stick out from the side of the car, if it’s too high from what it should be the wheel could catch on the suspension or bodywork as it will be too far under the car. If you find yourself with an offset that is too high you can use spacers to reduce it. These spacers push the wheel further out until it sits right for the arches and bodywork, meaning you can fit wheels that aren’t made in the direct fitment for your pride and joy. Buy from us and we’ll let you know if you need ‘em.

Alloy sizes

When you’re looking into the sizing of alloys you’ll see it shown like this: 15 x 6.5J. The first half (15) is your wheel diameter, simple enough, while the second half (the 6.5J) is the wheel width. By width we mean the section between the mounting flanges on the wheel.

The Wheel Centre Bore

Finally, there’s the Wheel Centre Bore and Spigot Rings. We’re back to diameters again with the Wheel Centre Bore as this is the diameter of the centre hole in the back of the wheel, and it is crucial to a perfect fit.

Most wheels have a centre bore that is larger than the hub lip which is then supported by a spigot ring locating system. This allows the wheel to be fitted to a wider range of cars. However some wheels are created with a precise fit, these are your Hub-Centric wheels. If a wheel is Hub-Centric it means it has been made with a centre bore to fit precisely onto a specific vehicle, which means no spigot rings are needed.

Where spigot rings are supplied with your wheels it’s essential you use them, unless you prefer a vibrating steering wheel and wear on your tyres and bearings that is.

However, all of these significant and complex considerations have been carefully negotiated and ironed out for you, because we’ve made the whole process totally straightforward here, on our site. Scroll to the top of this page and all you have to do is select the make and model of your car from the vehicle finder and this will produce a display of all the alloys available to that car. You can then finesse your choice by brand, colour, style and price.

Thereafter, we also provide the tyre options available to you, for that particular alloy choice. What could be simpler

Don’t be afraid to pick up the phone (01274 936040) and talk to an expert, if you’re at all unsure about how to proceed, what size wheels will fit your car, anything at all. It’s what we deal in, day in day out.