Understanding Wheels

Maybe the biggest visual change you can do to your car is change the wheels. Changing the wheel can give the car its character, a set of OZ Ultraleggera would give it that race car look and feel with it's sleek and ultra light weight design, where as the Tansy Daisy might just give it that show car finish perfect for that head turning look we all seek, but the first problem we all stumble upon is well what size do I go for? I don't understand Widths, Diameters and what on earth is offset people keep talking about? Well we wrote this to try and help with that, It's a small knowledge base to help you, but we still have our expert team on hand to give you the advise you need, with the years of experience they have behind them they are there to offer the best fitment advice. So let's start with the first bit of knowledge.

Diameter diagram


Diameter is the most simplest part to find out and work out so a good place to start, The diameter of a wheel is the measurement across from direct opposites in inches, so when we list 15" wheel it is a 15 inch diameter.

You can see what size your wheel is it at the moment by checking the tyre size. you should see 3 lots of numbers written something like this 235/35/19 Ignoring the first two ( We will come to these later ) the last digit reflects your diameter so this tyre size indicates a 19 inch wheel, Simple really! 

When choosing the diameter for your vehicle there is 3 things to consider.

1) "is it going to be too big?" Too big a diameter and you will hit the arch and rub, when going over bumps, turning that sort of thing, so you want to be sure your vehicle can take it, for example you probably couldn't get a 22inch on a 1995 Civic. but a Range Rover has huge arches so would be okay.

2) "is it going to be too small?" The same with going too big, if you was to go to small you could have issues catching the brakes, most modern vehicles come with massive brakes especially any hot hatches or sports cars, So make sure you are taking this into consideration when choosing your wheel.

3) "is it going to look good?" Everyone has personal preferences and it is ultimatley your own decision but there always think about what could look good, think about how far away the arch is going to be from the vehicle do you want the wheel to be tucked away or exposed, if you are unsure then a good place to start is the OE size, most people step it up from there by 1-2 inches depending on use of the vehicle.

Width Diagram


The Width is how wide the wheel is from the face to the back, we measure from the tyre mounting flanges, in most cases the go to is to increase this size over stock, the wider wheels offer better grip and traction and provide better stability this is because a bigger tyre size can now be fitted, and so more tyre is in connection with the road.

However again, things to consider...some of this will be in partnership with the offset, but is too big a width going to come in contact with the suspension, or hit the arch, the ideal fitment is usually to get the wheel flush with the body of the car, this gives it the most aggressive look.

Offset Diagram


Offset is probably the most daunting measurement in wheels to get your head around, but we will do our best to explain! Offset is the measurement from a wheels imaginary centre line to the mounting face. It is most common for vehicles to have a positive ET which means the mounting face is forward of the centre line, this brings the wheel further under the vehicle and closer to the suspension, but some older cars or 4x4's or people with a body kit may be looking at a Negative offset to bring the wheel outwards away from the suspension away from the vehicle.

When choosing offset you need to take into consideration where you might want the wheel to sit, closer to the outside of the car? then look at reducing the number, it is measured in mm so the difference between an ET45 and a ET40 would be 5mm

Zero Offset – The plane of the hub mounting surface is even with the centerline of the wheel.

Positive Offset – The plane of the hub mounting surface is shifted from the centerline toward the front or face of the wheel.

Negative Offset – The plane of the hub mounting surface is toward the back or brake side of the wheel’s centerline.


PCD Diagram

PCD (Pitch, Circle, Diameter)

Maybe the most important measurement, as without this being correct the wheel wont physically attach to the car, the PCD is a "circle" that runs through the mounting holes, you then measure the the size of this circle to get the measurement so a 4x100 would be a 4 stud with 100mm measurement. 

In most cases a quick google will give you the answer, with so many forums and fitment sites it is quite easy to navigate what PCD you have if you was note sure already but this is how to measure it correctly.