Wheel Buying Guide

Advantages of Alloy Wheels

There are numerous benefits to fitting aftermarket alloy wheels to your vehicle. Wheels are usually cast from an aluminium alloy which means they are manufactured as a light-weight product. Given there is a greater selection of designs to chose from they are often far more appealing to buyers than the original wheels fitted to vehicles. Aftermarket alloy wheels are produced in a large range of styles and sizes and catering for most cars on Australian roads. These sizes can range from 13” right up to 24”.

One of the many advantages of fitting alloy wheels to your vehicle (in performance terms) is the reduction in your car’s weight ratio, meaning a reduction in rotating mass at the end of your suspension components. This can assist with improved steering and greater breaking response.

ONE-PIECE & COMPOSITE (2 & 3 PIECE) WHEELS

Wheels are usually manufactured as a single piece structure, however they can also be made up of a two and three piece composite. (Centre, Inner & Outer)

One-piece wheels are usually less expensive to produce as they require no additional assembly. The initial setting up of tools/machines and moulds is quite expensive, but the manufacturing process is much quicker. These wheels are often lighter as there are no extra bolts for the connection of the pieces.

Composite wheels main advantage comes from providing exact fitment to any vehicle. This is often required for older vehicles or those that have a very uncommon offset and stud pattern. Composite wheels often give a vehicle a unique look which will not be found on other vehicles, thus making them highly desirable.

STUD PATTERNS / P.C.D’s

Pitch Circle Diameter (P.C.D) / Stud Pattern

The P.C.D. of a wheel is the diameter of an imaginary circle drawn through the centre of each stud hole. It is typically measured by placing a ruler from the left side of one nut hole and measuring directly across to the left side of the nut hole next to this. This applies for all 4 stud, 5 stud & 6 stud wheels. It is shown as No. of studs / Diameter (mm). E.g. 5/120 means a 5 stud wheel with a P.C.D. of 120mm.

Some wheels are designed as multi-fit wheels where they may have 2 P.C.D’s drilled into the hub centre. This allows for a broader range of fitments within the one wheel. This is normally shown as 8/100-114.3 where there are 8 stud holes to make both 4/100 & 4/114.3 P.C.D’s.

OFFSET

Offset (ET)

The offset of a wheel is the distance in millimetres between the mounting face and the centre line of the wheel.

Positive offset wheels have the mounting face closer to the outside of wheel, forward of the centre line. This will place the wheel further under the car. These wheels generally have very little dish on the outer rim and a small wheel boss on the back of the wheel. Eg. Subaru & Honda

Negative offset wheels have the mounting face towards the back of the wheel, rear of the centre line. This results in the wheel sitting further out from the car. These wheels can have a deep dish on the outer rim and/or a large wheel boss on the back. Eg. Pre AU & 4WD wheels.

Calculating Offsets

• To find the offset of a wheel, first measure the backspace of the wheel from bolt up face to back edge of wheel
• Measure the overall physical rim width (edge to edge) or add 1 inch to the manufacturer’s stamped wheel size.
• Multiply by 25.4 to convert to millimetres and then divide by 2 to find the centre line of the wheel.
• Subtract the centre line measurement from the backspace measurement.
• This will give you either a positive or negative offset measurement.

In most cases, changing the offset of a wheel will increase the loads on bearings, axles, suspension joints and steering components. For this reason it is important to fit wheels with a correct offset to prevent premature wear or suspension failure.

WHEEL DIMENSIONS

Wheel Width
Width of the wheel measured from outer bead seat to inner bead seat. This is not the same as the physical width of the wheel.

Wheel Diameter
Diameter of the wheel measured from the bead seat to opposite bead seat. The physical size of the wheel will be a larger diameter. Centre line Half of rim width measured from edge to edge.

Rear Spacing
The distance from the mounting face to the outside edge of the back of the wheel. This can be measured by placing a straight edge across the back of the wheel and measuring to the mount face. This distance can be used to calculate offsets.

Alloy Wheel Care
The best way to keep your new wheels looking new is to avoid using any car wash wheel cleaners.  Warm soapy water is the best method and should leave your wheels streak free. Make sure to dry straight away.