How to: Changing wheels on your 4×4… what you need to know
If you want to spruce up your rig with a new set of wheels there are a few important technical requirements and legalities you need to be aware of.
THERE ARE several reasons you might want to fit a new set of wheels to your 4×4. The obvious one is aesthetics, and there’s no denying a set of shiny new wheels can instantly transform the look of your vehicle giving it more on- and off-road cred.
There are also more practical reasons, such as upgrading from a set of old steel split-rims to one-piece wheels that will accept tubeless tyres, or fitting a set of wheels that will accept a specific tyre size. Some four-wheel drivers will also upgrade their wheels and tyres to match their trailer, while others will have a set of standard rims for on-road duties and a set of aftermarket rims fitted with mud-terrain tyres for off-road driving.
No matter the reason for upgrading to a set of aftermarket wheels, there are several things to take into account when deciding on what rims are best for your rig. After all, you don’t want your vehicle to be unsafe, or to fall foul of the law or your insurance company.
Steel or Alloy
Even before you’ve started to browse online wheel catalogues, chances are you’ve already decided whether you’re going to fit steel or alloy wheels to your vehicle. This decision may have been primarily about aesthetics, or it may have been a purely practical one.
Other than their shiny, flash appearance, the obvious advantage of alloy wheels is they’re lighter than steel wheels. This not only makes them easier to handle when you have to perform a tyre change, but also reduces your vehicle’s unsprung weight, which can benefit ride, handling, on-road performance, braking and fuel economy.
Although alloy wheels are very strong, they are also very hard, and if they cop a big hit off-road they can crack. And unfortunately, a cracked alloy wheel can’t be repaired, rendering it useless.
Steel wheels are better suited to off-road driving; they are tough and if they cop a hit off-road and are bent out of shape, they can usually be bashed back into round with a hammer, without affecting strength to a great degree.
On the downside, steel wheels are heavier than their alloy counterparts and they’re not as aesthetically pleasing to some, with only basic designs available. But if you intend to do a lot of off-road driving, particularly in remote areas, then steel is the best option.
Stud pattern and offset
For an aftermarket wheel to fit properly to your vehicle it must have the correct stud pattern or PCD (pitch circle diameter). In the case of many 4x4s the PCD will be listed as 5×15, 6×114.3 or 6/139.7. The latter, for example, is the PCD of a six-stud Toyota HiLux; the ‘6’ refers to the six studs and the 139.7 refers to the PCD in millimetres, which is basically the diameter of an imaginary circle drawn through the centre of the wheel’s bolt holes.
The wheel offset is also an important consideration. The offset is the distance from the wheel’s hub-mounting surface to the centreline of the wheel. A wheel with zero offset means that the hub-mounting surface is even with the centreline. A wheel with positive offset has the mounting surface closest to the outside face of the wheel, and a wheel with negative offset has the mounting surface closest to the inside of the wheel.
If your vehicle’s standard wheels have zero offset, for example, and your new aftermarket wheels have negative offset, the new wheels will increase the vehicle’s track. If the track is increased in this way by more than 25mm it may increase the loads and stresses on the vehicle’s axle and other components, as well as affect handling and potentially cause the wheels to interfere with the vehicle’s bodywork. For this reason, a track increase of more than 25mm due to a wheel offset change is not legal in most states.
It should also be noted that the use of spacers between the vehicle’s hub and the wheel’s mounting surface to overcome offset discrepancies is not legal unless the vehicle manufacturer specifies them as original equipment.
The laws pertaining to allowable wheel sizes vary around Australia, so you should check what is legal with your relevant state registration authority.
Most state road authorities don’t allow the fitment of wheel and tyre combinations much bigger or smaller than the vehicle’s original equipment set-up. In NSW, for example, you’re not allowed to fit tyres that are more than 26mm wider than the largest optional wheel recommended by the vehicle manufacturer, and the overall rolling diameter must be no more than 15mm over the largest wheel and tyre combination specified for that vehicle, nor 15mm smaller than the smallest wheel and tyre combination fitted to that vehicle. And, as mentioned, the fitment of aftermarket wheels must not result in an increase to wheel track of more than 25mm. Wheel and tyre combinations that exceed these guidelines require the vehicle owner to source an engineering certificate.
There are a lot of rules and regulations pertaining to the fitment of aftermarket wheels and tyres, but fortunately there are also a lot of experts out there who can help.
Most reputable wheel and tyre outlets, along with most four-wheel drive specialist outlets, will be able to point you in the right direction when it comes to fitting a new set of rims. The latter will not only be able to help with legalities, but also offer advice on what wheels and tyres will best suit your needs depending on your vehicle and the type of driving you subject it to.