Secondly, the tyres should not be more than 50% wider than the manufacturer`s widest option, the rims should not exceed the recommendations for the correct assembly of the tyre, and the wheel track should not be wider than 50 mm, ensuring that the wheels remain in the body and maintain the distance from all components and panels. If you install a set of high-performance wheels and tires in a standard vehicle, it is also necessary to install the appropriate chassis components – springs, shock absorbers and stabilizers – from the manufacturer. `Total original diameter` means the maximum outer diameter of the largest tyre specified by the original manufacturer of the vehicle as an option for the vehicle, as indicated on the vehicle tyre plate. When installing new rims, regardless of their size, the wheel and tyre combination must first comply with Australian design rules for road traffic and must not have a complete circumferential weld bead other than the one that attaches the centre of the wheel to the rim itself. Over time, the wheel size of passenger cars has increased significantly, with some high-performance vehicles now equipped with rims up to 22 inches in diameter as standard. As a result, the tires are wider and have lower sidewalls. However, in any case, spare tires must be legal for road traffic (i.e. no racing slicks), manufactured with the same construction as the original tires (i.e. radial tires) and the nominal load is not less than the minimum load capacity prescribed by the manufacturer, which is indicated on the tire poster. Especially for passenger cars, when replacing tires – even if the wheels are the same size as the standard – the speed class of the tire must be at least one designation S (suitable for a minimum maximum speed of 180 km / h). First of all, the minimum speed for off-road tires is N (with a minimum maximum speed of 140 km / h).
But first, check your vehicle`s tire poster for the manufacturer`s minimum speed, as most modern 4×4 off-roaders are more powerful. And finally, there is a little more thanks to increasing the roll diameter of off-road tires, which should be no more than 50 mm larger or 26 mm smaller than the original tire. Example that does not require certification: replacement of type 215/65R17 tyres (total diameter of 712 mm) with type 235/65R17 tyres (total diameter 738 mm), increase in total diameter by 26 mm or 4%. Tip: To determine if the tires you select require certification, you must examine the tire plate that has been applied to the vehicle by the manufacturer. Sometimes the tire plate displays more than one tire size, so optional tires of that size can be mounted. If one of the tyre sizes indicated on the poster (e.g. 215/65R17) matches the marking on the sidewalls of the tyres, certification is not required. So, if you want to attach new boots to your car, let`s find out how far you can go by mounting different wheels and tires. As with the shoes you wear, upgrading your car`s wheels and tires is an easy way to beautify the appearance and improve driving dynamics. If the wheels are wider, they must not be wider by more than 30 % than the largest optional tyre installed by the manufacturer and must be included in the vehicle body as before. One of the main important points for 4WDer is the one about changing the size of the tire. The new documentation takes precedence over the previous rules and states that the total diameter of tires can be increased by 7% before certification by an engineer is required: similarly, no part of the wheel or tire in any operating condition must touch any part of the bodywork, chassis or steering, brakes or suspension, and the wheels must be included in the body (including all flares), if the wheels are aligned in a straight line.
But the real “guys in blue” can write you a ticket – or worse, fight with a non-roader and confiscate the car – if you don`t follow clear rules for vehicle modifications when installing different wheels and tires. Wheels are considered illegal without a separate design certificate if the brake calipers, hubs, suspension and steering components need to be modified in any way. Finally, the consequences of installing different wheels and tyres shall not increase the total width of the vehicle lane (the distance between the vehicle and the centre of each tyre) by more than 25 mm above the maximum value specified by the vehicle manufacturer. For example, it is allowed to have a 235/45 front tire and a 275/35 rear tire, while mounting a 295/25 rear tire would be illegal. Similarly, the significant increase in the popularity of recreational off-road driving has been a boon for all-wheel drive modifications and the assembly of special 4×4 wheels and tires that go against the road trend: smaller rims with balloon rubber that are better suited for off-road use. Changing the diameter of the roller affects the accuracy of the speedometer – larger wheels make the speedometer slower than your actual speed on the road, increasing the risk of being reserved for speeding, while smaller wheels do the opposite – and there is a legal requirement for the wheel and tire combination to maintain the level of accuracy in ADR 18/03. In special circumstances, such as classic cars, the speed rating can only be lower if the tyre is higher than the maximum speed of the vehicle. However, this requires permission from your state`s registration authority. Example subject to certification: Replacement of 215/65R17 tyres (total diameter 712 mm) with type 265/65R17 tyres (total diameter 776 mm), increase in total diameter by 64 mm or 8%. “Replacement of tires that change the total diameter of the tire by more than 7% of the original total diameter. When the wheels and tyres are enlarged, the total diameter shall not be more than 15 mm or 26 mm smaller than the tyre size specified by the manufacturer for the respective model.
Basically, the same principles apply to the assembly of wheels and 4×4 off-road tires for specialists to ensure the integrity of vehicle safety. And if you vary the aspect ratio (the ratio of sidewall height to tread width) of the tires between the front and rear axles (i.e. wider rear tires with a lower profile), the variance should not be more than 10%.