Johann Viljoen presents his column Shop Talk, he talks everything 4x4

Shop Talk: Tyre Tread

In the manufacturing process, the tread compound is possibly the most variable, gets a lot of attention from the compound scientists, and is fine-tuned to the application of the product. Mud- and all-terrain tyres that deliver excellent traction, for example, cannot be expected to deliver the tread mileage of a tyre engineered to operate only on paved surfaces. The tread is just one of the 7-11 compounds that make up a tyre, with each one applicable to a specific task − from holding together the various layers of nylon and polyester, to encasing the bead wires, or ensuring that the

Shop Talk: Sidewalls & load ratings

Serious 4×4 tyres offer a 3-ply sidewall, which will obviously be stronger than a 2-ply. The major benefit is the puncture-resistance added to the vulnerable sidewall and tread areas. In a normal 2-ply radial tyre, each ply runs at the same 90-degree angle from the bead. The rubber gaps between the sidewall cords are the weakest point of a tyre. A nail, stake or thorny bush can push against the sidewall cord, be deflected, and penetrate through the weakest point (the rubber), resulting in a puncture. In the case of Cooper and Mickey Thompson tyres, the 3-ply sidewall forms a

Shop Talk: Tyre load ratings

Tyres (and the air inside them) are totally responsible for supporting the weight of the vehicle. If the load rating of the tyre is insufficient for the vehicle which it is fitted to, the tyre may become overheated, resulting in potential tyre failure. For example, if a passenger-car tyre is selected to replace an OE light-truck tyre on an SUV, the new tyre must meet, or exceed, the requirement for the specific vehicle weight. In order to determine, roughly, the load capacity for each individual tyre, identify the gross weight of the vehicle and divide this by four. If the gross weight of the vehicle is 2040kg,

Shop Talk: Tyre construction basics

Tyres look simple enough from the outside, but the mix of components inside is the result of extensive (and expensive) research and development by the tyre manufacturers. Each tyre type and profile is designed to meet a specific and exacting set of requirements, either set down by the vehicle manufacturers (when the tyre is specified as Original Equipment) or to meet a defined range of demands that make it attractive as an aftermarket fitment. All the components of a tyre work together to meet a specific set of requirements, and consumers need to know what their requirements are, and what

Shop Talk: Under the skin

Tyres are designed, manufactured and tested to meet strict governmental requirements, manufacturer requirements, vehicle performance characteristics and consumer expectations. That is a lot of expectation. Modern tyre technology blends a unique mix of chemistry, physics and engineering to give consumers a high level of tyre performance in the areas of safety, reliability, efficiency, long wear and comfort. Tyre use however is to some degree out of the hands of the manufacturer, so if consumers want their tyre service life to match the cost, it’s best to maintain a proper schedule of tyre care, which means regular balancing and rotation. Construction

Shop Talk: Wheel Alignment

Simply put, wheel alignment refers to the adjustment of the wheels angle perpendicular to the ground and parallel to each other. Well aligned wheels will ensure stability and a vehicle that tracks straight along a flat road. To ensure maximum stability and tyre life, wheel alignment must be adjusted relatively frequently and can be affected by bad road surfaces or a hard knock. Below, we have listed some factors of relating to wheel alignment and their effects. Camber: This is the angle of the wheel, measured in degrees, when viewed from the front of the vehicle. If the top of

Shop Talk: Types of tyre damage

Whether or not you have obvious damage like a puncture, it is always important to inspect your tyre after every 4×4 trip to check for cuts, chipping and sidewall damage. Heat damage: Driving for extended periods at low pressures, such as on a long dune trip through Namibia, will cause a surprising level of heat build-up along the sidewalls of the tyre. Heat is created because the rubber, canvas and wire elements in the tyre flex and potentially delaminate. The risk here is that severe tyre damage may not be visible, as strands of tyre break within the tyre. Look

Shop Talk: Tyre Rotation

Rotation will prolong tyre life and help maintain balanced handling and braking. This is particularly important when using all-terrain or mud-terrain tyres whose bigger-block pattern is subject to added heel and toe wear when used on tar. What is the correct tyre rotation pattern for a 4WD vehicle? I often find my customers only do their rotations when servicing their vehicles. This is not enough. On a four-wheel drive subject to many additional stresses, and varying loads, more frequent rotation is better – not every 10 000 to 15 000km, rather every 5000-6000km. Every tyre carries a different weight and front tyres

Shop Talk: Upsizing your tyres

What happens when you upsize your tyres? Johann ‘Tyres’ Viljoen tells you what to expect. Changing the diameter of a vehicle’s tyres can dramatically affect the performance of the vehicle − from acceleration, to braking, to fuel economy. By changing to a larger diameter tyre, a 4×4 vehicle can reduce its fuel consumption by as much as 15%. However it also impacts on the engine’s torque curve as well as the vehicle’s weight, aerodynamics, suspension and gearing. A more aggressive tread also has an influence. A larger diameter tyre covers more ground per revolution so overall gearing is reduced, causing

Shop Talk: Tyre width vs tyre profile

Johann ‘Tyres’ Viljoen tells us about tyre width vs tyre profile, and how to achieve an optimum tread footprint off-road When fitting an off-road tyre, it’s important to remember that fitting a wide tyre with a low profile on large rims will not benefit your vehicle off road. It’s much better to have a tyre with a tall profile on smaller rims with a narrower width section. Narrow and tall tyres allow you to deflate more in off-road situations like sand or mud, which lengthens your footprint to improve braking, traction and stability. Very wide, low-profile tyres are easier to

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