4x4 Glossary
From A-Z: All you need to know about 4x4 cars, tyres and beyond.
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2023/06/21
Be prepared for anything concerning the challenges of off-road driving.
When driving on a proper road, the vehicle’s manufacturer usually indicates the correct tyre pressure in the user manual. When driving off the road with a 4X4 vehicle, one question will arise: ‘What should my tyre pressure be under these very different circumstances?’. The recommended tyre pressure for the highway is different from the off-road tyre pressure. In order to have the best traction possible, you must choose the correct tyre pressure and shorten or lengthen your tyre footprints, according to the terrain. To do so, please be careful, assess your environment and inflate or deflate your tyres as followed:
- On rough, terrain, approximately 10% under-inflation should be used
- On loose ground, deflate the tyres to approximately half (50%) of the standard pressure
- Over sandy terrain, favor one quarter to nearly half (25-40%) of normal pressure
- In snow or mud, more than about a third (30%) deflation of the recommended pressure is not advised
With a tyre pressure check make sure that you are using the correct tyre pressure for each soil condition. If you wonder ‘what should my tyre pressure be?’ please always remember that dropping the tyre pressure to less than a half (50%) is not recommended for most situations. These data are general industry guidelines which have to be taken into consideration for recreational driving. Be sure to always reinflate your tyres when going back on the highway, as it is important to always adjust the pressure to changing driving conditions. If you forget to do so, the stability of the tyres could be impaired or it could result in an increased braking distance.
We recommend to frequently check your car details in a complete vehicle check to minimize the risk of unexpected events. Just follow our vehicle inspection checklist. Start with your tyres and inspect any signs of damage. Continue with a tyre pressure check. Always check the pressure when cold. Low tyre pressure can result in an increased braking distance. Always bring a tyre gauge and compressor. Moreover, with a fuel check ensure that you have enough fuel for the duration of your journey. This precaution also applies for all the fluid levels (have spare for topping up on longer trips).
With your vehicle check it is also important to know the limits of your vehicle and its accessories (as well as any electronic systems such as traction and stability control, hill descent control and differential locks).
What is gear? Basically, ‘gear’ describes any rotating machine part with cut teeth. What is a gearbox then? A gearbox provides speed conversions through gearbox transmission. For serious off-road driving, it is advised to equip 4x4 vehicles with a two-speed transfer gearbox. With proper transfer gearbox mounting a transfer 4x4 gearbox will send drive to the rear and front prop shafts and allow you to select either “High” or “Low” range gears in a gearbox for off-road driving.
- With a part-time 4x4, the following options are available: high-range 4x2 (2H) gearbox, high-range 4x4 (4H) and low-range 4x4 (4L)
- With full-time 4x4 vehicles, only two options are available: high-range 4x4 (with center diff open/locked – if fitted) and low-range 4x4 (with center diff open/locked – if fitted)
In off-road 4x4 driving high range 4x4 is recommended for soft or slippery conditions, such as sand, dirt and muddy roads. While full-time four-wheel drive vehicle have 4x4 permanently engaged, on part-time vehicles, changing to off-road 4x4 requires shifting from 2H to 4H.
Low-range 4x4 should be engaged in difficult conditions, such as rough or rocky terrain, steep gradient. While reducing the vehicle speed, it will provide the torque required in such difficult off-road 4x4 driving. Be sure to select this mode, when the vehicle is stationary and stable because it could otherwise result in a loss of control or damage the vehicle.
If your car is stalling while an off-road hill climb, the vehicle will be in gear with the engine switched on but stalled. If your car loses power while driving up hills like this, it is recommended to perform a Hill Stall Recovery for manual vehicles.
Start by switching the engine off and placing your foot firmly on the brake. You may then depress the clutch and select the reverse gear in low-range. Slowly take the foot off the clutch and off the brake, one step at a time. The vehicle will then be in reverse gear with the stalled engine stopping it from rolling down the hill. After you made sure that the back track was clear, start the engine and keep your feet off all pedals. It will result in a smooth downhill progression.
When it comes to automatic vehicles, simply place your foot on the break, select the appropriate gear and slowly take your foot off the brake.
The first thing to do, when your car got stuck in mud, is to stop the engine, otherwise your risk to dig the vehicle in even further. How to get a car out of mud? Try digging away any mud in front of the wheels and place items such as car mats, or even branches under the wheels to give you traction. These two steps should make the car stuck in mud recovery manageable.
Alternatively, try to gently move the steering wheel from side to side when your car is stuck in mud. This can give the tyre sidewalls a chance to get a foothold.
The car’s suspension controls the vertical wheel movement and maintains contact with the ground. These systems vary according to the vehicle, manufacturer, model, etc. The two main 4x4 suspension systems are the following:
- The independent suspension: this off-road suspension allows each wheel to move independently of the opposite side wheel. Although it provides good road holding, comfort, handling and stability, its design results in variable ground clearance relative to the differential. Several moving parts could be prone to damage during extreme off-road driving.
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- The solid beam axle: usually used for light, medium and heavy vehicles, both wheels are connected with this 4x4 suspension. When one wheel moves up, the opposite wheel moves down, maintaining clearance bellow the axle over rough ground. By means, with this car suspension moving parts are protected from impact and damage when driving off-road.
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You should pay attention to the entry and exit point of the obstacle. Make a visual inspection, ensure correct gear selection and use of high-low-range and diff-lock, but also understand the ability of your 4x4 vehicle. It is also essential to maintain momentum and traction through the obstacle. And if your vehicle stalls, use the foot brake to ensure the vehicle stalls in gear.
Be sure, for each obstacle, to select the corresponding plan of action, tactics, procedures and what to do in case of an emergency.
When venturing off-road, it is essential to have a basic set of items for car recovery. This includes gloves, bow shackles, snatch blocks, recovery equipment (straps, chain or extra cable), tree protector, load straps, towing points on your vehicle (front and rear), spade and axe.
- Recovery straps: the straps should be attached with bow shackles to recovery points as the tow ball or goose neck have an insufficient load rating for recovery procedures. Once the shackle is rigged and totally tightened, slacken the pin slightly to make it easier to release after the recovery. Before you begin the procedure, make sure that the area is clear of passengers, bystanders and any obstacles. If needed, clear mud or sand from under the vehicle.
- High-lift Jack: be aware that you should only use a high-lift if you are trained properly as it can be really dangerous. While useful in a variety of situations (used as a jack, a small winching device and a vice), it requires the fitment of secure jacking points on the vehicle. Moreover, always use it in conjunction with a stable base plate to provide a more secure footing that spreads the load over a greater area.
- Air jack: it refers to large bags made of PVC that are filled with air from the exhaust and can quickly lift the vehicle for car recovery. Expensive, but lightweight and easily stored, you cannot expose it to any hot vehicle components or to sharp objects.
Winching: While keeping the area clear of passengers, drape a blanket over the winch strap to reduce the injury risk if it snaps. Be sure to use an attach point that can withstand the strain.
Before using your car for crossing a river, you must know how low your air intake and breather pipes are situated. Before a 4x4 river crossing it is also important to observe your surrounding terrain to get a fair idea of what you should expect in the river bed. If you plan to use your car for crossing water, you should know about the safest river crossing techniques. Ideally, you should do your visual inspecting by walking through the water and assessing the ideal route (away from deep and/or fast-flowing water at best).
How to cross the river: Make sure to plan your exit point in advance, to keep your windows open and to remove your seatbelts. You may also find it more convenient to cross the river at an angle that is slightly against the flow, as that would give you additional time to respond if the water starts pushing your vehicle. Be aware that you should never switch off the engine when stationary in the water and that you should maintain a steady speed all along during car-crossing a river.
Driving on the road a high-end winter tyre beats even a good all terrain tyre on snow and ice. The winter tyre is the specialist. The all terrain can perform in winter conditions but it depends on the product itself. Which all terrain (AT) is the best choice? An all terrain tyre like the Grabber AT³ is performing well in snow. It has even the “Three-Peak-Mountain-Snow-Flake” (3PMSF) symbol. A tyre with this symbol is fulfilling certain legal requirements for winter tyres and is performing well in winter conditions.
In deep snow you can even optimize your performance with an all terrain (AT) tyre by making sure that you implement more than about a third (30%) deflation from recommended pressure.
Generally driving off the road the picture is quite different. All terrain tyres will beat winter tyres in most situations.
Momentum in cars is an important off-road notion. What is momentum? In physics momentum describes the product of mass and velocity of an object. Here a momentum example, when driving: When you have little traction, you will find it much more difficult to move forward from a dead stop. The key is to find the right balance between traction and momentum: not too slow to risk getting stuck, not too fast to risk having an accident.
As for the weight transfer, please be aware that every angle surface you drive over has consequences on your weight transfer. It will shift from one end to the other and from one side to the other side. For example, when you are driving uphill, the weight will undoubtedly shift to the rear tires. To understand momentum of cars, you must know your vehicle and adapt your driving skills to the road you are facing to avoid rolling over.
When it comes to shock absorbers in a car, you have three choices: coil springs, leaf springs and torsion bars. If you are using a solid beam axle, you may prefer using leaf springs, while coil springs and torsion bars are more often used with an independent axle.
- Coil springs are known for absorbing vibrations better than leaf springs but are considered less practical because of their installation. They are often preferred for high performance trucks because they allow more movement within the suspension system. They offer more comfort and handling.
- Leaf springs are a kind of shock absorbers that are known to be sturdier than coil springs. They allow you to carry much higher loads with less deflection.
- Torsion bars don’t flatten out or compress like leaf springs or coil springs because they consist of a narrow steel tube.
A shock absorber for your car is essential while driving. When you are going off-road on rough surfaces, they are working constantly. Be sure to choose your absorbers as to procure the best safety level and control your vehicle.
When off-roading, you probably have already been in a situation where your car broke down. Therefore, you should always have a car emergency kit and spare parts in your vehicle. A well thought through off-road equipment really is key, if you end with a broken car. This list includes fuses, fuel filter, tow bars, electrical fuel pump, recovery materials, spare drive shaft and universal joints and much more. If you have no idea what you really need to take with you, in order to be prepared when your car broke down, please, contact an off-road expert who can advise you.
You should always be aware of tyre speed rating! Tyres can go really fast but be aware that each product is different. Depending on the tyre size and the load index, the speed index will be adjusted for your safety. As an example, the GRABBER AT³ (Serie 40 – 275/40 R 20 106V XL) can be driven up to 240 km/h.
Where to find speed rating on the tyre itself? It is displayed on the sidewall at the end of the tyre’s size and is represented by a letter. A speed rating “Q” can go up to 160 km/h, tyres with speed rating “V” can go up to 240 km/h.
It is always essential to adjust your speed to your environment. Do not use your full speed, when there can be danger around the corner or straight ahead of you. Having a maximal speed index doesn’t mean you have to max it out.
