Those who enjoy heading off the beaten track in their 4×4 know that even the most familiar tracks can present you with unexpected conditions. Whether you’re up against a steep incline, uneven & rocky terrain or a slippery muddy track, being able to take advantage of traction is one of the most important elements.
In a vehicle with open differentials in 4WD mode, drive can only go to two wheels at any given time. At the flick of a switch, an ARB Air Locker can send equal drive to both wheels on an axle allowing you to take advantage of the wheels that have traction and push forward along the track.
Learn more about ARB Air Lockers, traction, drive and everything in between below.
In simple terms, traction is the resistance between your vehicle’s tyres and the ground which offers you, as the driver, control of the vehicle; no traction = no control.
Drive is the delivery of torque and power; drive (with an appropriate amount of torque force) is what rotates our wheels and tyres against the track’s resistance.
Tyres, their tread pattern and construction are one of the most important factors to the performance for your 4WD. Your tyres are the final piece of the puzzle in transferring the engine’s energy to the track so that the car can move forward.
Tyres, however, are only able to move the car forward if it least one tyre can gain traction to the track surface and that tyre is also receiving enough drive (torque) from its respective differential.
The fact is, you will never be able to control the traction of the track surface, but you can control the type of tyres, the foot-print of your tyres (air pressure) and whether your tyres receive drive or not. All these things will hugely improve the likeliness of finding and maintaining traction.
If there is no traction on the surface, you can have 4 wheels spinning and little to no forward momentum. So the first steps to improving traction are:
Reducing tyre pressure (letting air out) increases the surface area that the tyre has in contact with the ground; more tyre on the ground means better load distribution and more track surface to get traction from. This is most important when driving on sand. The benefits of low tyre pressure can also be seen when navigating rocky terrain, where the tyres have an increased ability to shape themselves around objects on the track, helping us gain more traction.
Your 4×4 has a front differential and a rear differential; a differential is designed to distribute drive to either the left or right wheel on each axle.
Delivering drive to just one side of the vehicle is what allows your left and right wheels to spin at different speeds, which is imperative for on road cornering.
By design, a diff will rotate the wheel with the least traction. So, when we are travelling off road, if one wheel is suspended in the air or is sitting on a very slippery surface, the differential will only delivery drive to the wheel with no traction.
This works against 4WDers because you can very easily find yourself in a situation where one wheel on the front axle and one wheel on the rear axle has little to no traction. In this situation, neither of the wheels with traction will receive drive.
A selectable differential locker is a full replacement differential which can be ‘locked’ by activating a switch from the driver’s seat.
The locking function removes the differential’s usual capacity to split the drive left to right by binding the gears; this means that both wheels will always rotate at the same speed, until the locker is disengaged.
We’ve described the basics of how a standard differential works and why we need them on road, however, when it comes to 4WDing, it can cause issues when driving on uneven or muddy terrain, where it is common for one or more wheels to slip or become raised off the ground.
The perfect time to engage a diff locker is when traversing low traction surfaces, whether they be slippery or overly uneven causing wheels to lift.
Switching the differential to ‘locked’ will send equal drive to both wheels, meaning that both the wheel off the ground and the one firmly planted on the ground will have equal drive, allowing the wheel with the most traction to push you forward and continue on the track.
We need a locker to make effective use of all the traction available between our tyres and the surface of which we are driving on. Lockers give you the ability to take advantage of the traction that is available by supplying drive to all wheels.
For example, when you are in 2WD mode, you have drive going to one of your rear wheels, giving you 25% of all available drive. Engaging 4WD mode will send drive to one of the front wheels also, giving you 50% of all available drive, this is where lockers come into play. Engaging your rear locker will send drive to both rear wheels, coupled with the drive going to one of the front wheels, will give you 75% of all available drive. Engaging the front locker with the rear locker will send equal drive to all 4 wheels, giving you 100% of all available drive.
The main benefit that an Air Locker has over an electronic-locker is its instant activation. By comparison to the majority of electronic lockers, an ARB Air Locker engages instantly and at any speed; furthermore, an ARB Air Locker has no operating speed limitations.
Being able to engage your locker ‘on the fly’ means you don’t need to lose your momentum before tackling an obstacle.
Having an on-board air compressor has many advantages other than a way to activate Air-Lockers. On-board compressors are also perfect for inflating tyres, cleaning car components such as door seals and air filters, inflating air beds or for basically anything that needs compressed air. Having on-board air becomes very handy to have in your vehicle, especially considering that you don’t have to find space to pack it, nor do you need to pull it out and connect it to your battery every time you need to use it.
A comprehensive guide to vehicle specific Air Locker applications and part numbers.
For the full range of spare parts available for ARB Air Lockers, please download our Service and Parts Manual.
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