Words and Photograph by Pat CallinanSo, the track you are driving is starting to get a little slippery and muddy. What do you do? First, drop your tyre pressures. This increases the amount of tread in contact with mudder earth (okay, bad joke). Dumping the tyre pressure to about 16psi (or a little higher if you have a big load on-board) increases the tread pattern length. Sure, your sidewalls will bag out a little but that is not why we do it. It’s all about spreading the load and increasing the amount of tread on the ground.
Secondly, lock your 4WD into low-range and activate your centre diff-lock (if you have one). Some will argue high-range, but I’m a fan of low. It provides more torque to the driving wheels, more quickly. Why do we want power? Because the key to many sloppy, muddy tracks is momentum. Tyre treads are quickly blocked up with mud, and the best thing you have going for you is the momentum to roll those tyres over the slop, rather than dig holes through it. Therein lies the key to any successful mud driving. Good throttle control is where it’s at. Too much gas and you will dig holes, too little and your tyres will cake up with goo, grinding you to a halt.
The right tyres will make you look like a much better driver than your ill-equipped mates. Highway tyres (H/Ts) block-up much too easily. They are designed to be quiet and handle well on-road, hence their closed tread. All-Terrain tyres are better, with a more open tread, but they are still not fantastic in mud.
Muddies, or mud-terrain tyres, are what you want. They are bloody noisy on-road, but those open, blocky treads will drag you to the top of Mud Bog Mountain after the others have failed. It is all in the self-cleaning abilities. As the tyre tread gets filled with filth, that mud is quickly ejected, leaving clean tread to clamber up the track. Muddies are not a cure-all, but they’re the next best thing.
Of course, there is another step above a mud-terrain tyre and that is the wonderful world of hardcore tyres. When you hear of brands like Bogger, Claw and Centipede, it’s not hard to understand why. If these tyres were part of your family, they would be the feral ones living in the hills that no one wants to talk about.
Their road manners are worse than mud-terrain tyres but show them a bog hole and they’ll chew it up and spit it out. The best tyre in the mud that I have driven on is the Bogger, closely followed by the more sensible, and on-road friendly, Simex Centipede. Yet, even the world’s most aggressive tyres do not work well if all four wheels aren’t spinning.
Differentials are designed to allow one wheel to spin faster than the other, to let your 4WD turn corners and around bends. If a 4WD’s differentials were permanently locked-in, they would be over-shooting turns all over the place. However when off-road, that differential action causes the wheel with the least resistance to spin. In mud, that can send all of the torque to the wheel that is spinning hopelessly in the slop. Many modern vehicles feature traction-control that senses which of the wheels are slipping off-road and brakes those wheels. Thereby sending drive to the wheels that still have grip.
The first few incarnations of
traction-control in the late nineties are rated awful in my books, as the traction-control response was seriously delayed. By the time the computer had worked out you had lost traction, you were well on your way to bogdom. Worse still, the computer would then brake the spinning wheels, sapping much needed momentum from your rig. The result? One stuck truck.
During road tests, we found that hitting the accelerator at full throttle would only just get you through a section where a traditionally diff-locked vehicle would simply walk through. Why? Because you had to take into account the artificial braking of the wheels through the traction-control system. But (and it’s a big hairy but) it seems manufacturers have finally nutted it out.
Traction-control systems, like that found on modern day 4WD, have come of age and improved dramatically in recent times. They are now far quicker to activate, and many have various modes (mud, snow, rocks, sand etc) to account for the different track surfaces you will encounter. In fact, modern traction-control systems can take you a long way past where your talent has run out.
Personally, I’m still a big fan of the simple old cross-axle
differential lock, like the TJM Pro-Locker, the Maxi-Drive and the ARB Air-Locker. When it gets tough you turn them on and you know they’re on. You can use your eyes and experience to anticipate potential loss of traction on the track ahead, and then engage the lockers where needed. The downside is that they cost roughly $2000 per diff. This does include a compressor though, which can be used to air-up again at the end of the day.
There are cheaper alternatives such as the Detroit Locker, Lock-Rite and the 4WD Systems Lokka, and these cost less than $1000 each. These are automatic lockers and they lock the diff when the speed between the wheels is similar. They can make some noise when they engage and disengage, and are better suited to long wheelbase fourbies. Personally, I prefer them on the rear axle only, as they can engage and make steering heavy if installed on the front.
Of course, most mid to large sized 4WDs feature limited-slip rear differentials as standard. They work okay when the vehicle is new but they quickly deteriorate with age and become ineffective. However, an expert can tweak the diffs, which is a relatively inexpensive way of getting good traction. Go easy here though, or you may compromise on-road handling characteristics.
Enough about traction, what is the quickest way to get out of a bog? Before trying anything, have a good look around your
tyres and your
underbody. If it is just a traction issue, a gentle tug from a snatch strap should see you free. If you can’t see daylight under your fourby, then you could be in trouble. Have a poke around with a long-handled shovel and clear mud from around the tyres and diffs. Again, give the vehicle a gentle tug with a snatch strap or a winch, and try to set it free.
The operative word here is ‘gentle’. If your fourby is well and truly stuck, then it can turn into a dirty big suction cup on mud. Flat surfaces like fuel tanks can suck themselves into the mud, and turn a two-tonne fourby into a six-tonne load. Most straps, shackles and winches simply aren’t rated for that kind of force. In this scenario, you have to break the suction before attempting to drive out or be recovered. You can do this by using an air-bag jack, or a hi-lift jack. This lifts the vehicle, breaking the suction, and allows you to pack rocks or dry material under the tyres, giving you enough clearance and traction to drive out.
If you are using an exhaust-powered airbag jack, try to clear away any sharp debris like sticks from the area that you are placing the airbag. These babies have a tendency to puncture easily. If you are using a hi-lift jack, be sure to use a decent jacking plate, and be careful, as hi-lift jacks are unstable at the best of times. Ensure you pick a good strong jacking point on your vehicle.
Newcomers to the mud-driving game are often tempted to drive off the track, or to the side. It often looks drier, higher and safer but do not be fooled. Once you’re out of the wheel tracks and ruts, you are like a train off the tracks. Your fourby will want to slip and slide sideways where there may be trees. The ground off the main track is often a lot softer and even boggier, which is because the track base has not been compacted by a few thousand fourbies. Stick to the track and you will be better off.
Of course, if it is an emergency and you simply have to drive a difficult track, tyre chains can be a final option. Why only a final option? Because they’ll rip up a track real fast, which only leads to track closures, and no true 4WDer wants that.
Taken from 4WD Monthly, Australia
