Off-road driving tips

[Peter Connan]

There appear to be many people who are scared to self-drive due to a lack of experience in off-road driving.

 

But for the most part, self-drivers are not allowed to go truly off-road (at least not in the areas I have travelled), thus self-driving will be mostly on roads (and in fact the vast majority of driving will be on tar roads).

 

And while some dirt roads can become truly impassable at some times of the year, for the most part it's not that hard. So in the hope that this may encourage some to experience the adventure, here are a few ideas, tips and tricks:

 

Firstly, when you collect your hire 4x4, make sure it has a spare tire, and that that spare is inflated. Of course, it will be useless without a jack and a wheel spanner. Make sure you know where they are. In sandy areas and some types of mud, make sure you have a compressor. If the vehicle doesn't have one, buy one in the city you picked the car up in. Try to get one with at least 70L/min capacity.

 

Also, familiarize yourself with the 4x4 controls. I am going to assume from here on that the vehicle is a "normal", fairly modern 4x4 car or pickup truck/LDV. These will normally have a selector to select between 2 wheel drive (usually rear wheels), 4 High and 4Low. Basically, 2WD is used most of the time. 4WD is used if traction is likely to be a problem. I believe it also reduces fuel consumption in soft sand, but it should probably not be used at high speeds (the owner's manual may have specific information but I would say not over 80km/h). The difference between Low and High is the gear ratio. Low range gives you the ability to tackle difficult obstacles more slowly and with more control, and gives more torque at the wheels. It is used for very steep inclines, very thick and soft sand, thick mud, deep water crossings and any time you want to go really slowly.

 

On dirt roads, tracks tell stories.

Take note of what tracks are on the road. If vehicles have passed by, the chances are the road is passable. You can also get a pretty good idea of how much traffic a road is subjected to. But be careful if the only tracks you see (especially in muddy or sandy situations) are the distinctively wide and aggressive tracks of large mining or military vehicles. These vehicles have much more ground clearance than most hired 4x4's and can really churn up a track to the point where it is impassable to such vehicles.

 

Let's talk specifically about sand:

The first step is to reduce the tire pressures. Many people seem to be scared to do so, but in sand this is the biggest single differentiator between success and failure. Lower tire pressures will also improve comfort and reduce track damage. And contrary to popular opinion, it reduces the chances of getting punctures.

Basically, reducing tire pressures increases the size of the vehicle's "footprint". This in turn reduces the "ground pressure", in other words, the vehicle is more likely to ride on top instead of sinking into the sand.

 

 

As you will see from the above image, at first there is very little effect but as the pressure is reduced further the effect is magnified.

Do not deflate to 1.8 Bar and think you have done what you needed to. In thick sand, 1 bar should be seen as the absolute maximum. If you still struggle, go down.

 

Of course, there are no free lunches. Running tires at low pressure does have some significant disadvantages. Firstly, at higher speeds the vehicle will be less stable, and avoidance maneuvers can cause the vehicle to roll over. Secondly, at very low pressures there is a chance of "de-beading", or popping a tire of it's rim. This happens only if a side load is applied, so when running low pressures, avoid fast, sharp turns. Lastly, tire life is reduced, and tires can heat up. If driving long distances in soft sand it is good practice to check the temperatures every hour or so. If it burns your hand, either inflate or rest a while.

 

I have however used tire pressures as low as 0.35 Bar for extended periods, and none of the above should be a significant problem at the speeds you will do in thick sand at 0.8-1 Bar.

 

If you do suffer a de-bead, as long as you have a compressor it's not a serious problem. Jack up that wheel, and clean the bead (be careful of your fingers). Mix up a mug-full of strong dishwashing soap solution and connect the compressor. When running the compressor, run the vehicle's engine as well to prevent flattening the battery. Apply the soap solution to the bead to act as a lubricant, and move the outside of the tire around, pulling it against the bead wherever you see bubbles forming. keep going until the tire seats (which is normally accompanied by a pretty loud bang).

If you can't stop the leak, tying a ratchet strap around the tire and tensioning it might help, or else remove the tire from the vehicle and rest it against one of the other wheels at a 45 degree angle, pushing downwards on the rim.

 

While in sand, as already mentioned avoid sharp turns, and also avoid using the brakes aggressively. If you have trouble pulling away after stopping, reverse a short distance, then try again.

Never spin the wheels. If they start spinning, stop, reduce the tire pressures further and try again.

Edited April 22 by Peter Connan

[offshorebirder]

14 hours ago, Peter Connan said:

If they start spinning, stop, reduce the tire pressures further and try again.

 

Or pull out your sand ladders!

[Peter Connan]

8 hours ago, offshorebirder said:

 

Or pull out your sand ladders!

 

Very few people carry those nowadays. They have mostly been replaced by plastic "traction boards".

My opinion of "traction boards" is that, if you can get out by just using them, you weren't really stuck at all. In sand specifically, I much prefer a jack, a spade and something to depress the tire's valve.

 

Good strong old-fashioned sand ladders are far more useful, but not normally in sand, rather as short "bridges", usually in rocky terrain. Some guys I have travelled with carry a short piece of scaffold plank.

But the types of terrain we are talking about are well outside the scope of what a self-drive tourist visiting safari destinations are likely to encounter.

[Peter Connan]

A relatively simple but potentially disastrous obstacle one might encounter is a water (river) crossing.

Water in the air intake will kill any internal combustion engine. Obviously when travelling alone this is rather a disaster.

The most common advice is to walk it first, but keep in mind that in the remoter parts of Africa crocodiles are an ever-present danger.

So start by asking whatever locals you come across. In busier areas, it might pay one to wait for an hour or so to see if another vehicle comes along. If one does, pay careful attention of where they drive through. And while waiting, keep a wary eye out for crocs, hippos and land-based predators, in case you do end up needing to walk it.

 

If you do walk it, and your underwear gets wet, then it's too deep. If you have trouble staying upright, then the flow is dangerously strong and there is a chance your vehicle may be swept away. Also pay close attention to how firm or sloppy the base is, and whether the exit looks doable. Walk where both wheels will be to make sure there aren't any holes, large rocks or logs.

 

When driving through, keep your windows at least partially open and leave your seatbelt off, in case you need to leave the vehicle in a hurry.

 

Next up, let's tackle some mud.

 

The problem with mud though is that there are so many different types of the stuff!

 

However, in essence there are two primary options (with lots of shade in between). Some mud is very deep. Sometimes there may even be a dry hard-looking crust on top hiding a near-bottomless pit underneath (typically salt pans or any other old lake-bed). Be very careful here. If at all possible, rather skirt around such sections. They can literally swallow vehicles completely. If you have to cross them, deflate your tires as for sand, and try hard not to apply any sudden loads, but do keep some momentum up to carry you over any particularly soft spots.

 

The other extreme is a layer of very slippery mud over a hard base. In this stuff you typically want your tires harder (say around 1.8 Bar), and the problem is running out of traction. This is one of the very few instances off-road where spinning the wheels might actually help, especially if you have tires with a fairly aggressive tread pattern. Higher wheel speed will flick the mud off the tires and clear the track.

 

In some areas (especially in Botswana and Zambia) one might come across long sections of flooded track at certain times of the year. These have aspects of both mud and water crossings. Once again, look at tracks and if possible follow others. 

 

When standing water or mud is visible on two-track dirt roads, it might seem like a good idea to take a detour. Be extremely careful of doing this! These two-track roads are almost always packed much harder by the passing of vehicles than the ground around it, and very often deviating from the tracks by even half a foot can lead to your vehicle sinking down to the belly. Only deviate from the tracks if the ruts are definitely so deep that your vehicle will belly out.

Edited April 22 by Peter Connan

[Peter Connan]

Lastly, uneven ground and rocky terrain.

 

Under these conditions you may have the following problems:

1) Running out of clearance. This could happen at the extremities of the car (often the rear bumper), or under the car.

2) Exceeding the vehicle's roll-over angle.

3) Lack of traction due to limited suspension movement.

4) Terrain moving under the vehicle.

5) Tire damage (specifically side-wall damage).

 

Firstly, if you think there is a chance of number 1 occurring, pay careful attention to how you approach the obstacle. Often, just adjusting this (called the line by off-road drivers) can prevent problems. If possible, get out of the vehicle and walk through the obstacle. Also if possible, get your passenger to "spot" you.

If the problem is under the car, try to keep your wheels on the highest spots. This may cause problem 3, but there is probably an easy fix.

 

Situation number 2 is obviously a big problem. However, it is fairly unlikely. Typical 4x4's have a roll-over angle exceeding 40 degrees. Most people get really scared at about 25-30 degrees. The exception is truck-based campers. These have much lower rollover angles and one should be really careful with them. Another factor is incorrect packing practices. Try to keep the heavy objects down low and put only light objects on the roof rack as far as possible.

 

Regarding situation number 3:

When a vehicle is on uneven ground, the opposite wheels on the higher spots will be carrying more than half the weight of the vehicle, and the other two wheels will be doing less than their share of the carrying. Traction is directly related to the force pushing the wheel down onto the ground. Thus, the wheels in the low spots can start spinning and losing traction. Often the driver's response is to apply more power, but this is usually not an effective strategy. In most situations, this will cause the wheel to dig deeper, making the situation worse. There are six possible cures, but to know which one you will need to use you will need to know what technology is built into your vehicle. The first and easiest is to rely on traction control. This is fitted to most of the latest vehicles, and all the driver needs to do is to not fool the system by doing anything sudden. IE, keep the throttle position the same for a couple of seconds. But if the vehicle is not fitted with traction control, this approach will make the situation worse. The second is to engage an axle differential lock. Most current 4x4's are fitted with one in the rear axle (automatic in some vehicles), and some common safari rental vehicles have two, one in each axle (primarily the current 70-series Land Cruisers and some Jeep models). Again, it is important to understand the operation of the vehicle, as these devices will only turn on if certain other conditions are met, and using them incorrectly can cause vehicle damage. Typically with the more modern vehicles, the drivetrain will need to be in 4wd and low range, and the vehicle needs to be stationary, possibly with the clutch depressed or the gearbox in Neutral or Park for automatic vehicles. Engaging an axle locker while a wheel is spinning can destroy the axle. But once the locker is engaged, the vehicle will often drive off the obstacle with surprising ease.

 

Failing the above two options, one can either choose a different line, or fill the holes (usually with rocks but possibly with traction boards or earth-filled sandbags) or winch or pull the vehicle off the obstacle. Lastly one can employ momentum. However using momentum does also carry risk to the vehicle and should be done circumspectly. The mantra "as slow as possible, as fast as necessary" is often taught.

 

Situation number 4 can be either large rocks moving in low-speed technical situations which are hopefully outside the scope of this piece, or shale or smaller rocks on a steep incline. In this situation, use axle differential locks if you have them. Other than that, momentum is the only useful tool. But once again, be careful. 

 

Sidewall damage is best prevented by being very careful to spot dangerous rocks or sticks and avoiding them.

 

Under all the above conditions, try first to go as slow as the vehicle can possibly go, but smoothly. On a manual vehicle, once in the obstacle keep the clutch engaged and the engine running at an idle. If this doesn't work, consider your options. Be careful of wheel placement. A capable driver spotting and directing from outside the vehicle is a great help.