Although most dirt roads are heavenly pretty and nice to be on for a holiday, dirt road driving could be a considerable hazard to people like us who drives on tar roads 90% of the time. The reason is that dirt is a loose and uneven surface that we are not used to and most of us do not drive enough of it regularly to pick up the skill and keep it honed. Safety first! It is not nice to have a well earned holiday ruined with an accident and the possible injuries or death that goes with it.
Poor Grip, Poor Surface
Most drivers who are a little bit aware of how poor grip affects a vehicle, knows that on a rainy day on tar stopping distances for one, increase considerably. In fact, it more than doubles at any speed. On dry dirt roads the grip is at best that of a wet tar toad.
Next, is an uneven surface. Even in a sedan with considerably better handling than a 4x4, negotiating a bend with uneven surface will unsettle a car at speed. On dirt roads, where corrugations are almost the norm in a corner, the effect is magnitudes worse.
With that, dirt roads have the additional entertainment of gravel that lies between the clean vehicle tracks and the size and shape of the gravel can be anything from fine pebbles to bigger round or crusted chunks. Crossing these islands will make your vehicle behave funny every time. Throw in some rain and mud and you have your entire mental capacity dedicated to keep it straight.
Thus, gravel roads are tricky because the conditions change never ending all the way from A to B.
Ensure Even Tyre Pressures
Before you leave, make 100% sure that your tyre pressures are equal. Rear tyres could be harder than front tyres to compensate for heavy load, but the important thing is that the two tyres on the same axle should have the exact same pressure.
To improve grip on dirt surfaces, it is recommended to drop tyre pressures to between 1.6 and 2.0 Bar. I usually drive at 1.6 Bar front and 2.0 Bar at the rear if I carry load, otherwise it is 1.6 Bar as the rear as well.
Uneven tyre pressure can have a profound effect especially on something like the Land Rover Discovery with a short wheel base.
One day, I was driving with my kids on a dirt road and the tail snapped out right with even shallow dips in the road.
I was mystified and the Disco kept me hard at work to keep it straight until I realised I did not check tyre pressures before I left. Be that as it may, the one wheel in front was almost 0.8 Bart harder than the other and with that adjusted, the difference was phenomenal.
Please check, it is a simple thing with a major effect on safety.
As soon as you leave the tar, the very first thing you need to do is to select 4x4 high range. If you drive a Land Rover with permanent 4x4, engage the centre diff lock (CDL).
However, please do not fool yourself and believe the camp fire stories that selecting 4x4 or engaging the CDL, makes the vehicle run on rails and that you are now invincible. It is not a magic lever that improves grip 10 times!
It does make a worthwhile difference though so use it to improve safety, NOT to go faster.
Keep it Slow
For my dad who drove on dirt roads and only dirt roads from as soon as he could see over the dashboard and then after that for the next 13 years of his life, dirt roads are easy and he can drive them fast. The farm boys grew up with it, they are used to the normal sliding of the vehicle and they can handle it like us manoeuvring into the tight parking spaces of shopping malls.
For the rest of us to keep rubber side down on a dirt road, there is one golden rule that stands out: Take it slow. Slow on the straights, much slower in the bends and slow when crossing those dreaded gravel islands.
With a fully laden 4x4 vehicle, stopping distances on dirt roads are very long and there is no way to quickly chop of some speed if something gets in your way.
I would recommend nothing more than 80 km/h irrespective of how temptingly good the surface may feel. I had the tail come out on a perfectly straight and supposedly even dirt road surface in my Passat once. It was strange and unexpected but I managed to catch it. It was a dire warning though.
Keeping it slow in bends are even more important. Dirt road bends often have corrugations through them because that is where drivers apply the brakes. This corrugated surface makes the wheels of the vehicle ride on the tips if you go too fast and grip is therefore minimal. This is then where the tail snaps out and if you have the added disadvantage of a trailer behind, your trouble is almost guaranteed.
Did I say go slow before? Do it. Try not to get into trouble in bends as things happen really fast there. The description that follows is not intended to make you any expert when things go wrong, hence the humoristic approach, but it may save your skin.
So, lets assume that you took great care to go slow all the way, but you honestly misjudged the next bend a little - it can happen often if you are inexperienced - and you try to bleed off some speed. Unkindly, you will find that the brakes locks up with frighteningly little pressure.
This is dangerous situation to handle but you need to deal with it. The best way is to let the wheels lock for as long as you can - which usually is only a second long if you are lucky - and GENTLY turn the steering in the direction of the bent. If I mean gently, it is about 1/8th of a turn only - nothing more than what you would usually turn in to get through the bend in a normal way. At 1/4 turn you have probably gone too far.
Do note that while your tyres are locked the vehicle will NOT respond to your steering input - do not try to steer more. The moment that you release the brake, the vehicle should immediately change direction and you will go around the corner much quicker than you like, but at least you will make it. If it does not happen, you are way too fast and your options are running out very quickly. Braking again will be of little help, but you may hit the tree a little slower.
The only thing that you can do now to change direction is to accelerate and hope that the front wheels will start to grip and pull you through. At this time, you may try a bit more steering too. That is why selecting 4x4 is so important. If you have a diesel with little power, apply all you have. In a petrol with plenty of power, you could overdo it so be careful.
If the vehicle does manage to change direction, you are still not saved as the tail may step out and you have to catch that too. So, you want to go left, but the tail wants to go right. Do know that the will of the tail will always prevails and you will have to oblige by steering in the direction the tails wants to go. Once gain, GENTLY but be quick. If that does not work, you will be lucky to escape with brown pants and a not to seriously damaged vehicle.
Needless to say, with a trailer behind the situation is so much worse and unpredictable. Take care. Don't get there.
If I forgot, keep it slow. When on a straight gravel roads, it is best to drive right in the middle of the road with you wheels in the clean spoor. If you stick to your side of the road, the vehicle tends to move left because of the curb of the road and that is dangerous and taxing on the concentration. However, when another vehicle comes from the front, you have to get to your side of the road. Reduce speed early and considerably, move over the gravel island at a shallow angle to your side of the road and if you are not feeling in full control passing the car form the front, just stop dead. It is no shame to be careful and get your family there without scratches.
Low Water Bridges
Keep it slow. As silly as it may sound, low water bridges are hazards that should deserve healthy respect.
The simple change of surface from dirt to cement and back to dirt combined with the quick down and up slopes, is an ideal recipe to seriously unbalance a vehicle.
Once again, slow down considerably. 60 km/h is way to fast to cross over a low water bridge.
Down Steep Passes
Keep it slow. Wow, you haven't seen that one coming! Long steep passes can make brakes overheat on the way down.
You have low range, now is the time to use it - unless you have an automatic gear box where engine braking often has no effect.
Select a gear that allows the engine to provide all the braking you need and allow you to wind through the slow corners without you touching the brakes. Be patient on the straight pieces and do not try to make up time between bends.
If you drive an automatic vehicle, you need to be very aware and act at the very first sign of brake fade. Stop immediately and let the brakes cool off for a few minutes before you continue.
One other important thing to remember: The guy who comes up the dirt road pass, ALWAYS have right of way. When ever possible try to see if you can spot any vehicle coming up and make sure you pull off at the first possible place. On thin roads there may not be another convenient spot and it can leave you and the other driver with no options and obvious danger.