Overland glossary: the words of the desert and the 4x4

Traveling over land, across long distances, with your own vehicle — 4x4, motorcycle, van, truck — where the journey itself, not the destination, is the point. You are self-sufficient for days, you sleep wherever you arrive, you cross countries and borders. And the fundamental difference from the pure off-roader is all in the attitude: the off-roader seeks out problems and difficulty, as a challenge; the overlander tries to avoid them, for survival. Obstacles are tackled only when they can't be gone around — to reach the goal, not for the show.

The "sand sea": an expanse of wind-shaped dunes — the postcard desert. The ergs overlanders visit most: Erg Chebbi and Chigaga (Morocco), the Grand Erg Oriental (Tunisia/Algeria). It's the most technical environment for a 4x4 — asymmetric "one-way" dunes, sand that changes with the time of day — and it's the place where a local guide truly makes the difference.

The stone desert: bare rocky plateaus where the wind has carried the sand away, leaving rock and rubble. For the driver it means hard, sharp ground: tires at near-road pressure and attention to the sidewalls — this is where rocks cut the shoulders of deflated tires. The classic example is the Hammada du Draa, in Morocco.

The gravel desert: flat, endless plains of pebbles and compacted sand. It's the easiest and fastest desert to drive — and deceptive for that very reason: distances look short and aren't, and fesh-fesh can hide in the depressions. "Reg" is used in the western Sahara, "serir" in Libya and Egypt.

The most feared sand of all: powder as fine as talc, often pale, that forms on clay-based tracks with the passage of vehicles. It looks like solid ground — then you sink into it. It throws up clouds that erase visibility and gets in everywhere, air filters included. You tackle it with momentum, steady throttle and low pressures: never stop in the middle. In African rally jargon it's the word that makes everyone's antennas go up.

The unpaved road of the desert and of Africa: born from the repeated passage of vehicles, not from a blueprint. It can be fast, supportive gravel or a broken-up hell — and the same piste changes face with the seasons, the rains and the truck traffic. You learn to "read" it: several parallel tracks mean everyone is avoiding something (holes, corrugations); fresh tracks tell you who passed and when. On the piste, distances are measured in hours, not kilometres.

The "corrugated iron": kilometres of small, hard, regular waves carved into the surface by passing vehicles. The car judders violently — and the solution is counterintuitive: you accelerate, up to the speed where the car "floats" across the crests and the vibration stops. Careful though: at that moment steering and brakes respond far worse than normal. You'll find the full technique in the sand driving guide.

The salt lakes of the Sahara: flat, dazzling expanses with a salt crust that looks solid — and mud underneath. The most famous is the Chott el Jerid, in Tunisia. Off the marked crossings the crust can give way, and there a vehicle sinks to the chassis: one of the hardest recoveries in the desert. You cross them only on the beaten paths, and never after rain. A "chott" is the large seasonal salt lake; a "sebkha" the salt flat.

The bed of a dry river. It's often a natural travel corridor — firm ground, vegetation, sometimes wells — but it's also a danger with two faces: patches of soft sand, and above all flash floods, which arrive from rain that fell kilometres away. The rule that isn't up for discussion: you never camp in an oued.

The second set of gears of true off-roaders: a reduction gearbox that multiplies torque and lowers all the speeds. In low range the engine works in its best rev band even at walking pace, and control becomes surgical. You use it on sand (typically second or third low), steep climbs and descents, technical terrain, towing and recoveries.

For the same final ratio, on a manual gearbox using a higher gear with low range engaged can put less stress on the main gearbox, distributing the reduction between gearbox and transfer case. There's also an important practical difference: driving in first high, if the situation worsens and you need a shorter ratio, you have to stop — or slow right down — to engage the reducer; travelling in second or third low instead, you already have one or two shorter gears immediately available.

On an automatic, the advantage of low range mostly concerns the torque converter: in high gears, at low speed and under heavy load, slippage generates heat; low range lets you work with more favourable ratios, less slippage and less thermal stress on the fluid and the transmission.

And one advantage you feel immediately: starting off on difficult terrain, deep sand or a steep slope, low range strains the clutch far less — the torque multiplication does the work you would otherwise burn into the clutch.

The differential lets the wheels turn at different speeds — indispensable when cornering on tarmac. But off-road it has one flaw: it sends the drive to the wheel with less grip. Hence the short rule to remember: with all differentials open, one wheel losing grip is enough to stop you. The lock eliminates the differential: the wheels turn together, by force.

The three locks are used in escalation:

Why is the front lock the last resort? First: with the front lock engaged the car practically doesn't steer — you turn the wheel and it carries on almost straight. Second (and this goes for the rear too): a locked axle is under far greater stress — with the wheels bound together it's much easier to break joints and half-shafts, and if you overdo the throttle, breakage is guaranteed. On top of that, the front drivetrain of almost every off-roader is lighter than the rear in dimensions and tolerances: a locked front axle is the one most at risk of all.

And always: locked on loose ground, unlocked where there's grip — a locked differential on tarmac, in a curve, winds the transmission up to breaking point.

The two philosophies of four-wheel drive. Full-time (Land Rover style): all four wheels are always driven, with a centre differential — lockable — that allows use on tarmac too. Part-time (Land Cruiser 70 Series style): normally rear-wheel drive, 4WD engages on command and there is no centre differential — which is why on tarmac and grippy surfaces you travel in 2WD, or the transmission winds up. For sand, both work perfectly well: what matters, as ever, is that the mechanicals are simple and robust.

The raised air intake at roof level. Contrary to the myth, in the desert it's more about dust than river crossings: it feeds the filter cleaner, cooler air, and the filter clogs more slowly. Does it help? Yes. Is it essential? No — especially if the vehicle has a big filter, like traditional off-roaders. And it must be fitted properly, or it does more harm than good. If you fit one, add a cyclonic head: the round spinner on top that expels sand by centrifugal effect — but it must be sized for your engine: too little flow and you lose performance, and with turbos you risk abnormal oil consumption.

The mechanical crossroads that transmits drive between shafts working at an angle: a steel cross on needle bearings, fitted at the ends of the propshafts. On African pistes it's one of the parts that suffers most: vibration, dust and load wear it down. It needs fresh grease before departure (where there's a grease nipple) and listening to during the trip: a "clack" when engaging gear, or a vibration that grows with speed, are its ways of warning you — before leaving you on foot.

The two families of off-road tires. AT (All-Terrain): the compromise — moderate tread, good on tarmac and piste, quiet. And on snow they do far better than MTs. MT (Mud-Terrain): deep, widely-spaced lugs and a tough carcass. Their advantage in mud is structural: the spaced-out lugs mean the tire self-cleans with every revolution — something the AT can't do. But mind their limits: on wet tarmac, with MTs, the car practically never stops — you need caution and double the distances — and on tarmac in general they're noisy. On sand they're a touch too aggressive: they dig more, and the throttle needs metering even more finely.

That said, the overland travel tire is almost unanimously the MT: it's highly puncture-resistant and there is no situation that "stops you". With an AT, one muddy stretch is enough to stop you; with MTs it's much harder.

When the tire comes off the rim: the bead (the sealing edge) slips off and the wheel deflates instantly. It happens at low pressure, almost always on the front axle with the wheels turned: the weight of the car pushes sideways and peels the bead off the rim. The classic scenario: coming down a steep dune and immediately steering hard — done. The risk grows with a heavily loaded vehicle, and even standing still: heavily deflated tires left out all night in the cold can de-bead without moving. Prevention: come down with the wheels straight, one extra manoeuvre at low speed, fronts slightly harder. Reseating a bead in the field can be done — ratchet strap around the tread and a compressor — but it's a serious chore: better not to get there.

The elastic recovery rope: under load it stretches, stores energy and releases it progressively — no violent jolts, which is exactly what sand recoveries need. It's the best tool for recoveries between two vehicles. It attaches only to the chassis recovery points, with shackles. And one absolute rule, kinetic or not: never do a towed recovery in reverse — differentials explode.

The wide construction-site slings that almost everyone uses instead of the (expensive) kinetic rope — and they work. They carry a standard label with the load rating and, in Europe, a colour code (EN 1492-1): for a 4x4 the yellow ones do fine — 3-tonne nominal rating with a 7:1 safety factor, breaking load around 21 t. Their limit: they are not elastic at all — pull gently, and if it doesn't work, try again. Longer is better: 2 metres is too little for any run-up and keeps the cars too close. Buy them at the DIY store at a reasonable price, or at the 4x4 shop at an excessive one: same product, different label.

The U-shaped link with a screw pin that connects straps and recovery points. You need at least two, big ones — thumb-thickness is about right. Check before departure that they actually fit your anchor points. The expert's trick: after seating the pin, back it off half a turn — that way, in the deformation under load, the thread won't seize. There are also soft shackles (textile): lighter and quicker to use. Recoveries are done with shackles only: no knots (a knot that has survived a pull turns to steel: you'll never untie it) and no improvised anchors.

The drum winch on the bumper: the safest recovery system there is — slow, constant, inexorable. Its limit in the desert is a different one: it needs something to anchor to, and in the sand there's often nothing — except another car. On choosing one, some honest advice: for non-continuous use even budget winches are perfectly fine, as long as the rating suits your vehicle — for an overlanding rig, stay above 12,000 lbs. What changes with the prestigious brands, besides the price, is durability and recovery speed: things that don't matter much for occasional use. The same safety rule as straps applies: during the pull, never stand on the line of the cable — if something gives, it flies like a projectile along that direction.

The only points on the vehicle designed for the load of a recovery: strong, and bolted to the frame rails. The tow hitch and the tie-down eyes are not: anything that isn't a recovery point breaks, bends or flies off like a projectile — shattered windows and radiators, if you're lucky. If your car doesn't have them, it's probably not an off-roader suited to sand; they can be added aftermarket, but installed properly.

The standard file format for GPS routes: a sequence of points any navigation app can read. In the desert it's your Ariadne's thread: download the track and offline maps before leaving (there's no signal out there), and if possible the satellite imagery too — seeing the shape of the dunes from above helps a lot. And it holds on organised tours too: it's always better to know where you are and where you're going, even when you have a guide.