Nowadays, a lot of cars call themselves 4x4s. It is important before you go rallying in the desert to distinguish what is a “real” 4×4 from a SUV which can also function in 4 wheel drive, meaning that the power of the engine is distributed to all 4 wheels at the same time.
This is what Alain from Baroud Terre du Sud in Marrakech has to say : First of all, a proper all terrain vehicle must be extremely solid as it will be driven on difficult terrain. A 4×4 must be high enough in order to go relatively easily over rough terrain , which means that beyond having a high car body, it must have good attack angles to go up slopes and good outgoing angles in order not to drag the car bottom on the ground.
It must also have the compulsory differential locking in order to allow wheels on the same axle to work independently, something that is necessary when your wheels are bogged down (in sand or mud); also to overcome forces generated by the weight of the vehicle (rolling resistance), steep grades (gravity) and resistances created by material pushed by the tires (sand, mud, etc)– best combined under “Load”, the vehicle needs to generate sufficient torque by combining engine torque and adequate gear sets.
In order to generate torque, a counter force is needed: Traction. A proper 4×4 will provide a lot of traction to make the vehicle move in difficult terrain.
And last but not least, a powerful engine will be of great use enabling the driver to move forward softly in low rpm without having to press the accelerator to its max, something rather dangerous when you suddenly find yourself past the difficult zone.