There are two basic types of axle systems – independent and solid axles. Each have merits, and each have their drawbacks. Discussions as to which is better often lead to argumentative stalemates, so I will try to present an objective description of both. Note that many modern off-roaders and leisure 4×4’s employ a combination of the two – solid axles at rear, and independent at front.

Solid Axle Suspension

Solid axles (referred to by some as solid beam or live axle) mean suspension systems where the wheels are joined to an axle which consists of a solid beam. This has some interesting effects when driving both on- and off-road. For the sake of this discussion we’ll limit ourselves to the front wheels only, although it obviously applies to both the front and rear axle. When driving a vehicle equipped with solid axles on the highway, and an irregularity or bump is encountered with, say, the left wheel, that wheel will lift to go over the bump. Because the axle between left and right wheels is solid, the entire front of the vehicle will also lift up. The result is that solid axles make for a very irregular, and consequently “hard” ride on the highway.

Off-road, however, the same effect can be magnified, due possibly to larger bumps, in our hypothetical case the ubiquitous rock. When the front left wheel encounters a rock, and the front right wheel continues on even ground, the front left wheel will rise, raising the differential and the body of the vehicle with it. This has the desired effect of raising the differential out of harm’s way.

Another interesting effect of solid axles is that when the front left encounters a rock, and the front right falls into a hole or depression, a solid axle vehicle is less likely to loose contact with the ground. This is because the solid axle and vehicle weight force or “push” the front right down, more often than not maintaining contact with the ground, and subsequently maintaining traction on both wheels. The obvious benefit here is off-roading (such as rock crawling), whereas high-speed, on-road driving can be bone-jarring.

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