wildcat

5 reasons to not use SUV's for off-road In my previous advice I have explained: How to choose a capable off-road car? based on low range, ABS and Diff-locks. In this advice I will explain why SUV’s and crossovers do not make good, capable off road vehicles. The SUV’s / crossovers have serious design flaws (or differences) that make them unsuitable as off road vehicles. Below are the 5 points that will make this class of vehicle unsuitable as off road vehicles. 1) SUV’s have poor suspension articulation Main part of the reason why proper off road vehicles can do what they do is the fact that they have a long suspension travel, otherwise known as “suspension articulation”. What this means in the real world is that these vehicles can cope with uneven terrain because the suspension systems allow the wheels to move for up to 40 inches (1 meter) and more with respect to each other. This means that even on extremely uneven terrain, all the wheels can remain on the ground, thus maximizing the traction. In the case of SUV’s and crossovers, the maximum suspension travel is about 9-10 inches (seldom more), which means that once a wheel has moved as far as the suspension allows it to travel, the part of the vehicle lifts off the ground. When this happens, one or more wheels lose traction and if the vehicle is not fitted with diff locks, the vehicle is stuck, and has to be towed out of the obstacle, or uneven terrain. 2) SUV’s are not flexible enough Proper off road vehicles that have separate, “stepladder” chassis are extremely flexible, which also helps to keep all the wheels on the ground. In combination with their long, built-in suspension travel, this means that a proper off road vehicle can negotiate types of uneven terrain that no SUV or crossover ever can, simply because SUV’s cannot “bend” enough to allow the wheels to remain on the ground. 3) SUV’s do not have enough ground clearance While some SUV’s have about the same ground clearance as many proper off road vehicles, the problem is that their suspension setups do not allow for heavy loads. This load is sometimes made up of up to seven passengers, but in most cases, the load comes from the suspension being too soft. When an SUV goes over, say, a bump, the vehicle drops down too low when the suspension compresses as the vehicle leaves the obstacle, and especially so when the vehicle is travelling too fast. Since the suspension compresses too much, the vehicle’s ground clearance can be reduced to the point where some components like differentials, cross members, and even the engine and transmission can hit obstacles like rocks. Proper off road vehicles do not have this problem, because their hard suspensions do not compress to the point where ground clearance is affected in meaningful ways. Moreover, because proper off-road vehicles have hard suspensions, its ground clearance actually increases when one or more wheels go over an obstacle, since the vehicle’s weight is always fully supported by the firm suspension(s). This is not always the case with SUV’s, since their suspensions were designed to move in such a way that uneven spots are absorbed without excessive body roll or movements. Thus, the vehicle is not lifted off the ground when one or more wheels pass over an obstacle, and if the vehicle is loaded with passengers, it could happen that even small obstacles could hit one or more critical components. 4) SUV’s are overly complicated The ideal off road vehicle has as few components as possible to make it work, with driver and passenger comfort coming a long way behind requirements like reliability, ease of use, and easy repair ability. This is not the case with luxury SUV’s and crossovers that are designed to give the driver and his passengers the most comfortable ride possible on hard, paved roads. While we agree that some SUV’s are able to complete short and easy level 1 off road trails that are designed with SUV’s in mind successfully, the problem is that SUV”s are too complex (complicated) to do anything else reliably. Part of the problem is that the electrical systems of modern SUV’s are not designed to cope with the heat, dust, and vibration that go with serious off road driving. In many cases, the air suspensions of these vehicles are protected by dozens of fuses, relays, and control units that were simply not designed to cope with the demands of off road driving conditions. No vehicle that can be completely disabled when a single fuse blows (such as when the compressor stops working when its fuse blows) can ever be trusted on a long, difficult off road trail, and especially a trail that requires extreme care by an expert driver. 5) SUV’s do not have recovery points It is one thing to clown around on some loose sand, or to drive an easy, level 1 trail when there are plenty of other vehicles around to supply a tow, but it is something else entirely when that vehicle has to be recovered in very difficult terrain. For instance, a vehicle that is stuck in sand up to the depth of the tyre sidewalls, can require a force of up to three times the force required to move it if it were on a hard surface. This force is calculated by using the weight of the vehicle as a base line; therefore if your vehicle weighs say, 1800 kgs, you will need a force that is equal to the vehicle’s weight, plus ten percent of that value to move it on a hard surface. In this instance, you will need a pulling force of at least 1980 kg. However, if as we said, the vehicle is stuck in sand up to its rims, you need at least three times that pulling force, thus, 5940 kg, and that is where the problem comes in. Even if there is a vehicle with a winch available, there is no attachment point on the stuck vehicle that is strong enough to withstand this pulling force, and it is almost certain that the normal towing point or recovery eyelets will tear out from the vehicle- leaving the vehicle stuck in the sand, and probably hurting someone as the winch cable snaps and recoils. Depending on circumstances and local conditions, the required pulling force can be as high as six or even seven times the value of the baseline figure, which should make it obvious that unless the vehicle has properly rated recovery points, it should not be used off road, and most certainly not in conditions where it might have to be towed out with forces that exceed its weight by several times. SUV’s are simply not designed to withstand pulling forces of this type, and any attempt to subject a vehicle to these forces is irresponsible, dangerous, and likely to hurt someone. So, no, SUV’s and crossovers do NOT make good off road vehicles, even if it is only because they cannot always be recovered safely.

How to choose a capable off-road car? Off-road driving means different things to different people, and one of the most common, and potentially most expensive mistakes made by novice drivers is to think that SUV’s and Crossovers are off-road vehicles simply because they have some AWD capability or they look very similar in height and width. A current post on this forum is good case in point, since it asks if a Renault Duster is a capable off-road vehicle. The answer is simple; No, it is NOT a capable off road vehicle, and no serious off-road driver will ever see it, and other soft-roaders like it as a capable off-road vehicle. This article is not intended to bash Renault Dusters and other vehicles like it; it is intended to explain why they do not make a capable off-road vehicles. For the purpose of comparison, I will stick to why Renault Duster is not a capable as an off-roader, although the reasons listed here apply to all SUV’s and crossovers from almost all the brands and regions. It should have a low range Having a low range is of critical importance in any capable off-road vehicle. It may be true that a Duster has a specially geared first gear that provides a bit more torque to the driving wheels, but the gearing is not low enough to prevent wheel spin, which is an absolute requirement for driving in desert sand. A proper low range should reduce the gear ratio in first gear to the point where the maximum attainable road speed in first gear does not go over 8 - 10 km/h. The advantages of this should be obvious - the low gearing prevents the wheels from rotating fast enough to start wheel-spinning in sand or mud, so with suitable tyres, all of the rotation of the wheels is converted into traction. Soft-roaders like SUV’s do not have low enough gearing to prevent wheel spin, which is why they get stuck so easily. It should have way to disable ABS brakes ABS brakes can be dangerous in off road driving, since it increases stopping distances. This might sound strange, but the fact is that ABS was designed to work on paved roads, where traction is a lot higher than on even the best off road surfaces. On tarmac, the ABS allows the brakes to work at maximum efficiency because there is enough traction to slow the vehicle down effectively without skidding on any direction. However, in the off-road environment, and especially with tyres that are designed for on-road use, traction is reduced to only a very small fraction of what is available on a paved road. Thus, when a driver applies ABS brake when driving on loose surfaces, the wheels lock almost immediately, and before the vehicle has started to slow down. Moreover, as soon as the wheels lock, the ABS system releases the brakes until the wheels lock again, and so on and so forth. In practice, this means that the vehicle effectively has no brakes, and the vehicle could easily drive over a cliff because it cannot stop in time. Any capable off-road vehicle should not have ABS, or if it has, it must have a means to disable the ABS when it is not being driven on hard, paved roads. The most effective way to stop a vehicle on loose surfaces is to allow the wheels to lock, which causes them to dig into the ground, thereby creating increased rolling resistance, which is what stops a vehicle on any surface. It should have a proper diff locks The only differential locks that work reliably are those that lock mechanically. Almost all soft-roaders with some AWD capability have various kinds of viscous couplings that lock only the transfer case to supply torque to the diff that does not normally drive the vehicle. The problem with this is that viscous couplings can seldom handle high torque values over long periods on the one hand, and that the actual differentials on the driving axles are sometimes not locked. Although the Duster can be retrofitted with a rear differential that locks mechanically, there is no point in locking only the front differential in tricky or difficult driving conditions. With proper diff locks, all the wheels receive the same amount of torque but with soft-roaders, and especially those that do not have a low range, the torque that is supplied to the wheels is delivered at wheel rotation speeds that is too high for the tyres and suspension to maintain traction in deep sand or mud. Moreover, soft-roaders are often fitted with traction control systems that are based on the ABS brakes, which means that the system’s stored energy can run out before the vehicle is out of a sand or mud trap. If this happens, the automatic diff-lock control system cannot control wheel spin on an axle, which in turn means that the driver can lose traction on two or more wheels until the traction control system is recharged. On a proper off-road vehicle with mechanically locked diffs, torque is supplied to all wheels equally all of the time, and since momentum is the off-road driver’s best friend, there are no interruptions in power delivery that can cause the vehicle to sink into soft sand or mud. No diff- lock system that works with viscous couplings, and/or that depends on a brake-based traction control system can ever be effective in deep sand or mud, since it cannot supply torque to all four wheels for long period of time. Read more: 5 reasons to not use SUV's for off-road