While plenty of automotive enthusiasts are all about carving corners at the local track days, it’s a special breed that leaves tarmac behind for the dusty trail ahead. If your chosen ride is of the four-wheelin’ variety, here’s how you can modify it to dominate the dirt and mud.
Handling The Terrain
Building a good offroad rig requires a very different focus than building a car for street performance. A screaming high-performance engine is of no use when your tires are spinning in the air because you’re stuck in deep sand or on top of a pointy rock. Instead, four wheelers are concerned with a whole different set of parameters. Ground clearance is key to getting over obstacles without getting stuck, and good articulation is key to keeping your wheels on the ground and pushing you forward in deep ruts and on crazy angles. You’ll also want plenty of low-down torque, and tyres that can grip up in all conditions without snagging a puncture. It’s a whole different ballgame, so read on!
Wheels and Tyres
Tyres are the vehicle’s contact with the road, and without a good set of tyres, you’re going absolutely nowhere. Tyre choice for a four-wheel drive application is dependent on where you want to go, and what you want to do. Specialised tyres are available for sand driving, for example, and if you want to play in the mud, a good set of “mud boggers” will do you well. Of course, for those intending to split their time between the highway and the trail, a more conservative set of all-terrain tyres might be the best bet for a blend of off-road performance and on-road comfort.
Fitting bigger tyres is perhaps the most popular modification for offroad vehicles. They’re perhaps the easiest way to gain ground clearance and help a vehicle roll much more easily over small holes and obstacles on trails. However, their greater circumference can decrease vehicle acceleration, and the heavier unsprung weight can lead to handling and braking issues.
Wheel choice is also a major consideration when outfitting an offroader. Classically, 15″ wheels were the norm, but 17″ designs are now more common. Wheels in this size provide for plenty of sidewall, allowing the tyre to help soak up bumps off road. Choosing an oddball wheel size will give you no end of headaches trying to find tyres to match, so it’s best not to stray from the norm. Of course, if you’re getting super serious, particularly in rock crawling disciplines where very low tyre pressures are key, you might consider getting a set of bead lock wheels. These come with special retaining rings that hold the tyre to the rim mechanically, rather than simply relying on air pressure. These allow the tyres to remain on the rim at incredibly low air pressures, allowing for maximum grip thanks to the greater contact patch of a lower-inflated tyre. However, they add a lot of complexity and weight to a wheel, and can be illegal in some jurisdictions, so be wary.
Lift kits are another popular way to increase ground clearance of offroad vehicles. They come in two major variations – suspension lifts and body lifts, each with their own strengths and weaknesses. Suspension lifts consist of installing longer springs and higher travel shock absorbers, lifting the entire vehicle’s ride height. This generally offers the best improvement to articulation and ground clearance, however can be expensive due to the need for a full set of new suspension components. A body lift, on the other hand, consists of simply raising the body of the vehicle relative to the chassis. This is cheaper than a suspension lift, and is often done with a series of spacers between the frame and cabin of a vehicle. Commonly done to allow clearance to fit bigger tyres, a body lift does not increase ground clearance of the vehicle in and of itself. Often times, a combination of suspension and body lift will be done, providing more ground clearance and providing the most possible space for larger tyres, further raising the vehicle’s ride height.
Lifts of either kind can have major impacts on handling, due to the higher center of gravity of a lifted vehicle. Additionally, execution can be difficult, with many lifts requiring modifications to drive shaft angles, brake line routing, or even steering shafts. All these components are designed around a set factory ride height, and can only withstand limited adjustment before problems become apparent. Often, lift kits that go beyond a limited height range will come with equipment to help solve these problems during installation.
The open differential is a useful invention that allows a car’s wheels to turn at different speeds, such as when cornering. This allows for smooth driving in regular conditions. However, on loose surfaces, it can be more of a hindrance than a help. This is because an open differential transfers torque equally to both wheels. For example, when one wheel is in the air or spinning in mud, it will spin freely. The other wheel attached to the differential will get the same amount of torque as the wheel spinning in the air, which is virtually none. This can make forward progress difficult when one wheel leaves the ground or gets stuck in sand — conditions regularly encountered on any off-road trail.
The popular solution to this is the locking differential, commonly fitted to four-wheel drive vehicles that don’t have time to get stuck. Often available as a factory option, they can also be fitted as an aftermarket upgrade to most popular four-wheel drives and trucks. Available in air and electrically activated versions, when switched on, they lock both sides of the differential together, forcing them to spin at the same speed. This allows greater torque to be supplied to whichever wheel actually has traction, making for much better progress in mud, sand and snow. The trick is that they can be switched on and off, so once back on road, the vehicle can be driven without suffering all the drawbacks of a locked differential on a high-grip surface — like drivetrain damage and annoying tyre squeal around corners.
Locking differentials can be difficult to install for the novice, and may require the assistance of a dedicated diff shop to put together if upgrading a stock differential to locking operation. However, the gains they bring to performance can’t be understated, and they’re a necessity for any serious offroading in mud and sand. Save your pennies, because this hardware certainly doesn’t come cheap!
Having the right gear on hand can save you from getting stuck waiting for help on a distant trail. Basic tools are a must, as there’s plenty of hazards offroad that will catch out the unprepared. As a start, a full set of tyre changing gear, including a jack, is key, along with gasoline and water — potable for yourself, and some for the car’s cooling system in the case of overheating. A pair of recovery boards can help if you get bogged, along with a shovel for digging your way out of more serious jams.
Looking further, you may want to fit brush guards and bash bars to prevent damage to your vehicle from the more gnarly trails out there. These can often serve as great mounting points for additional gear like winches and lights, which can aid in recovery, or help you spot obstacles before you even get stuck in the first place. Having a stout towing point on your vehicle is also key, so you don’t rip a bumper off when a friendly Jeep stops by to pull you out. Of course, when wiring in accessories, make sure to use properly rated conductors and weather proof connectors, otherwise your adventures may be cut short by an electrical fire!
Offroading is a fun practice, and often times, a stock vehicle is more than enough to get started on basic trails. The key is to find out what area of offroading you like, and then modify your vehicle to suit as you gain more driving experience. Spending huge money on a maximum-articulation suspension lift is great for rock crawling, but probably not the first mod you’d make for snow racing, for example. Focus on figuring out what you’re into, and go from there!