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4 Wheel Off Road Desert Truck Setups - Prerun Fun

Posted in Features on August 1, 2003
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Photographers: Ben Sudweeks

Let's be realistic for a second. How many of you don't like lots of power and going as fast as possible while hanging onto just a shred of control? Those three of you who raised your hands may now flip past these next couple of pages because this is what the desert is all about. The desert has been a popular getaway for speed freaks for years, with the limits of your suspension and power being about the only thing keeping you from reaching Mach 1 through the dusty terrain. So let's get into it. In not much time, you should have your truck running and ready for some prerunning.

By the way, we're sure a few of you are curious about the lead shot that was taken at Oceano (Pismo) Dunes last year by Ben Sudweeks. You can see the rest of the shots at www.atv-racing.com. The driver is Jordan Jones and his friend's truck was over 13 feet in the air. The truck took one year to rebuild, and he still has a bump on his head.

Body, Armor, & SafetyYou want the body of a desert truck to be as light as possible. That means removing anything you can that isn't necessary and replacing fenders, hoods, and in some cases, doorskins with fiberglass to reduce weight.

As for any type of vehicle protection, you want to stay minimal for weight purposes. There's not going to be much around you in the desert, but you should have some type of prerunner bumper in the front and rear.

Safety is a major concern and you'll want to protect yourself well just in case you're involved in a high-speed crash. A full interior cage should be adequate, but a fully-caged tube chassis is the best for protection (and strength). The interior should sport some supportive seats, and four- or five-point harnesses are almost a must. This way, you'll stay put in harsh road sections.

Engine, Tranny, & AxleThe engine on a desert truck should be able to put out a lot of horsepower and high rpm. A good starting point is 300 hp. The engine manufacturer is up to you, but make sure it's not a pig and that it is reliable!

An automatic transmission with a manual valvebody and shifter would be the most ideal for desert fun, but you can make due with a lesser-built tranny if funds are short. Since your momentum is carrying you over most objects, there are not the excessive loads put on your transmission or transfer case as in other off-roading arenas.

A manual tranny can be used, of course, but you're going to have more fun and a smoother ride with an auto.

Gearing should be matched to the tires for similar ratios to a stock setup. You're going to be going fast, not crawling. A lightweight axle like a Ford 9-inch is a great choice for a cross between strength and weight. It rates as a 11/42-ton axle, but can be built stronger than a Dana 60. A Dana 60 would be a good choice too, but it is heavier than a 11/42-ton axle and has less ground clearance.

Tires, Wheels, & Pressure For desert running, you're not going to need a very aggressive tire. An all-terrain of some sort would be your best bet. For a more purpose-built tire you should look to something like a BFGoodrich Baja T/A or a Goodyear GSA. Both these tires are made for desert racing and have thick sidewalls that will better resist punctures at high speeds.

Depending on whether or not you have a fullsize truck, you'll want to go with tires ranging somewhere between 33 and 37 inches tall. You don't want to have tiny donuts that'll get sucked into holes and ruts, nor do you want huge diggers to lug around. You want to keep your unsprung weight (the weight below the vehicle's suspension) down so as not to break components or distort the suspension's intended ride.

Wheel choices are left open to you, the builder, but the sport has been moving aggressively towards 17-inch rims with bead locks. The bead locks will make sure your tire doesn't separate from your wheel when your tire takes on lateral force.

Pressure should be kept at around 15 pounds or more. You do not want to have too low a pressure because of the higher speeds you will be reaching compared to other forms of off-roading. Bead locks will allow you to go to lower pressures than a wheel without bead locks.

Suspension & ShocksThis is what makes a desert truck a desert truck. You can have all the power you want and the best drivetrain and tire combo possible, but you ain't gettin' over 40 mph without a supple suspension. Obviously an IFS or Ford twin-traction beam (TTB) setup is going to give a better high-speed ride than a solid front axle if you're talking stock suspension versus stock suspension. The TTB Ford has been known for years as a great, easily modifiable suspension that can provide you lots of travel, so this would be a great starting point or even great as a swapped-in unit. An IFS rig can make a great choice if you just want to bolt on a lift and go. Two-wheel-drive IFS trucks are tons of fun and make great jumping rigs. For a four-wheel-drive IFS truck, though, there are very few kits on the market right now that will add any travel to your suspension. Hopefully that will change someday soon, but in the meantime, you're limited to the amount of travel that you have in stock form. If you have $50,000 to drop on a custom IFS front end, then nothing is going to catch you in the whoop-de-doos. But if not, then it is much easier to work with a solid axle.

For those of you with a solid axle (which most all of us have in at least the rear), you can gain travel and achieve a better ride by tuning your suspension. If you're on a budget and have a leaf-sprung vehicle, keep the leaves. If you can't even afford to buy some prerunner leaf packs, you can tune your leaf pack to your liking by adding or removing a leaf or two from the pack. Your truck probably has an overload spring on it, so try taking that one out first.

If you have cash for a link-type setup or already are blessed with one such as those in the '94-and-up Dodge front ends or '99-to-current Tahoe, Yukon, Suburban, or Avalanche rear ends, you're loving it. You can either have coil springs or splurge for coilover shocks to keep your ride cushioned in harsh hits. The links that connect the axle will have to control vertical, lateral, forward, and backward movement.

All the preceeding suspensions will benefit greatly from using a remote reservoir shock as well. Remote reservoir shocks have extra fluid capacity that keeps heat dissipating much better than a single reservoir shock. The reason is this: When you are going fast and taking air, your shocks cycle up and down very fast, which heats up the oil in them quickly. When the shock's oil heats up, it can thin, foam, and make for inconsistent damping. A good rule is the more fluid capacity you have in your shocks, the longer your good ride will continue. The reservoir allows the shock body to stay full of oil and moves potential foaming to the reservoir. Plus it allows more shock travel for a given extended-length shock.

Experimental and the FutureThe future of this sport lies in IFS front suspensions that will give the travel needed without binding front drivelines. New types of joints will give the freedom needed for the suspension to travel. Tires will be getting a little bigger, with 39-inch competition tires coming to the scene. Motors will continue to produce more horsepower and there will be even greater evolutions in safety than ever before. The trucks will be lighter, faster, safer, and stronger, with the only limits being what we can physically withstand.

For link-type solid-axle suspensions you have two basic choices that have numerous but slight variations. The first choice would be a five-link system using four control arms to control forward/reverse and vertical movement. Two control arms are on the top of the axle, and two on the bottom. The fifth link is the Panhard rod, aka the track bar. It mounts parallel to the axlehousing (lengthwise) and controls the lateral movement. The second choice would be a triangular-arm setup. This type of design needs no track bar because the two upper links are angled in the shape of a triangle instead of being run parallel to each other. This upper triangle not only locates the axle vertically, but also prohibits lateral movement. The lower links in this design are kept close to parallel, the same as in the five-link setup.

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