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A Desert-Raid car, Inside & Out

How do our cars handle so well?
There are a number of factors that affect an off-road cars handling. an off-road car will never turn as tight and nice or be nearly as smooth as an on-road car, but an on-road car can't go 120 mph over the whoops, or jump 80 feet! The reason for all of this is in long travel suspension designs. In the off-road world, there are a few variables that do not exist in on-road driving; 1) roads may exist, but are generally not groomed and can have large rocks, whoops, jumps, or any other of a number of obstacles that do not exist on streets and highways. But, since these obstacles are what make our sport fun, we have designed suspensions capable of handling them without breaking (or not as often). 2) At any given point all four tires could leave the ground, on purpose or not, and you could be twenty feet in the air. When you return to the earth, the car needs to soak up the hit without giving you back and neck problems, and since you'll want to do it again, it needs to soak these hits up repeatedly, and smoothly.
There are many variations of front and rear end designs, so I'll just talk about ours, and why we decided this was the best way to go. I'll discuss the limitations and positive points, and give you a base of knowledge on how and why it works.

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Long Travel J Over A Arm Front Suspension

Long travel in the front of a car is almost synonymous with "A-Arm Suspension." Anything over 15" is usually considered "Long-travel," and as you travel goes up, so are the problems with achieving and maintaining affective travel. Too little travel will limit the speed at which you can drive over the roughest terrain, but too much travel without good engineering will give the car painful and sometimes dangerous handling characteristics.
We use an equal length A arm setup (which is misleading as the rear bar of the arm is slightly longer in order to move the tire center forward) with the upper control arm being a J arm type. Both arms are made of thicker steel than the frame, all parts are chromoly for rigidity and strength, and they are plated for additional strength and a firm feel at the wheel. The more rigid the front end is the more solid the handling will feel due to reduced vibration at the wheel. The A-arm is very long and extends from the center of the car out to the spindle upright; or around 30"! Remember, the wider the better. This allows for massive travel numbers while keeping shock travel numbers small. But we still use longer shocks and here's why...
We have a design that obtains 28" of front end travel, among the top numbers in the entire recreational off-road industry. Few manufacturers can claim this number and include superior handling in the description, but we have done it through extensive research and development. There are two big problems most people run into with this much travel: Bump-steer and body-roll. Bump steer happens as the tire moves in its arc and the front track width narrows at full bump and full droop, and is widened at its center point. This affects handling because as you hit a bump on one side of the car, the track width of the front of the tire is narrowing which turns the car slightly. The affect is increased with the size of the bump as the turn is more drastic. As you drive over bumps the car will feel like it is steering itself. We have minimized this affect through the placement of our steering box and adding a little play into the steering wheel. The placement off the rack determines how much bump steer you will have, and as you can never have NO bump steer, we have gotten down to ALMOST no bump steer. Do not worry, a little play in our steering wheel does not make it feel loose. Our cars handle so tight that you will never miss that 1/4".
And now the big one, Body roll. The problem with center mounted A arms like ours is that you've placed a pivot right at the center of the car, right where it wants to roll! Many companies neglect this problem and take advantage of the travel while running a small shock that costs less, straight from the arm to the frame right above it. We run the shock from the outside of the arm, to the CENTER of the car. It counters the movement totally from the movement of the arms. Now, the shock must be longer, and valved much heavier to run this way because of the drastic angle; in fact, we run the exact same shock length with the exact same valving on the front as on the rear, with lighter spring rates to make up for chassis weight. Our suspension design counters itself during a turn and thus feels less body roll. And with this much travel, feel free to hit the whoops at 120mph, or fling the car 30' in the air or 100' long, our suspension will soak it up every time!
The J arms are only there to hold the tire upright, and control the camber & caster of the tire. We use a J arm specifically because it allows us to run a larger diameter shock and lean it back a little towards the rear of the car in order to achieve the desired compression affect. Otherwise it is just a small a arm where both attachments are on one side of the shock.

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Dual-pivot Trailing Arms

Trailing arm designs are generally based off of the old VW design, where a tube running across the car carried a torsion or "Twist" bar, and two arms bolted onto it going backwards towards where the tire mounts. The torsion bar supports the cars weight and gives the suspension its rebound, and shocks could then be added to smooth the ride out. with the advent of coil-over shocks, the torsion bar became obsolete, but the design is so structurally sound and the suspension behavior so efficient, the trailing arms were retained and mounted to a strong tube that replaced the torsion bar housing.
The same stock dimensions of VW arms are still used as a reference for length and width of the arms, represented as a number by a number or 3 x 3, 5 x 6, etc. A 3 x 3 being 3" longer, and 3" wider than a stock VW trailing arm. The reason for the extra length and width is that you stabilize the car by making it wider, and you also increase the axle length which decreases CV joint angle which increases travel potential...if you don't understand that then just know that longer and wider arms give our cars the 25" of travel they need to soak up the huge whoops and jumps you like to drive over. Our cars are capable of 25" but are limited to 23" so as to preserve the components. One of the problems with more travel is body roll. An off-road car is higher for clearing obstacles, and it has a plush absorbent suspension for soaking up hits, so when you corner the car will lean out of the turn more than an on-road car. The way to counter this is with driving style. Drifting hard turns forces the rear end around while keeping engine RPMs up for acceleration after the turn. Learning this technique is fun, but with high horsepower cars it can cause you to lose control so be careful. The extra width of our track also minimizes the affects of body roll. Cutting brakes make a huge difference in turn radius and minimize body roll as well. By forcing brake on the inside tire, the tranny automatically sends the excess power to the outside tire which needs to move faster to turn harder. The lack of power to the inside and excess of power to the outside make the car feel as if it is turning in place without even moving forward. This will scare the bejebus out of your unsuspecting passengers, but be careful how fast you are moving so as not to roll the car or break a tire bead!



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