Until recently, truck owners had very limited choices when it came to their suspension: leave it stock and suffer through excessively sloppy handling and body roll reminiscent of a rowboat during high seas, slam the truck with drop springs and get a spine-jarring ride, or use an expensive airbag kit that provides a perfect stance, but will have its limits when using sway bars. One easy way to improve handling and overall drivability is to control body roll and improve traction with aftermarket sway bars, or antiroll bars as they're sometimes known.
Here we have a real-world example of body roll. The huge gap between the top of the tire a
Nearly every truck produced in the last 75 years came equipped with at least one sway bar from the factory, but OEM cost-cutting and ride-quality considerations meant most trucks rolled off the showroom floor with very small-diameter bars that kept suspension geometry in check, but didn't do much to control body roll or handling.
Luckily, aftermarket sway bar technology has improved dramatically in the last decade with hollow tube technology leading the way. Gone are the days sway bars were produced from extremely heavy solid bar stock. Now superior CNC bending equipment and precise engineering allows for lighter tubular sway bars possessing the twist resistance of solid bars with a fraction of the weight. Lighter, more efficient sway bar packages are standard equipment on new vehicles ranging from new Silverado pickups to Corvette ZR1s and a Porsche Turbos.
They key to understanding sway bars in the classic truck market is that well-engineered sport sway bars made in the USA by a reputable company will provide more handling improvement and fun than nearly anything else you can do to your truck, and most kits can be installed with handtools in a few hours.
This truck has performance sway bars and has minimal body roll going into the corner. Note
Nearly all trucks new and old come set up from the factory with significant understeer as a safety precaution. Understeer, also called "push," is what happens when you enter a turn at a high rate of speed and front tires howl, while the car continues to move forward in a straight line. Essentially the rear tires are overpowering the front tires and the vehicle goes straight.
"Oversteer" is when the front tires stick and the vehicles turns into the corner while the rear tires lose traction and the rear of the vehicle tries to rotate around the perimeter of the turn. While dangerous for a novice driver, an experienced hot shoe can control this with the throttle for more aggressive driving.
Sway bars can provide adjustments to driving dynamics like understeer and oversteer by transferring weight to different corners of the suspension as the vehicle navigates a corner. In many cases adding a rear sway bar when there isn't one from the factory, or adding a stiffer rear sway bar, can make a system designed to understeer either neutral or oversteer.
Body roll is a reference to the load transfer of a vehicle toward the outside of a turn. When a vehicle is fitted with a suspension package, it works to keep the tires in contact with the road, providing grip for the driver to control the vehicle's direction. This suspension is compliant to some degree, allowing the vehicle body, which sits upon the suspension, to lean in the direction of the perceived centrifugal force acting upon the car. Sway bars are a part of the suspension specifically designed to address body roll.
Body roll of the vehicle (body and chassis) relative to the ground is not necessarily bad. Most performance suspension setups try to keep the frame of the vehicle as parallel to the ground as possible to maximize tire contact patch (aka handling). However, completely eliminating body roll can also create a very stiff ride, so finding a balance that keeps the suspension geometry working correctly and the body parallel to the ground (thereby controlling the vehicle's center of gravity) while also maintaining a comfortable ride is the key.
Why should you change your antiroll bars from the stock ones? Well it's pretty simple. Enthusiasts typically demand more from their cars than the average driver. They need improved handling, increased high-speed stability, and better traction. Properly designed and tested antiroll bars give a car, truck, or SUV optimum handling potential and chassis balance. This is accomplished during testing by changing the roll couple (changing the stiffness of the front versus rear antiroll bars) to achieve the optimum handling balance.
Generally, the factory setup on a performance vehicle is neutral to slight understeer, but it depends on the application and vehicle. Auto manufacturers are out to give the average person the car that will suit most of their needs. If they install larger antiroll bars, stiffer springs, and lower the car, they will create more customers that are dissatisfied with their car than if they offer a "detuned" car. They opt to cut cost, and raise customer satisfaction ratings by offering a decent, if not mediocre, car. This leaves considerable room for increases in the suspension's performance or "tuning" using aftermarket parts.
A pretty standard performance sway bar kit – tubular front and rear non-adjustable bars. N
In figure 1, we see a chassis with no body roll, and maximum tire contact patch. In figure
This simple line drawing explains how the sway bar works. By tying the frame to the contro