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
Modern performance sway bars are designed in programs like Solidworks or CAD, starting wit
Sway bars explained
Basically sway bars reduce roll and dramatically improve handling. They connect one side of the suspension to the other with attachment points generally on the lower A-arms and frame (chassis), and twist to limit the roll during cornering. As the truck enters a corner, centrifugal forces create a body roll force. This force is limited by the twisting actions of the sway bar. The stiffer the sway bar, the more resistance is extended to counteract the body roll. Too much sway bar stiffness creates excess pressure on the outside loaded tire causing a loss of traction. Sway bar stiffness is calculated by the force required to twist one end versus the other and calculated in lb-in.
Sway bars work off of torsional force (twisting motion). Therefore, the material in the center of a solid bar plays little role in the resistance of torsional force. With this in mind, hollow bars eliminate some of the center material and move it to the outside of the tube, where it is most effective. In turn, this produces a sway bar that is lighter in weight and just as stiff, if not stiffer, than solid. For example, a 13⁄8-inch hollow bar is equivalent to a 1¼-inch solid. But the 13⁄8-inch hollow bar is 6-percent stiffer and 43-percent lighter than the 1¼-inch solid.
In most cases, bars need to articulate independently while still tying the axle or control
Years ago, most trucks were only equipped with a front sway bar. Back then, the best tires were skinny with relatively soft sidewalls. Today people are running modern super-sticky tires. These tires produce serious grip and are much better than yesterday's race tires. Your truck will be the quickest and most comfortable around a corner or on your favorite twisty road with a neutral handling balance. This is achieved when the car is neither loose nor tight (excessive understeer or oversteer), but balanced with the front and rear tires doing equal work. Providing that the springs are of sufficient rate to keep the car from bottoming out, the handling balance is tuned with the front and rear sway bars. When talking to suspension designers at Hotchkis Performance, they said they typically engineer the largest front sway bar possible that doesn't overpower the front suspension and then tune (change roll stiffness) with an adjustable rear sway bar.
Some people recommend running a stiff rear spring combination without a rear sway bar. In this case, the heavy spring rate keeps the chassis from rolling, thereby eliminating the need for a rear sway bar. This is fine if the passengers wear kidney belts and interior rattles are no problem, but most truck owners know that a stiff rear spring and an unloaded bed can be brutal on long hauls. The rest of us want a comfortable ride with great handling. Adding a rear sway bar solves the ride quality issue and creates an optimum handling balance. The rear spring rate can be softer for better ride quality and corner exit traction because the rear sway bar (not the springs) is controlling the rear body roll.
Now that we know sway bar roll stiffness minimizes body roll, to make the truck handle well and remain balanced during cornering the front and rear sway bars must be tuned to work together. Well-designed sway packages offer balanced handling and are adjustable to fine tune the handling characteristics to the driver's preference. The adjustment is accomplished with holes in the sway bar end that allows the endlink to be positioned in multiple locations effectively lengthening (softening) or shortening (stiffening) the sway bars. Due to the endlink mounting location and reduced benefits of an adjustable front sway bar, companies like Hotchkis Performance often design the adjustable rear sway bar to be between a two- and four-hole difference. The adjustment holes give the driver a great tuning advantage because each hole is at least 100 lb-in difference.
Here we see (L to R) raw bar stock, a factory small-diameter bar and a performance afterma
This aftermarket bar (L) is adjustable, with three mounting options for different torsiona
The best modern sway bars are created by bending high-quality domestic steel bar stock in
Companies like Hotchkis Performance then use Laser Vector scanners to check bars from ever
How Sway Bars Are Made
Manufacturing a sway bar has been done by various methods throughout the years. The traditional method of making a bar is to take the raw bar stock, and bend it into the shape you want by using a press and bend dies. This is generally a cheap way to make them, and there are several drawbacks to this method. The first such detriment is that each bend is done separately. With each bend the tolerance increases, i.e. inaccuracy, in making the part. This allows for increased human error in production. As trucks become more complex, the packaging of the sway bar tightens. There is less room for error, and thus the part needs to be more accurate to fit in the car. Another disadvantage is that the press bends can add several extreme tooling dents or "marks" to the product. Dents such as these are acceptable on a solid bar, but they make the part less pleasing to look at. Tubular material cannot be bent in this traditional way. The press will either kink or crack the tubing when bending the material.
Companies like Hotchkis use CNC (Computer Numerically Controlled) bending machines and tubular stock. The CNC does all of the bends in one handling process. Raw material is loaded into the machine, which then goes through a series of motions to produce a smoothly bent part. A computer keeps track of each bend in relation to all of the other bends. This produces a very high-tolerance part, typically in the 0.050-inch range or tighter, and with consistent reliability. During the manufacturing run, a Laser Vector inspection system is employed to measure the parts being bent by the machine. This measures the shape of the bar, and compares it to a computer file of the part print. The laser's computer sends any necessary corrections directly to the bending computer. This is done because each batch of raw material varies and bends slightly different than another.
A set of freshly bent bars is waiting to be finished. Some companies weld cast ends to hol
Like all aftermarket products, sway bar testing procedures can vary from company to company. Some of the lower-end products are simply upsized versions of factory parts with increased rates and are not tested at all. The more high-end components like those manufactured by Hotchkis are rigorously tested at the track and on the street for the optimal balance of handling improvement, driver feedback, adjustability, and ride compliance. John Hotchkis states that his company's tests use a 200-foot skid pad, 600-foot slalom, road course, and street drive tests to ensure every system works correctly.
In conclusion, a well-designed, lighter tubular sway bar package is the best handling benefit you can bolt on to your classic truck. The next step in the bolt-on handling equation is a set of premium shocks. These will make a world of difference and improve overall suspension performance and ride quality.
After testing, engineers will finalize a design and include specs for bushings, hardware,
This is Hotchkis Sport Sway Bar kit for the Chevy C10 pickup. Note the unusual rear sway b
The blade type bar offers adjustability like a traditional sway bar, but provides more art
Endlinks are what attach the sway bar to the suspension. In many cases, factory endlinks (
Standard sway bar bushing brackets are usually "strap" style brackets made from pressing a
After sway bar installation, it's often a good idea to align the truck with a performance