A sway bar is a torsion bar mounted laterally on a suspension and is designed to reduce side sway. The sway bar attempts to accomplish this task by transferring movement from one side of the suspension to the other. This is done through the connection of a torsion bar to each side of an axle by flexible links. A sway bar is a good choice to improve handling if the vehicle has a sufficiently strong suspension and thr shock absorbers are in good condition.
Second only to the suspension springs, shock absorbers provide the primary control against sway and are the basic handling control product. Although confusion abounds in regard to types and sizes of shock absorbers, certain rules apply to base a comparison upon. Principally there are two basic types of shock absorbers today: gas and oil as well as air assisted and coil spring assisted . Shock absorbers should be considered first when suspension modifications are considered necessary.
Air Bags are an add-on air support system which provide suspension assist through the use of rubber air bellows. These air systems provide their owner with control over the amount of increased load capacity by the control of air pressure. They are available in either kit form with installation brackets and hardware, or as an insert inside already installed coil springs.
Auxiliary Springs, or Overloads, is a broad based term used to describe a spring which provides an added assist when required. Although many products on the market are called auxiliary springs, many fall short of the mark. Designs vary from frame mount to U-bolt mounted variable auxiliary spring designs.
Usually the lowest priced alternative is an “Add-A-Leaf”. It is a one size fits all extra leaf that is added to a leaf spring. This leaf's principal purpose is to provide added clearance by forcing the spring to bend upward near it's center.
Spring Rebuilding and Reinforcing is a process where a spring is re-configured with additional leafs and rearched to provide improved carrying capacity and ride control. This process is performed by a spring shop and involves the removal of a vehicle's springs and then their subsequent repair and re-configuration.
What's Wrong with my Rig?
Today it is easy to find any number of conflicting recommendations when it comes to curing a handling or suspension problem. It is first important to understand why you are having a particular problem before you try to cure it.
As a vehicle approaches it's rated capacity, it's deflection or movement increases. As this movement increases, control is reduced and this loss of control is what is commonly referred to as sway, bounce, swerve, etc. This motion is increased as the center of gravity gets higher and/or as side or cross wind increases.
The first step is to understand what you are trying to cure. Sway is a sideways rocking felt high in your back and is caused by excess suspension movement usually during turning, side winds or uneven road beds. The easiest test is to drive at a slow speed while turning the wheel left and right. The rocking you feel is sway.
To further confuse, skating is a motion where the vehicle moves laterally (side to side) but does not rock. This is usually felt very low or beneath your seat. This motion is caused by tire flex and is due to improper tire choice for the load or mis-matched or under-inflated tires.
A host of handling problems remain the sole purpose of the alignment industry. The correct operation of a vehicle's steering geometry goes hand in hand with the correct operation of it's suspension. Symptoms such as pull, push, darting and shimmy are diagnosed through steering geometry. Don't be afraid to ask questions and insist upon understandable answers. Have your service provider explain how a particular product will correct your situation.
Now that sideways motion has been discussed, an understanding of up and down motion is important. As the interstate highways age, the handling problems due to poor road condition increase. It has gotten to the point that some RV's require their drivers to physically stop their vehicles to stop a harmonic bounce. The cause can be one of poor weight distribution or worn or failed shock absorbers. Of course, the easiest problem to diagnose occurs when you drag the rear of your RV on the ground.
You will save a great deal of time and misery by clearly communicating what your RV’s performance. By being informed, you can make smarter choices as well as stand a better chance of getting what you need at a price you expect. Either way, be informed.
Is an Auxiliary Spring the answer?
An Auxiliary Spring represents a solution for a wide array of problems from increased carrying capacity to reduced sway. It is important to understand where they can be correctly applied and where they can not. Although an off the shelf alternative sometimes is a good and correct choice, many times this will not hold true.
An auxiliary spring, by nature, is designed to be somewhat load sensitive. In other words the auxiliary spring is intended not to come into operation until a vehicle is loaded. On a normal pickup that carries a camper four weekends a year, this represents the best solution for both ride and carrying capacity for a part time load. A motorhome requires a different solution. The time delay designed into an auxiliary spring before it begins to work represents wasted suspension movement. Since we can assume that no motorhome will ever be "empty", an auxiliary spring's ride saving features end up wasted. This lost motion represents many scraped bumpers and excess sway.
Most importantly, the solution you choose should directly address the problem you are trying to cure. Since all the suspension components are designed to interrelate with each other, the best solution may not be easy or simple.
As with any product you consider, the fundamental comparison is one of value vs performance. A pair of clamps and a single leaf cannot be expected to provide the two thousand pounds of capacity that an advertisement might say, especially if it costs $19.95. Likewise, a 3000# auxiliary spring kitis not a safe solution for a mini pickup. Understanding the loads in question and the safe operating range of your vehicle, is of paramount importance when considering suspension modifications.
What is a Safe Load?
The answer to this question lies in your vehicle. It can show you what constitutes a safe load. If you know where to begin your search, you can understand what your limitations are. First and foremost, look at the basic rating. Somewhere on your vehicle is a GVW rating or Gross Vehicle Weight rating. This represents what the chassis manufacturer designed this vehicle's maximum weight to be. The rating is usually broken down into individual front and rear ratings and usually represents the maximum rating of the weakest component on the suspension system. These ratings include the tires, wheels, bearings, axles, springs, shocks, brakes, etc. etc. etc.
First, let's consider the Tires. On the side wall of all tires currently produced is some information about your tire's limitations. First, a commonly known item is the tire's load range. This is a rating expressed with a single letter and is a basic tire selection guide. However, if we look a little closer, we will see a weight rating and a air pressure spec. This tells us what this tire is rated to carry at the specified air pressure. By overloading or under inflating this tire, we run the risk of allowing it to overheat and thus fail catastrophically. The correct tire pressure for a given tire is a function of the weight on that tire, not of it's rated capacity. Tire manufacturers maintain air pressure statistics for their tires and are available on request. If you have any concerns regarding tire selection, air pressure or tire capacities, consult a reputable tire service center.
Second, let's consider the Axles/Brakes. Although, harder to determine, manufactures also rate axle and brake combinations. Usually an axle will be correctly chosen and will be of sufficient capacity. When abnormal wear on brakes, bearings or seals occurs, careful consideration of your drive train is in order.
Third, what about the springs and shocks? Springs have a weight rating that represents the design load for that particular spring. The limiting factor for a GVW rating is usually the springs. As a spring load approaches it's rated capacity, it's deflection increases. As deflection or movement increases, it's stability decreases. Correct shock sizing is most important here.
Fourth, what's left? Although it may be difficult to improve on what's left, it is important to consider that the rest of the drive train and the frame have limitations. These items have been designed for a specific purpose and designed load. Before you add weight, trailer hitches and assorted carriers, consider the ramifications of your increased load.
What can I carry? In order to answer this question we need to weigh the vehicle and do some math. Here is a recent example: Remember though, it is never safe to overload a vehicle.
A Class "C" Motorhome. First we weighed the Motorhome. With a total weight of 9,700#, a G ross Vehicle Weight rating of 10,000#, although close, everything appeared within specs. Since the owner had complained he was scraping driveways and he experienced excessive sway, we investigated further. Next we weighed the rear of the RV. The rear of a vehicle weighed 7,490#, and had a rear end rating (GVW REAR) of 6,500# meaning a overload on the rear end by over 1,000#. Both the tires and suspension system required modification.