TIPS AND HOW TO


Upgrades are in every aspect of our life, including the RV world. We buy an RV and put upgrades in it, maybe we want a bigger TV, or a better stereo system, or more cabinets, or different tires, or….the list goes on and on.   One area of the RV you will want to look at for upgrades is the suspension. Yes, there are upgrades that can be done here to make the handling of your RV better. 
 
Let’s talk about motor homes. The heavier the coach, the less it is affected by the wind hitting the big side of the body. Gas coaches tend to be lighter and are affected more by wind and other elements of traveling. Additionally, gas coaches use leaf spring suspension and not air bags like diesel pushers, thus making them prime candidates for after market upgrades.
 
There are various steering control products out there, but we will discuss the sway bar and panhard rod (commonly referred to as a track bar) here. 
 
Panhard rods have been around for many years and are familiar to anyone acquainted with racing. Recently though, they have come to the forefront of the RV market.
 
Imagine an air-suspended coach sitting on an air bag without any control devices; it would be like sitting on top of a balloon and not being able to sit up straight, as you would keep rolling off.
The devices used to control air-suspension coaches are front to rear radius rods and left to right track bars. All air-suspension coaches have these devices incorporated into their designs. Now, if we look at a leaf spring suspension, which most gas powered coaches have, the leaf spring is used as the radius rod that is front to rear control and typically there is no track bar used on leaf spring suspension. (Note: There is a chassis manufacturer that is using a track bar on the front axle as factory installed equipment.
 
This poses the question – “Why use a track bar on leaf spring suspension?”   It has been found that as time has progressed technology has changed and so have the springs and their mountings. Where once they used metal bushings in the shackle that were threaded in and had zerk fittings which required periodic lubrication, now we find rubber in the eyes of the springs and in the shackles offering a softer ride and less maintenance. Where once shorter springs with more leaves were used, they now use longer springs with less leafs. Why does, this matter you may ask? While the new spring style flexes up and down and gives you a better ride than the old ones, the additional length leads to side to side movement or axle shift.  This leads to customer complaints such as, “I am chasing the coach”, “I’m over-steering” or “The tail is wagging the dog”.   The typical cure would be to add track bars on the front and rear axle. 
 
The myth out there is that when you add a track bar you actually induce side to side movement. The truth of the matter is: Yes, you do, but let’s examine a couple of things before we condemn the track bar. As the suspension moves up and down, the length of rod determines the range of movement left to right. The longer the rod the shorter the suspension travel and the less movement left to right.   All of these have to be considered before abandoning the track bar. Example: Let’s compare this with an air-ride. Air-ride suspension has to have a track bar. If you compare the length of that air ride rod to the typical leaf spring aftermarket track bar, you will see that the air-ride is shorter than the leaf spring aftermarket track bar, so in reality the air-suspension track bar should cause more side to side movement in those coaches, but in reality it doesn’t create an issue with the handling of the coach. 
 
You might say, “I already have a sway bar, why do I need a track bar?”   Let’s talk about the difference between the sway bar and the track bar. These tend to get confused in discussions by the terminology. Both the sway bar and the track bar attach to the frame and the axle, but they do two different things.  
 
SWAY BAR:  Sway bar is usually a round solid piece of steel that is formed in a U-shape or with the ends turned 90 degrees. What this bar does is control top sway; top tippiness or top leaning, whatever you want to call it. The way that this works is that as the coach leans the bar has to twist and the resistance to twisting is what controls the leaning or top tippiness.  
 
PANHARD ROD/TRACK BAR:  Panhard rods are generally called track bars and are typically straight bars, some do have a slight curve for specific applications. They attach the frame to the axle to control the left to right or side to side movement. 
 
So, the difference is, the sway bar controls the leaning or top tippiness of the coach and the track bar controls the side to side movement of the coach. Both have their own job and both can improve the handling of the coach.

 

 

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