What Does A Sway Bar Do?

[BajaRon]

I get a lot of questions about sway bars and what they will actually do for the Spyder. Hopefully, the information below will give you a better idea of how this very critical component works with your shocks and suspension to improve handling and stability.

To understand what my sway bar will do for you, you have to understand what a sway bar does and how your suspension works. It isn’t rocket science, but it is a subject that is widely misunderstood. Sway bars, as with suspension in general, isn’t something that most people are well versed in.

This is in no way an exhaustive treatment of this subject so bear that in mind.

A sway bar (or Anti-Sway Bar) is simply a SPRING which lurks under most vehicles produced today, quietly doing their job with little or no recognition. While the sway bar is a huge component in racing vehicles. It is also critical for the every day driver as it controls aspects of handling and control that no other component can.

There are several suspension components that work together to give us a safe, controlled and comfortable ride. Improve any one of them and you will likely see immediate improvement in the area(s) that are affected by that component. It would be foolish for BRP to build the best possible suspension for our Spyders as that would be very expensive and not necessarily appreciated by every customer.

Stock suspension on our Spyders is adequate. Yet there is a great deal of improvement to be had if the owner would like better, more controlled handling.

What we are addressing in this explanation are the effects of centrifugal force (lean angle in a turn) or any side forces (wind, buffeting when passing a large truck, etc.) and how to best counteract these forces, most notably in the case of our Spyders, excessive lean.

There is much more to our suspension, shocks in particular, than just countering centrifugal force. But for this explanation I am only discussing lean angle aspects.

My drawings are crude, but hopefully helpful. Art is not my strong suit!

EffectsShockSwayBar.jpg

1st Picture
This depicts the Spyder going straight ahead without Shocks or Sway Bar. Just 1 A-Arm is shown on each side to keep things simple. The sway bar has zero effect running straight ahead (unless there is a cross wind or buffeting as in passing a large truck on the freeway. Shocks also have little effect when running straight ahead other than to absorb any bumps in the road. Of course the springs on the shocks hold the Spyder up.

2nd Picture
Suspension and body of the Spyder reacts to Centrifugal force (Yellow Arrow) causing the body of the Spyder (Blue Box) to lean to the outside of the turn (exactly the opposite of lean angle on 2 wheels where you must lean to the inside of the turn.) The Spyder does not compensate for centrifugal force. Instead, it attempts to manage it. How well a Spyder manages centrifugal force depends on many factors including the shocks and sway bar. On 2 wheels, centrifugal force must be perfectly balanced. This is done by leaning into the turn.

3rd Picture
Shock springs provide equal down force (Green Arrows) holding your Spyder up. Stiffer spring setting will raise the Spyder. A weaker spring setting will lower your Spyder.

4th Picture
Inside Shock - During a turn the Shock on the inside of the turn (away from the lean angle) extends. This lengthens the spring and reduces down force to that wheel. Though down force is reduced, this inside shock spring is still contributing to lean angle by pushing down on the suspension and raising the high side of the Spyder body, thus adding to lean angle to some degree. This happens until the inside wheel is lifted off the ground. At this point the inside shock has no effect on lean angle.

Outside Shock – While turning, the Outside Shock is compressed reducing spring length which greatly increases down force to that wheel. This increased down force resists lean angle.

The greater the lean angle, the more pronounced both of these shock spring effects are. Here are some basic rules of thumb regarding shock spring effects.

Lower spring Pre-Load setting, lower ride height, increased lean angle in turns, softer, more compliant ride.

Higher spring Pre-Load setting, increased ride height, less lean angle in turns, harsher, less compliant ride.

5th Picture
Remember, the Sway Bar is a Spring attached at 2 points on the frame (Blue Box). The ends of the sway bar are attached to the A-Arms. When going straight ahead the Sway Bar has no effect on the suspension what-so-ever. Therefore, a stiffer sway bar cannot effect the harshness or softness of your ride. The sway bar does not hold your Spyder up, so changing the sway bar will not affect ride height or front end alignment.

6th Picture
A sway bar WILL NOT eliminate lean. You actually need lean to make everything go smoothly. It is the AMOUNT of lean that you want to better control with the sway bar.

A sway bar is simply a straight spring. As with all springs, it is designed to flex with increasing resistance to increased force applied. You can see in this exaggerated picture that a great deal of stress is being applied to the sway bar due to the lean angle of the Spyder body (Blue Box). The sway bar is attached to the frame at 2 points. It does not actually bend as depicted, but it is difficult to show how this torsion spring works with my limited skills in diagramming.

The Sway Bar is always working to stay straight. As the lean increases the Sway Bar applies increasing force to each A-Arm in its attempt to remain straight. Using leverage created by the angle of the A-Arms, the Sway Bar applies force to the Spyder Body (Blue Box) in the opposite direction to the lean created by side force.

Once you ride a Spyder with a Custom Performance Sway Bar, you won't need to know any of this because you will be able to feel exactly what I'm talking about every time you encounter a situation where your Spyder used to lean too much.

I sincerely hope this helps! Being well informed is the best tool any Spyder owner can have in their tool box.