Sway bars, also called anti-sway or anti-roll bars, are an extremely important and interesting part of the way that a Polaris RZR (or any other UTV) handles in dynamic scenarios. The general purpose of a sway bar is to connect the behavior of one wheel to the behavior of the other. By connecting the two using a stiff bar, when one wheel rises independently as a result of body roll or a bump, the other is pulled up by the sway bar, this action is what combats body roll. See the illustrations below but note that this reaction happens very, very quickly!
Why do we need them?
The application of sway bars in the off-road world is widely discussed and there are a number of differing opinions. The reason for that is that depending on the way that you use your RZR/UTV/SxS, sway bars may or may not be beneficial. For example, a driver that is frequently crawling technical trails at low speeds may find that the added articulation allowed by the removal of his sway bars helps him have greater control over his vehicle. Conversely, one that does more high speed driving and cornering will likely find that a properly setup sway bar system drastically improves the stability of his or her car.
One thing to note is that the sway bar doesn't simply work to keep the car 'flat'. It works to keep the car's wheels closer to the same level of suspension travel. With that in mind, the examples that I mentioned above are shown in simple diagrams below. Bear with me; I'm an engineer not an artist!
Tell me more!
Now that all seems pretty simple until you consider the fact that to perfectly transfer motion from one wheel to another, a sway bar must be perfectly rigid. The truth is, that just isn't feasible and frankly, it isn't what we usually want. For an all-around well performing machine, we want something between the two examples above. We achieve that by allowing the sway bar to flex, so that 5in of travel on one side might only equal 4in of travel on the other.
The flex/compliance in a Polaris RZR sway bar system comes from three places. The first and most obvious is the bar itself. Sway bars are a form of torsion bar and are typically made to allow a certain amount of twist. The figure below shows the stress in the sway bar during loading.
The second is in the bushings where the sway bar mounts to the chassis of the vehicle. The sway bar pivots in these bushings and the extreme forces will often deform the bushings slightly. The figure below shows the strain in the factory rubber bushings during loading.
Finally, the sway bar endlinks are also a source of compliance. Stock Polaris RZR endlinks are typically rubber bushings with steel sleeves connected by a thin steel rod that's welded to each. The rubber bushings at either end of each end link offer a combined total of four point where deflection can occur. Finally, a figure showing the stress in the factory link. The highest deformation occurs in the bushing area, but the highest stress is at the stress riser where the link is welded. If you've seen an endlink fail, it's likely that it was in this exact spot.
What about upgrades?
The goal of upgrading/tuning your sway bar system isn't to eliminate this twist or deflection, it's to do what you reasonably can to isolate it to the bar itself so that with adjustments to the bar, you can fine tune the way that your RZR reacts. More on that further down.
Elimination of slop that's induced by the sway bar mounting points is relatively simple. A set of upgraded bushings will do just fine where the bar mounts to the RZR.
As far as end links go, there are a few options. The use of radial bearings, rod ends and heim joints eliminates the compliance entirely, but they'll wear out quickly from the vibration and harshness and start making a lot of noisy relatively quickly. These are commonly seen because manufacturers simply need to tap both ends of a short rod and then thread in somebody else's rod end. Most times, those rod ends are cheap and will fail even sooner than normal.
The other option, and the one that BuiltRight Industries opted for is to use a beefy billet aluminum link with a polyurethane bushing at each end. This offers a drastic improvement over the factory links as far as how the vehicle reacts dynamically without the noise and harshness of a radial bearing or rod end. The other benefit of an aftermarket end link is that they're all typically more robust than the factory Polaris units, which are prone to plastic deformation or failure. Click here for more information regarding the BuiltRight Industries End Links.
What about the bar itself?
Tuning your sway bar is certainly the final step of the process. By upgrading your end links, you should definitely feel an immediate improvement in response and effectiveness of even your factory sway bar, which translates to reduced body roll and increased stability in corning. Upgraded sway bars are often made of thicker or more resilient material than the factory bar. Upgraded bars will often use a thicker tubing and may offer multiple mounting points for the end links, which give the end links more or less leverage on eachother, increasing or decreasing the effective stiffness of the sway bar system.
At BuiltRight, we prefer to keep things simple when possible. A wise man once said that "Simplicity is the ultimate sophistication." Of course, we're dealing with some systems that can be quite complex, but for our purposes, fewer parts means fewer failure points. There are some seriously awesome looking sway bars available that use a single straight torsion bar with two machined arms, rather than a single bent piece and if you're looking for the extreme end of the spectrum, systems like that with radial bearing style end links are probably best.
If, like us, you're looking for a well-rounded car that's ready to take some serious abuse, a poly bushing endlink with a one-piece bar is the way to go in our opinion. To that end, you can expect to see a one-piece sway bar upgrade available from us later this summer. Until then, get yourself a set of BuiltRight Industries Sway Bar End Links for the Polaris RZR XP 1000 and XP Turbo for a taste of the improvements to be had by upgrading an often overlooked system on your machine!