Can I make my RV handle better? Upgrading your RV motorhome sway bars will make your RV handle much better.
Does the thought of a sharp turn, wind gust or a passing tractor trailer make you white knuckle when driving your RV? Upgrading the factory sway bars will make a major improvement. This article is tailored to 2008+ Class C RVs built on a Ford E-450 chassis, however the approach is similar for all Class A and class C RVs (part numbers and procedures will vary). This is a pretty easy DIY upgrade and would rate this a 3 out of 10 in terms of difficulty.
Sway Bar Options
There are two primary options if you want to upgrade your factory sway bar(s) to stronger versions. Roadmaster Incorporated manufactures what they call “Roadmaster Suspension Solutions” (RSS) sway bars for all types of motorized RVs. Another option is a set of sway bars manufactured by Hellwig Products. Based on my research, both products are comparable in specifications, however the Hellwig is about 1/2 the cost.
Front Sway Bar Upgrade
For the front axle of my Class C RV, I went with Hellwig sway bar part number 7718 ( since it was reasonably priced and very beefy). The Hellwig 7718 sway bar is designed for the 2008+ Ford E-350 and E-450 chassis. Below is a photo of the Hellwig 7718 compared to the original Ford sway bar. Using my dial calipers, I measured the diameter of the factory bar at just over 7/8 inches (0.915 inches). The Hellwig bar measured slightly larger than 1 3/8 inches (1.368 inches), making it approximately 1/2 inch (1.5 times) larger than the stock Ford sway bar. This upgraded sway bar comes with bushings that are upgraded from a rubber to a stiff polyurethane to minimize sway bar deflection when loaded. It reuses the factory ‘dog bone’ end links.
Factory “dog bone” end link
Front sway bar comparison
This is the process I used to install my new front sway bar. Before starting the installation, I strongly advise to carefully review the instructions that came with the new sway bar. I also recommend soliciting the help from someone to make this job easier.
I recommend removal and installation of sway bars to be done with the suspension loaded and on the ground. To remove the stock front sway bar, first remove the two 18 mm nuts holding the ‘dog bone’ end links to the suspension on each side of the bar (note the orientation of the end links as they will go back on the same way with the new sway bar). If the studs turn while trying to loosen these nuts, you can insert a 19 mm open end wrench on the other side of the sway bar (there are machined flats on the stud). Once both of the nuts are removed, the end link should slide out. Repeat this to remove the end link on the other side of the sway bar. Keep both end links and the four nuts as they will be reused.
The sway bar is now supported by two bushings attached to the RV frame. The front bolt on each side is 18 mm and has factory-applied thread locker. These two bolts will be difficult to remove with hand tools and will likely require a pneumatic impact gun or a large breaker bar. The rear bolts are 15 mm and are easy to remove by hand. I suggest having a second person help support the sway bar while removing these four bolts. Once they are removed, the sway bar will be loose and can be removed. Retain these four bolts as they will be reused.
It is now time to prepare the new sway bar for installation. Apply the supplied lubricant on the inside of the new polyurethane bushings and install them on the new sway bar in the same approximate locations as the rubber bushings on the stock sway bar. The large ‘U’ brackets slide over the bushings with the larger of the two holes facing the front of the sway bar. The smaller bracket goes on the other side of the bushing to provide it support. The correct configuration is shown in the comparison photo above.
With the assistance of a helper, slide the new sway bar in place and thread the two 15 mm bolts loosely through the rear holes of the brackets and into the frame (only a few turns to engage the threads is OK) . Repeat with the two 18 mm bolts (do not apply any thread locker at the time). Install the two end links in the same orientation as they were with the stock sway bar and install the two 18 mm nuts and torque them to 57 lb-ft. Repeat this process for the other end link. Slide the sway bar side-to-side until both end links are roughly vertical. Temporarily remove one of the two 18 mm bolts holding one of the two bushing brackets. Apply medium thread locker (i.e., blue Loctite) to the threads of this bolt and reinstall loosely. Note that the brackets have slotted holes to allow front-to-back adjustment. Move the bracket to get the end link nearly vertical and tighten the 18 mm bolt to 111 ft-lb and the 15 mm bolt to 18 ft-lb. Repeat this for the other bracket. Verify everything has ample clearance and adjust as necessary.
The installed Hellwig sway bar is shown below.
Front Hellwig sway bar installed
Rear Sway Bar Upgrade
For the rear axle of my Class C RV, I went with Hellwig sway bar part number 7180 since it was reasonably priced and very beefy. The Hellwig 7180 sway bar is designed for the 1997+ Ford E-450 chassis. Below is a photo of the Hellwig 7180 compared to the original Ford sway bar. Using my dial calipers, I measured the diameter of the factory bar at just over 1 1/8 inches (1.137 inches). The Hellwig bar measured just under 1 1/2 inches (1.479 inches), making it approximately 3/8 inch (1.3 times) larger than the stock Ford sway bar. This upgraded sway bar comes with bushings that are upgraded from a rubber to a stiff polyurethane to minimize sway bar deflection when loaded. It also comes with new end links and polyurethane bushings on the upper and lower interfaces.
Rear sway bar comparison
This is the process I used to install my new rear sway bar. Before starting the installation, I strongly advise to carefully review the instructions that came with the new sway bar. I also recommend soliciting the help from someone to make this job easier.
I recommend removal and installation of sway bars to be done with the suspension loaded and on the ground. To remove the stock rear sway bar, first remove the 15 mm bolt holding the top of the end link to the side of the frame. Repeat this to remove the end link from the frame on the other side of the RV. Keep both bolts as they will be reused.
The sway bar is now supported by two bushings attached to the RV rear axle assembly. There are two 13mm bolts on each side. I suggest having a second person help support the sway bar while removing these four bolts. Once they are removed, the sway bar will be loose and can be removed. The four bolts will not be reused.
It is now time to prepare the new sway bar for installation. Apply the supplied lubricant on the inside of the new polyurethane bushings and install them on the new sway bar in the same approximate locations as the rubber bushings on the stock sway bar. The large ‘U’ brackets slide over the bushings with the larger of the two holes facing the front of the sway bar. The thick steel plates go on the back side of the bushing (between the bushing and the rear axle housing). I only installed the end links in the photo above for illustrative purposes. I do not recommend installing them at this time.
With the assistance of a helper, slide the new sway bar in place and thread one of the four supplied 17 mm bolts loosely through the the ‘U’ bracket, the thick steel plate (supplied with the kit) and thread a few turns into the rear axle housing. Repeat for the other three 17 mm bolts in their respective holes.
The new end links need to be prepared before installation. First apply lubrication to the two upper polyurethane and steel bushings. I used a block of wood and a rubber mallet to drive the polyurethane bushing into each end link. I used my bench vise to press the steel bushing into each of these polyurethane bushings. For the threaded side, install the thin jam nut so the top of the nut is approximately 1.3 inches from the end of the threads. I used my dial calipers to do this, but setting to 1 5/16″ using a tape measure will be close enough. Next thread the taller nut up against the jam nut and tighten them tight against each other using two 7/8″ wrenches. This needs to be done for both end links. To install slide the factory 15 mm bolt through one of the supplied washers and loosely bolt the end link to the side of one of the frame rails. Do not tighten yet. Next slide a washer against the large nut previously installed (the one against the jam nut), then slide one of the remaining polyurethane bushings with the raised lip facing downward. Rotate the sway bar to insert the end link stud through the hole at the end of the sway bar ‘arm’. Next slide another polyurethane bushing, with the raised edge facing up, then another washer. Lastly, thread one of the nylon lock nuts a few turns (do not tighten yet). For the other side, the process is similar, except you have to install the end link loosely on the sway bar (using the same washer, bushing, and lock nut configuration) then bolt the upper part of the end link to the side of the frame using the factory 15 mm bolt and washer. I haven’t found definitive torque values for the center bushing or the end link bolts and honestly tightened mine by feel. You may want to consult with your local Ford dealer if you want exact ford recommendations. Lastly, tighten the bottom end link lock nuts until the bushings supporting the sway bar just begin to deform. Verify the arms of the sway bar are horizontal and make any necessary adjustments if necessary.
The installed Hellwig rear sway bar is shown below.
Rear Hellwig sway bar installed
How Sway Bars Work
Sway bars (actually they are technically anti-sway bars but are generally referred to simply as sway bars) are designed to resist unequal motions of each side of the suspension. A simplistic example is shown below. Suppose there is a strong wind gust that hits the passenger side of an RV while driving down the highway. This wind gust will try to push the RV towards the driver side. To counteract this, the driver of the RV will need to steer the RV toward the passenger side. The effect on the RV is that it will want to roll the entire body of the toward the driver side. Not only can this make you sea sick, it is inherently dangerous. If the roll is severe enough, it can cause the driver to lose control of the RV. This is not only the case in windy conditions as this roll happens any time the RV is steered to the right or left (i.e., driving around a curve). The harder the turn, the more severe the roll will be.
Vehicle manufacturers install sway bars on the front and rear suspensions to try to counter the forces that cause body roll. With RVs typically weighing tens of thousands of pounds and with elevated centers of gravity (tall vehicles roll more than sports cars), the amount of force induced during body roll is substantial. Upgrading the sway bars increase the forces that counteract body roll. The question is…how exactly do they work?
Effects of wind or turning on an RV
Sway bars are bent pieces of steel round bar that are supported at four points as shown below (two mounting holes and two bushings).
Generic sway bar
Along the center of the sway bar, there are two bushings that the sway bar runs through. These bushings are supported by a solid structure (generally the vehicle frame in the front and the rear axle housing in the rear). The sway bar can freely rotate around these bushings. At the ends of of the sway bar are ‘arms’ that attach to either the front suspension in the front or the RV frame in the rear using end links. The end links connect the legs of the sway bar to the RV but allow enough horizontal motion to prevent binding. If the vehicle suspension moves evenly up and down, the sway bar will simply rotate in the bushings and provide minimal resistance to this motion. However, if the suspension does not move evenly (i.e. left tire moves upward and right tire moves downward), the bar will twist and the resulting torsional forces will counteract that loading. Fred Puhn, in his book “How to Make Your Car Handle,” presented an equation to estimate the stiffness of a typical steel sway bar. Using the simple diagram above, the stiffness of a sway bar (K) can be estimated as:
Sway bar stiffness equation
where:
- A is length of end perpendicular to B (inches)
- B is the length of the center part of the sway bar (inches)
- C is the length of the sway bar “arm” (inches)
- D is the diameter of the sway bar (inches)
- K is the torsional stiffness (lbs/inch)
For a direct swap sway bar, all of the length measurements should be same (only the diameter is increased), therefore the stiffness ratio between the new and stock sway bars can be written as:
Upgraded sway bar stiffness equation
Based on the ratio of the measured diameters of 1.3 to 1.5 (i.e., the diameter or the Hellwig bars are 1.3 (rear) and 1.5 (front) times larger than the stock sway bars), the torsional stiffness will increase three to five times compared to the stock sway bar! That increase significantly counteracts the tendency of the RV to want to roll over. The biggest negative of this increased stiffness is the overall ride can be a bit harsher, however the overall weight of the RV tends to negate this harshness.
My overall impression
Shortly after doing this upgrade, we went on a 1000 mile trip through New England and the Mid West. There was a pronounced reduction in vehicle sway when going around curves and when changing lanes. Wind gusts would still push the vehicle a bit, but not as harsh as it was with stock sway bars. Overall it made driving the RV more like driving a SUV (albeit a very large one!). This significantly reduced driver fatigue and made the driving experience much more enjoyable.
Conclusion
Upgrading the factory sway bars on your RV motorhome will make a major improvement in drivability. Stronger sway bars can be five times stronger than factory sway bars and will significantly reduce the amount of body roll caused by windy conditions or when going around curves. Upgraded sway bars can enhance the overall driving experience by making it much more enjoyable with less fatigue caused by constantly stressing over undesired vehicle body motion.