Why the Instability?

[Metalman]

We took a four hundred plus mile trip over the Thanksgiving weekend and encountered severe crosswinds. Even though we were pulling a sizable trailer, the RV (Windsport 27K) lunged across the solid center line by a foot or more. It was like someone lifted the front end and slid it sideways. The steering wheel didn't move much if any, since I was holding it with two hands. Generally winds or road conditions don't give me much trouble.

I understand that some owners are installing aftermarket equipment to help with such handling problems. My question is what is going on with the suspension or the steering that causes this unstable situation and how do these add-on components take care of the problem?

[brucev]

I have the Hurricane 27K and I am still trying to get the handling within reason. I added front and rear Roadmaster sway bars that helped a lot, I just ordered the Roadmaster RSSA & RBK9 steering stabilizer on sale at Camping World that should be delivered this week. I had it aligned two weeks ago but that didn't really do anything because mine was not far out of spec. The last thing I will add is the Davis TruTrac. Expensive mods but for me it was one of safety. My 2nd trip out I hit strong cross winds and a couple times it blew me off the side of a narrow 2 lane road and when it hit the soft shoulder I almost lost it. Good luck and safe travels!

[Metalman]

I understand that there are handling and stability issues with motor homes, but what I don't understand is specifically what causes them to wander so far from the straight and narrow. It is slop in the tie rod end, ball joints (or king pins), play in the steering linkage, or simply too much broad side for tire traction? Further I'd like to know how these add-on devices improve the situation.

[Beacher]

Specifically, your motorhome is non-aerodynamically shaped more or less like a big box of Saltine crackers, with a very high center of gravity.

When a mild crosswind, (or a passing truck's wind), hits the side of your rig as it's traveling down the road, approximately 2,300 pounds of wind energy force is pushing to one side, against the cracker box shaped side.

In a strong crosswind, up to 3,500 pounds of force can immediately and randomly hit the side of your rig, pushing you out of your lane.

In winds over 60mpg you really want to park somewhere protected, (any mobile home park in the midwest will do)! America can then watch the RVs and mobile homes being blown around on the 11 o'clock news.

[Metalman]

Originally Posted by Beacher

Specifically, your motorhome is non-aerodynamically shaped more or less like a big box of Saltine crackers, with a very high center of gravity.

When a mild crosswind, (or a passing truck's wind), hits the side of your rig as it's traveling down the road, approximately 2,300 pounds of wind energy force is pushing to one side, against the cracker box shaped side.

In a strong crosswind, up to 3,500 pounds of force can immediately and randomly hit the side of your rig, pushing you out of your lane.

In winds over 60mpg you really want to park somewhere protected, (any mobile home park in the midwest will do)! America can then watch the RVs and mobile homes being blown around on the 11 o'clock news.

I understand the aerodynamics of our big, boxy RVs. And if the wind is actually moving the RV sideways, then how do aftermarket stabilizing systems prevent this? I can't imagine the front end of the RV being slid across the road. I suspect it's some kind of an interaction of the body, chassis, steering, and suspension components. Until the big gust last weekend, I have been pretty successful at keeping the RV between the center and edge lines.

[brucev]

Metalman, I am not technical enough to understand all the physics of suspension systems, but I believe it is the way the coaches are built and the need to keep costs down so they opt for marginal components. The sway bars I had installed were somewhat larger than stock which reduced the rocking motion and sway caused by passing trucks considerably. I expect the steering stabilizer to tighten up the front end and help with soft steering, the tendency to wander and rut tracking. I don’t want to make this a Roadmaster commercial because it seems all the manufacturers have their fans depending on the brand installed. I have a Roadmaster tow bar and Sway bars so I opted for their steering stabilizer too (and it was on sale at CW). I would suggest you call Roadmaster customer service department and I bet they have someone that will answer your questions. I have spoken with them twice and they seem to be knowledgeable and willing to help. You can also go to their web page and probably any other manufacturer’s web page and get answers to your questions.
Roadmaster Inc. - Tow Bars, Braking Systems & RV Accessories
Then there is also YouTube. I have seen a few videos about blowouts that helped convince me to spend the money. Also, keep coming back to this thread as more answers and opinions are submitted and eventually you will get the details you are looking for.

[Lloyd]

Originally Posted by Metalman

I understand the aerodynamics of our big, boxy RVs. And if the wind is actually moving the RV sideways, then how do aftermarket stabilizing systems prevent this? I can't imagine the front end of the RV being slid across the road. I suspect it's some kind of an interaction of the body, chassis, steering, and suspension components. Until the big gust last weekend, I have been pretty successful at keeping the RV between the center and edge lines.

Until RV manufactures quit putting those big boxes on a suspension that is to light for it, the problem isn't going away.

[Chance]

Originally Posted by Metalman

I understand the aerodynamics of our big, boxy RVs. And if the wind is actually moving the RV sideways, then how do aftermarket stabilizing systems prevent this? I can't imagine the front end of the RV being slid across the road. I suspect it's some kind of an interaction of the body, chassis, steering, and suspension components. Until the big gust last weekend, I have been pretty successful at keeping the RV between the center and edge lines.

Your motorhome is probably not sliding as if the tires lose traction. My guess is that it's a combination of tire slip angle plus steering being affected by the side forces which roll the body on the axles.

Solid axles front and back with leaf springs as used on F53 chassis is also relatively crude by automotive standard. These are not going to handle like a car.

Also, if the wind is strong enough it will blow just about any vehicle off the road. A strong gust once blew me off into shoulder while driving a relatively stable minivan. I'm not sure what it would have done to an RV, but expect it would have been far worse.

[Metalman]

Thanks for all of the replies. I guess it's a combination of factors that is creating the instability problems. I suppose if the big box is tilted, the suspension on one side is compressed and the other side is streached. That probably will cause movement in the steering mechanism, which I suppose both heavy duty sway bars and steering stabilizers will minimize.

We've used the motor home for over 6,000 miles and have and only one potentially bad situation. If it happens again, I might consider adding components to reduce the problem.

[THOMAS]

I installed safety plus on front and super steer rear track bar it is like a different coach trucks don't push it around on highway as much but your going to get a little push when certain shaped trucks blow buy

[THOMAS]

also mine came with large front sway bar is this standard any one know?

[Chance]

Originally Posted by THOMAS

also mine came with large front sway bar is this standard any one know?

Ford specs list them as standard. They add suspension stiffness against roll, but can't overcome or undo inherent issues associated with bad design.

Adding stiffer sway bars can make a vehicle "feel" more stable, but the underlying problems may still be there. For example, if the motorhome's center of gravity is too high, adding stiffer sway bars can limit the motorhome from leaning as much on curves, but the transfer of forces (weight) to the outside tires is much the same. The driver may feel safer right up to the point where the RV rolls over on its side.

Having some advanced warning that the driver is approaching the limits is not necessarily a bad thing.


Sway bars that are too stiff also degrades ride quality.

[petef]

There is a huge long thread on another forum about this, google CHF. It involves moving the sway links to the inner hole on the sway bars, front and rear.
I have done that modification using the extended links on the front ( needed on the 27k) and also had a Tiger or Blue ox, don't remember, rear trac bar installed. It makes the rig less apt to be pushed around by winds and road conditions. It worked well. The height, box shape and weights combined moving up, down, sideways and yaw make these motorhomes hard to drive. When it gets extreme windy it is better to stop and wait as driving is tougher and your gas mileage gets very bad as well, stop and rest and relax. I have driven in 30-40 with 50 gusts without problems now, but it tiring so won't do it for long.

[EA37TS]

Same things are true about cars and SUVs, it's just they aren't as big. I have driven through the Midwest, particularly from Kansas City to Colorado. Driving along the interstate with high crosswinds will cause you to hold the wheel to one side or another and then rapidly correct when going under an overpass or when a truck passes and blocks the crosswind.

[Chance]

Originally Posted by dstankov

Same things are true about cars and SUVs, it's just they aren't as big. ....cut.....

This is so true.

A few years ago I was following my wife from Houston to San Antonio in a strong cross wind out of the Gulf; she was driving an Odyssey minivan and I was in my extended Ford E-Series. After a while of doing 80 MPH I had to call her and ask to slow down. While the Honda was stable at that speed, my van felt like it was too close to its limit. I felt that an emergency like a blowout under those conditions was too risky.

[Forest Grump]

Strong wind gusts effect motorhomes. The 16,000 ford chassis does not have a track bar. Trac bars keep the axles tied to the frame and remove the sideways element of movement differences between the two.

When a gust of wind hits your coach it tips it and the coach tends to go in that direction much as counter steering does on a motorcycle, which is how you steer a motorcycle. I called safety steer about my coaches handling, much as you describe for yours. From prior experience I thought my#1 fix would be a front trac bar, they agreed. For #2 a rear track bar, they agreed. #3 front SumoSprngs to avoid the severe dips I had experience due to massive crosswinds hitting the front corners, they agreed. #4 a SuperSteer, they disagreed, I was not having tire wander. As to bigger sway bars they suggest I try 1,2 and 3 first.

Been out twice since the install. I am very pleased. Passing trucks coming or going no effect. 25 to 40 mph gusty winds in Cajon Pass we didn't know it. Leaf springs will wander. Big boxes on suspensions, um trucks and motorhomes.

[John & Diane]

Metalman, Our 2015 Windsport 27K was horrible to drive when we received it. I immediately ordered and installed a Roadmaster Reflex Stabilizer. Before taking it for test drive I discovered that all the tires were inflated to 105-110lbs. I reduced them to the 82lbs as the tag in the coach stated. With these 2 changes the handling improved so much, but still not great. After returning from a short trip I had it aligned at a truck shop. It was found to have more than 1/2" toe out where it should have had toe-in. Now it can be driven with one hand most of the time. Most passing trucks do not affect it. Now fun to drive. Good luck.

[Metalman]

Recently we were driving on I-275 in the St. Petersburg area along the Sunshine Skyway. A wind advisory sigh was posted just before the Sunshine Skyway Bridge. The wind was blasting from our right and I had to keep turning the steering wheel with quick movements to keep the RV centered in the lane. However, someone in front of us with a diesel pusher, pulling a toad was being blown half way into the lane beside him. All in all, I think our RV did well.

Unfortunately while this was going on, the foot pad on one of our leveling jacks fell off and whet skipping across the Interstate. Good ole Lippert junk.

I think I will get it aligned sometime soon, though the front tires don't appear to be wearing after about 7,000 miles that we've driven the RV.

[KNMIB]

I added a Safety-Plus and keep tires around 82 and it solved a lot of my handling problems. I did about 6000 miles out west and it was very comfortable driving, had some constant winds in western Kansas that was somewhat white knuckle but otherwise it is one hand driving

[Metalman]

I am surprised that the handling improved after you reduced the tire pressure. I filled mine to the max as written on the sidewall for less rolling resistance and less heat. I didn't see the pressure specs. on a tag in the coach. I will check the tire pressure before we take another trip.