Semis Passing Causing Motorhome To Sway

[Richardrky]

When a semi-truck is passing me my motorhome has a definite sway to the right or left depending on which side the semi is passing.
When a semi gets about 2/3 up on the left the motorhome has a definite sway to the right. I feel like it would be pushed off the rode if I didn't control it. Maybe not, but its enough to rattle my nerves. It seems I am always fighting this problem.
Does anyone know if a fix exists for this problem or do I just have to live with it.

[buck62]

First check your suspension, alignment, shocks and sway bars for wear. Is this something new or has it always existed? When I had my gas motorhome I had the same issue and went to Bilstein shocks and replaced the bushings on my sway bars, they were worn. It helps but still had the 18 wheeler sideways push. If I saw one coming up along side sometimes I would steer slightly toward it to reduce the push effect. Now I have a Diesel Pusher and it drives like a car with no sideways push at all from passing trucks but the DP also weights 34,000 pounds. The push you are feeling is due to the lighter weight of your motorhome and the heavier 18 wheeler pushing air. This is usually the first complaint a new motorhome owner has when driving. You can throw a lot of money into trying to fix it with heavy duty sway bars, steering stabilizers, shocks ect. but it boils down to physics of weight and motion.

[dezertcamper]

Sounds like your in desperate need of a rear Trac Bar. Trac bars are not cheap, but that should fix your problem. I am currently building my own trac bar system for my MH as I have the equipment available to make my own and I did not want to spend the $450 that these shops are charging for them. If I was going to buy one, the system I liked was the Blue Ox Tiger Trac bar system. Brazils Ultra trac bar looks very similar to the Blue Ox system. (Might even be the same, just a different color and name) .

If your interested in building your own you can go on OemTech's website and see his DIY page which shows you a basic setup and what is needed to make one.

Oemys Web Site - DIY Trac Bar

[Wayne M]

Yes, it happens. I will move as close to the "fog" line as possible when I notice an 18 wheeler approaching. Many of them will move to the opposite "fog" line when passing. I don't notice as much of a push as I do a drawing (sucking) motion where it tries to pull the two bodies together. Many a time the box on an 18 wheeler crosses the center line when they pass.

[scenic route]

Originally Posted by Wayne M

I don't notice as much of a push as I do a drawing (sucking) motion where it tries to pull the two bodies together. Many a time the box on an 18 wheeler crosses the center line when they pass.

As a newbie, THAT little tidbit is downright SCARY!

[GaryKD]

Hi Richardrky,
Getting your current chassis checked out is the first step. If everything is okay, the after market devices mentioned in the previous posts should be given consideration. The after market devices will lessen, but can not eliminate the push/pull one can get from passing trucks. Not knowing what is already on your coach, I would look at adding:
1. trac bar
2. rear stabilizer
3. front stabilizer
4. stiffer springs

The problem is the leaning of the coach as the truck passes. Once the coach leans to the right, the chassis will follow the weight shift. I say this because I have air suspension and installed air restrictor on my air bags. This greatly reduced the coach lean and all but eliminated the push/pull. I think your coach has a spring suspension. These restrictors will not work for you.

[Davel]

Richardrky,

I had a similar handling coach that now handles very well. The first additions were the rear track bar and the Tru-Center. They made a great difference. From having to make constant corrections, the coach now tracks very well. The Koni shocks then improved the smoothness of the ride while still maintaining great control of roll and pitching. The shocks are so smooth that most of the rattles over a series of bumps, such as railroads and tar strips, are almost nonexistant.
I purchased the Henderson Track Bar and it is very well made, but I wish I had made my own. Several people have and it is considerably cheaper. I'm going to add one to the front when we get home. I notice a very small push from the front when a semi passes that I think will go away with a front track bar.

Good luck,
Dave

[DriVer]

Originally Posted by Davel

I notice a very small push from the front when a semi passes that I think will go away with a front track bar.

Dave, I have a Tru-Trak but those folks were bought up I believe by Roadmaster. Brazel's will have a Ultra Track for the front and I would recommend it. My track bar took all the push out of the front suspension. Blue Ox has a Tiger Trak as well.

The rear track bar improved the stability of the coach dramatically. Once that was done and while going down the road I could feel the front wanting to push a little so I put on a front track bar. All the yaw problems that I previously had were all gone and it's been great over the past 4 or more years.

[Gary - K7GLD]

2 large frontal area vehicles meeting while traveling in opposite directions, with a closing speed well in excess of 100 MPH are going to create SOME reaction, unless you are driving a Sherman tank!

And if there is also a substantial crosswind added to the equation...

Sure, worn or out of adjustment steering will contribute, but I seriously doubt there is ANY common solution that will produce a hands-off stability when meeting a 18 wheeler or similar in close quarters - it just becomes a matter of percentages - a relatively light, but larger frontal-area MH IS going to get buffeted and pushed off course - and heavier ones will too - but less!

All that said, the older '88 Winnie Super Chief 27 footer we bought last fall was a real DOG in that situation, ALL over the road, and road irregularities/potholes would really create a new line of travel altogether!

All the shocks and steering stabilizer were shot, and the airbags were low on pressure - a new set of Bilstein shocks and stabilizer - and airing up the airbags all around made a HUGE difference in handling - no, doesn't by any means stick to the road like an Indy racer - but meeting a semi out on the road is no longer a trip into terror, either!

[Wayne M]

Originally Posted by scenic route

As a newbie, THAT little tidbit is downright SCARY!

It was not posted to scare anyone. It is posted as an awareness to a problem that exists. You have to be aware when an 18 wheeler, or another MH passes you that sway can, and does, happen on both vehicles. If you are zigging while he is zagging, it can get close. Most 18 wheelers will ride the fog line, as will I. The fog line is that solid white line on the outside of the lane you are in, along the shoulder.

If you think that is bad, you should tow a 40' TT without a sway bar. Even a car coming up behind you will break the draft and you will HAVE to slow down to get control. Slowing down forces the car to go around, and you have stability again. Adding a sway bar to a TT, along with Weight Distribution Hitch greatly improves that from swaying.

Drive safe.

[dieselclacker]

You should also be aware of a zone of moderate buffeting that will occur when following a Semi too closely in your motorhome. Also happens when a passing Semi truck returns to the lane in front of you a little to abruptly after making the pass.


Dieselclacker

[scenic route]

Originally Posted by Wayne M

It was not posted to scare anyone. It is posted as an awareness to a problem that exists.
Drive safe.

Duly noted...and thanks. I guess the fact that professional big rig drivers will sometimes cross into your lane took me by surprise somewhat and although I know their rigs are not on tracks, I guess I expected more from them by staying in their own lane...especially when passing. In the past, I've always been in a smaller vehicle so (although I can't recall any particular instance) if a big rig wandered into my lane, there has been a lot more room and I just never really gave it much though.

I've only had our coach on one interstate trip and I did give the 18 wheelers lots of room (I do like my mirrors) but still felt a little uncomfortable with their close proximity. I seriously doubt I'll ever get so comfortable with driving such a wide load that I'd get complacent about staying in my own lane. But knowing I COULD wander over the line and that the big rigs will occassionally do the same is scary...knock wood that it isn't toward each other...at the same time!

The 'scary factor' is probably why these collisions are somewhat rare, thankfully.

dieselclacker: Absolutely, I try to stay waaay back. I too don't like the 'pass 'n tuck' just in front of me on a pass...don't these guys know how expensive our windshields are?? Bob

[NatureCalls]

Originally Posted by dieselclacker

You should also be aware of a zone of moderate buffeting that will occur when following a Semi too closely in your motorhome. Also happens when a passing Semi truck returns to the lane in front of you a little to abruptly after making the pass.


Dieselclacker

As another newbie, I've been finding out this bit of physics all too well. Feels like my MH is pivoting in the middle! Also noticed it hates even the slightest ruts. Makes the wife scream and grab for things that aren't there.

[Chuck 1935]

A gas Motorhome is much more prone to the movement of a passing truck or side winds due to their large overhang. It is just the nature of the beast. There are many many things on the market to help correct this condition but the wheelbase problem will remain no matter how much money you throw at it. Make sure you have enough air in your tires. That will do alot to help the situation but do not exceed the max sidewall cold pressure rating.