Is yawing or tail wagging normal for Class A mortorhomes? How much?

Better not miss any turns then and have the gps tell me to make a uturn.  Like that will happen. ;D

That sort of see-saw motion is quite common in gas chassis coaches (except Seilerbird's). As drifter described, the huge air bow wave from a passing semi first pushes you away, and while you are fighting that, the push suddenly disappears and your pressure on your steering wheel cause you to swerve back again. And then comes the rear wake, pushing again. This is all exacerbated by the relatively long rear overhang on most gas coaches, which forms a sail that pivots you around the rear axle. Some coaches have a short wheelbase in proportion to overall length, and they will suffer more from these factors than those with a longer wheelbase. A 35 ft coach should have a chassis wheelbase of about 228" (54%), but many are much less. You can measure your wheelbase to assess how much it contributes to your problem, but that is no correction for it.

Another, smaller factor is sideways movement in the leaf spring suspension, which makes the front wheels act somewhat at odds with the steering. A track bar (panhard rod) will mostly solve that, making the coach easier to control when the sideways press is on. A similar related factor is slop in the steering, often caused by a loose fitting steering bell crank. That was common on older chassis and a replacement (Supersteer Bell Crank) usually helps. However, I think your '05 Georgie Boy already has an upgraded bell crank.

Yaw occurs when the rear end moves sideways and pushes the front end the opposite way. The track bar helps fight that motion and makes control a bit easier. Sloppy steering components (bushings, bell crank, etc) also make it it harder to control this movement.

I owned the same GB Pursuit DS as yours in a 2006 version. It was prone to being moved around by trucks passing as you describe. Attention to tire pressures helped and you do get used to it. It also helped that I kept aware of what was coming from behind (we rarely talk while driving as it takes your full attention to do it safely).

You'll be fine (and its a great rig) ;D

Ernie

As Gary brought up the pan hard bar helps. Also a Safety steer or similar helps some also I have both on mine. But the biggest difference was a front end alignment for the RV not one for the truck chassis as well as some air in the rear air bags to load the front end a bit. The other part is to understand you are driving a BIG BOX and has a lot of surface area for air to push you around as well as you sit much higher than a car/pickup/ Class "C" RV's which you will feel movement of any kind much more being so high above the wheels. 

100% normal and 100% STOPPABLE!!!!

Yes, if they wanted to they cold build them so they do not do that.  Thankfully the job can be done easily after market.

Trac Bars.. There are two versions.. Front and rear. 

Common wisdom is a REAR track bar will make the most improvement..  (I have a front one and it sure helped)

But installing track bars with stop the wag 100%  Hard. It is the part the factory left out.

Two other issues you may be able to improve on

Sway (Where the body rocks side to side like fans at a rock concert)  Improved sway bars can be fitted.

Steering stabilizers are nice too.  These assist you in keeping on the straight and narrow (And when your RV is 8'6" wide all roads are narrow)  Mine is a True Center from Blue Ox.. It is adjustable from the driver's seat.

it also has a little to do with the air displacement size and weight of a the r/v.....

any 54 foot long, 80k pound tractor trailer rig is going to dominate the airspace around any vehicle of lesser weight and mass.

a 22k pound, 35 foot long gas rig is going to be moved around a lot easier..... than the same 35 foot diesel rig that weighs half again more than a gas rig. 

the greater moving mass always wins.

John From Detroit said:

100% normal and 100% STOPPABLE!!!!

Yes, if they wanted to they cold build them so they do not do that.  Thankfully the job can be done easily after market.

Trac Bars.. There are two versions.. Front and rear. 

Common wisdom is a REAR track bar will make the most improvement..  (I have a front one and it sure helped)

But installing track bars with stop the wag 100%  Hard. It is the part the factory left out.

Two other issues you may be able to improve on

Sway (Where the body rocks side to side like fans at a rock concert)  Improved sway bars can be fitted.

Steering stabilizers are nice too.  These assist you in keeping on the straight and narrow (And when your RV is 8'6" wide all roads are narrow)  Mine is a True Center from Blue Ox.. It is adjustable from the driver's seat.

Click to expand...

My RV only had a thousand miles on it when I got it so thinking the suspension is still pretty tight.  Yes I am sure of the mileage.  It still had the original tires on it and verified via serial numbers prior to replacing them because of age.  Suppose the trac bars are not that much and will add one on the front when I get back.  Based on the feedback, what I am experiencing is normal but fixable.  If I could reduce it by 50% I would be real happy.  100%, well better just state even happier.  Unfortunately just running out of time to do it before my next trip but will post once I have it installed.  Thanks all for the feedback.  I do know that I have a new found respect on what truckers have to deal with.

Is it possible that Ford started adding a Trac Bar?  Crawled underneath and I could swear there is one there already.  If I understand it correctly, it is a pivoting bar that ties the frame and the axle together.  Attached is a picture that I took.   

Sure looks that way

My 35' on an F53 does the same, I will try that slight move to the right on next trip, good one.  I thought the expert on all things had left? 

I do agree that photo looks like a track bar.. Now one is good, two is better (one front one rear)

Common wisdom here is that the REAR is the more important trac bar..

I recall back when they first started making pickup trucks with "independent front suspension"

Now they showed it bumping over rough ground but the fact is the improvement came from the fact that IFS does not need a front track bar.  The two half axles both connect to the frame in such a way as to provide the same function.

I wonder what Seilerbird thinks about all this proven theory ! 

Ford did add a track bar to the F53, but I thought it was later than your 2005. Looks like you have one, though.

John insists that "popular wisdom" favors a rear track bar, but his is the first mention of that I have seen anywhere. I'm not convinced, since we are talking about one end vs the other of the same lever. When the back end moves one way, the front end moves the opposite way. You can stop the motion from either end. I believe that choice of front vs rear is merely a question of the easiest place to physically mount the it.

Two may indeed be better than one, though. Probably not twice as good, but better.

A track bar can only do so much. If the wheelbase is short for the overall length, you will still tend to yaw somewhat. And nothing eliminates the push-effect of the bow wave on the big slab-sided sailboat we call a motorhome. Well, nothing short of an additional 10,000 lbs of ballast! 

Thanks Gary and John.  Thought that looked like what we were discussing.  Like Gary stated, we are a large mass going down the road and will try a few of the other suggestions like moving over although not sure that couple of feet is going to make any difference except so additional safety space between us.  Thanks all at least I know this phenomenon is somewhat normal for the unit that I have.

Well back from my Sturgis 2600 mile trip and applied the suggestion of moving over when trucks were approaching.  Not sure if it was so much that or the additional weight of pulling my cargo trailer with two bikes, but the Tail Wagging although still noticeable did not seem quite as bad.  My better half said that it seemed that I was constantly correcting and my brother who helped with some of the driving said he thought the front end seemed loose.  Do not think it is loose considering the chassis only has 5,000 miles on it but scheduling a front end inspection and alignment.  Considering all of the other claimed benefits, I have also ordered one of the Steering Stabilzer-Safe-T- Plus. If that still does not do it then the rear trac bar. 

I know you can not change the laws of physics when it comes to mass because I noticed I pushed a couple RV's and trailers around myself.  Just need to get it stable enough so the better half can help with the driving!

PS: For those of you who drive the Chicago traffic everyday, my sympathy to you.

Gregg said:

Is it possible that Ford started adding a Trac Bar?  Crawled underneath and I could swear there is one there already.  If I understand it correctly, it is a pivoting bar that ties the frame and the axle together.  Attached is a picture that I took. 

Click to expand...

My Challenger on a GM chassis has a stabilizer bar half again larger than the one on yours, and the rear one was a lot bigger yet. And it's only 30 ft.  Maybe that's the problem with the 53 chassis. If it don't have anything on the rear, that's where I'd start. My Itasca didn't have anything on the rear either and it was pushed around a lot. They all don't get blown off the road, and then sucked back on but I've had some that did. I just thought they all did it, till I was test driving some for my last purchase. That was the first place I'd head was to the interstate.

On my last coach I had the extreme example of yaw due to its extreme design - Bounder 40Z tag axle. **VERY** long tail, longest I've ever seen on a coach. As a semi would pull up next to the tail, the bow wave of the truck would push the tail away, or to the right. Pushing the tail right means the nose goes left as the pivot point is the rear wheels. Then, as the semi continues to pass the bow wave moves forward and begins to push against the coach AHEAD of the rear wheels, now pushing the nose right. So, indeed, a long gas coach can experience this phenomenon, maybe some are set up to counteract this bow wave, mine certainly wasn't. Had a lot of fun in it, but it was a lot of work to drive. Regretfully, as far as I know, there is no real fix, it either wags or not (assuming the normal items, alignment, stabilizer, shocks, etc) are all good. Weird as it sounds, you will get used to it and begin to anticipate the yaw without even realizing it. 

I have 89 bounder 33 foot on p30 with a large over hang in the back . When semi pass me it was terrible, I would grip the steering wheel so tight my hands would loose feeling. I install many parts over time to help correct this and it does help. I have reduce the pushing and pulling effect by 80 percent. Before it was a safety concern now its a slight correction. Parts i have install are

Steer safe
Bilstien shocks all 4
Bilstien steering dampener
New front and rear stabilizers bushings
Firestone airbags front and rear

I still need to install the rear trac bar. I find the drive less stressful which make for an enjoyable  drive and fun camping trip

My Challenger on a GM chassis has a stabilizer bar half again larger than the one on yours, and the rear one was a lot bigger yet.

Click to expand...

Are you talking about the anti-roll (anti-sway) bars? Different thing than a panhard rod (track bar). Thickness doesn't matter for a panhard rod - it just has to be strong enough not to bend. It's not a torsion device like the anti-roll bars, where the diameter is roughly proportional to the torsion it exerts.

quadrider said:

I have 89 bounder 33 foot on p30 with a large over hang in the back . When semi pass me it was terrible, I would grip the steering wheel so tight my hands would loose feeling. I install many parts over time to help correct this and it does help. I have reduce the pushing and pulling effect by 80 percent. Before it was a safety concern now its a slight correction.

I still need to install the rear trac bar. I find the drive less stressful which make for an enjoyable  drive and fun camping trip

Click to expand...

I scratch my head on why we have to do all of this experimenting in such a mature industry.  I understand if we wanted to take things to the next level, but the companies putting these things together have engineers designing the coaches and have to be aware of the problems when road testing units.  It reminds me of Ralf Nader and the Corvair.