Tail wagging

If you are pulling a vehicle you will need a trac bar. That is hopefully on my list this year. 2 years ago I put air bags on the rear of mine and that did help with the tail wagging. Most times I pull a 16' trailer with toys which weighs around 5000 lbs. I have learned to keep the tongue weight to less than 100 lbs that help me immensely with the tail wagging. As you can see in my picture I have a very short wheel base.

Please understand, I'm into Class C's and most of those are Ford E350 and E450 "van noses." For those, Ford wants at least 32% (beats me why they can't say "1/3") of loaded (truck scale) weight. You're at 31% which seems marginal at best. I'm not saying get to 33% and your worries are over. We tried to help somebody with a Class C that was in the high 20's %wise and never could get it to quit wandering. He even loaded 500# of pottery clay in the cab and it didn't help. Sold the coach. Instead of the 32% of total weight, some say the front axle should be loaded to 75% or more of its rating (GAWR). It likely works out about the same.
Based on what I've seen, done and read, I think:
1. Front axle is light
2. Rear overhang is too long or loaded too heavily
3. Rear springs and/or attaching components may be soft/loose
4. Narrow track contributes to the problem.
I still say call Henderson, Eric Davis or another specialist and be ready with a list of what you've done, the weights, your wheelbase and axle ratings.

Your front end may be to lite. Find the axle ratings, then divide the front axle rating by the rear axle rating. The ratio is the design weight ratio. Your actual ratio should be near the design ratio. With the weights given, your ratio is about 0.455. For example, on my coach, the design ratio is 0.52 and I've redistributed my loose load to maintain about 0.505. Question, does the ride improve with empty or little water in the black, gray, and FW and reduced fuel load? JM2¢...

j-d wrote:
69av is right. And from the photo there's a lot of rear overhang. you said you set tire pressures according to weight. It'd be useful to know those weights...front and rear.
What I've been thinking is you could make a test gauge. Take a couple Home Depot paint stir sticks and duct tape them to the frame so they're about an inch away from the sides of the springs but near the axle. Drive it where it misbehaves. Then see if the stix are broken torn loose or marred. If you had the stir where only the springs could reach them you have an answer.

The front weight is 4300 and the rear is 9440.It is a 15500 gvwr.

69av is right. And from the photo there's a lot of rear overhang. you said you set tire pressures according to weight. It'd be useful to know those weights...front and rear.
What I've been thinking is you could make a test gauge. Take a couple Home Depot paint stir sticks and duct tape them to the frame so they're about an inch away from the sides of the springs but near the axle. Drive it where it misbehaves. Then see if the stix are broken torn loose or marred. If you had the stir where only the springs could reach them you have an answer.

How much weight is loaded behind the rear axle. If the front end is light, it will be unstable.

You've got some Hendersons LineUp (SuperSteer) products on your coach already and done a goodly amount of work on that front axle area. The rear axle has bushings in those leaf springs and the shackles. What are those like? I wish I could find...NOPE...Just found the track bar notes I'd been thinking of

Q: My coach seems to move every which way when I steer the wheel back and forth. Is there any way to make it more stable?
A: Steering problems can manifest themselves in many different ways—and in some instances, it isn’t the steering system that’s to blame. One of the most common problems we address at Henderson’s Line-Up is an issue we call “Tail Wagging the Dog”. It’s the sensation you get when the coach seems to have a mind of its own; you steer the wheel back and forth, and the rear half steers the coach. The first coach we really experienced this on was a P32 chassis; we checked the steering gear, we tried adding stiffer springs, added a leaf on each side. It wasn’t until my brother, John, discovered that the bolts on the rear leaf spring pack had moved far enough in either direction to make contact with the adjacent spring hanger bracket. That could only mean that the axle was moving from side to side—and that was causing the loose sensation in the steering. Those early coaches only had 2-inch wide leaf springs, and they would flex. Plus, they had rubber bushings that would deflect, adding to the problem. Essentially what we did to solve the issue was create our Trac Bar, which is essentially a large Panhard bar. It is mounted horizontally at one end to the frame of the coach, and the other to the axle, creating a rigid connection that stops axle side-to-side movement. The lack of a Trac Bar, or a worn out/loose factory bar are not the only causes of Tail Wagging the Dog, but they are the most common.

Why not call the Hendersons? They seem to be the macdaddys on the RV handling scene. There's also Eric Davis at EricsRV.com who developed the front track bars for solid-axle Class A's. I'm sure there are other capable shops. One I know of is Brazel. All three are in Pacific Northwest. I've spoken with Eric Davis and he's very helpful on the phone.

I noticed you mentioned "narrow track" and see Henderson has a product for that called Spacers...

More later.

Sounds like a job for tire and axle alignment possibly.

There are 3 products designed to improve motor home handling.

TRAC BAR.. this stops tail wagging dead in it's tracks

Sway bar: Stops, or greatly reduces side to side sway (like fans at a "We Are The World" concert).

Steering stablizer.. Helps keep you on the STRAIGHT, even if it's wide.

I listed your answer first.. If it's a Ford or Workhorse, check out ULTRA POWER trac bars.