Eliminating "Vertical Sway" or Porpoising

[W9TR]

I am towing a 2001 Coleman Mesa with a Jeep Grand Cherokee. I use a conventional 2" ball hitch with a friction sway bar and Airlift airbags on the Jeep. Sway is not an issue. The TV and trailer are properly loaded and level.

What does happen, is that, on some interstate highways, the TV and trailer get into a vertical oscillation, or porpoise. I attribute this, at least in part, to the short wheelbase of the Jeep GC. It seems that the road surface induces the problem, and it doesn't go away until I slow down.

Will a load distributing hitch fix this problem? If not, what will?

If a WDH is the answer, I think the trailer axle is at it's design load limit, or close to it. How do I calculate the additional load on the trailer axle?

Thanks!

[W9TR]

I am towing a 2001 Coleman Mesa with a Jeep Grand Cherokee. I use a conventional 2" ball hitch with a friction sway bar and Airlift airbags on the Jeep. Sway is not an issue. The TV and trailer are properly loaded and level.

What does happen, is that, on some interstate highways, the TV and trailer get into a vertical oscillation, or porpoise. I attribute this, at least in part, to the short wheelbase of the Jeep GC. It seems that the road surface induces the problem, and it doesn't go away until I slow down.

Will a load distributing hitch fix this problem? If not, what will?

If a WDH is the answer, I think the trailer axle is at it's design load limit, or close to it. How do I calculate the additional load on the trailer axle?

Thanks!

[Medorg]

If this happend to me, I would ask my mechanic to check the rear shock absorbers..they are there to prevent the continual rebounding effect.

Flagstaff Mac 205

[W9TR]

Stock shocks are OK.
Do Heavy Duty shocks offer more damping?

[Medorg]

Not necessarily, you need an expert to advise you, IMO you need a larger diameter, not a longer stroke, but repeat... see an expert.

[Dave Pelletier]

Yes a WD hitch will help as will stiffer shocks. WD hitches are adjustable. The only way to calculate the difference in axle weights would be to weigh it. Personally, I think WD hitches are more stable and safer regardless of the slight increase in axle weight.

Dave

[W9TR]

Thanks, Dave. I'll look into a WDH, as apart from changing out the TV, its probably my best bet.

[zarfus]

I know you say you are loaded properly, but you might want to get a scale out and verify that your tongue weight is high enough.... I started putting some heavy stuff to the front of my trailer and porpoising went away...

[W9TR]

You make a good point, Dan. I haven't actually measured the tounge weight. I'm assuming that with a 31 Series battery, two full propane tanks, and lots of 'stuff' in the front locker, that I'm OK. I'll measure when I get the camper out of storage this spring.