Truck Bounce

[Jim_Carolyn]

I just bought a 2015 Arctic Fox 811S camper and have it mounted on a GMC Denali 3500, crew cab, 4WD with a standard box (6.5'). I also have installed air bags on the rear.

On my drive home from the dealer, I noticed that every-time I hit a rough spot in the road, the front of the truck started bouncing or as a guy at the dealer called it "Dolphining" (like a Dolphin going in and out of the water). He suspects that the air is lifting the front end of the camper slightly and therefore lifting the truck. After a couple of bounces it then stops and on smooth roads it doesn't bounce.

I had the maximum amount of air in the air bags and the rear seemed fine until I let some air out of the bags to test that then the rear started bouncing also.

I have Rancho shocks on the truck now but the dealer said maybe I should buy adjustable Rancho shocks for the front end. Another guy told me he had that problem (years ago) and bought a large air bag (like an air mattress) to fit on the top of the truck cap under the camper bed area to fill the space that exacts there - but I don't thing they make those anymore.

Has this happened to anyone else and if so how did you stop it?

Also, I tried changing my signature profile under my name but it won't take for some reason.

[Bedlam]

The scary part of new setup is that I don't feel my enclosed trailer attached to rear of the truck other than slower acceleration. I have to check my mirrors to see if it is still back there.

I was at the limits of what my F250 could handle safely. I just added 300 lbs of batteries and box to the tongue of my enclosed trailer. I would not have done this if I was keeping my 3/4t. We just returned from trip that took us over a 4000' mountain pass while loaded at almost 11,000 lbs on the rear axle. I didn't have to be so rear heavy, but it sure rode well at 22,000 lbs GCW.

[Grit_dog]

Bedlam wrote:
Hey! I resemble that remark, at least for right now. My 3/4t did the job without issue but it would not handle the triple slide TC with trailer in tow we plan in the future.

Hahaha, and what a nice truck it is!
Bottom line, if you want to make your srw short bed truck drive like it's got nothing in the bed, get a truck like Bedlam or add a combination of load carrying devices. Otherwise load er up and go. If the springs aren't sitting on the bump stops and the tires don't have pudgy cheeks, you'll get where you're going. Just don't let the bounce rock u to sleep!

[ticki2]

whizbang wrote:


For 6 years we had a 9-1/2 foot Alpenlite on a SRW F350 and we had 19.5's on the F350.

All of my issues with bounce, sway, and general bad handling came down to being overloaded. We had had 4 truck/camper combos over the years. Two were overloaded, two were not.

The properly loaded trucks drove great. The overloaded trucks staggered under the weight, despite rather expensive suspension mods.

After reading many similar threads this seems to be at the heart of the issue most of the time .

[Bedlam]

There are some good Blistien shocks available, but they are not adjustable like the Rancho's. Others have have had luck with brands that are not as popular with the truck camper crowd but are rebuildable and well known with off-roaders.

[Jim_Carolyn]

I really appreciate all your help and comments.

I have made some air pressure adjustments in the air bags and tires without it making a lot of difference.

I'm getting ready to buy the Stableloads and it looks like I can install them myself.

As for the Rancho 9000 shocks, they do not have them for my vehicle at this point (or at least not approved for my vehicle) - the vehicle is too new is what they told me on the phone. But, they are really what I want to install.

[whizbang]

No. I do not have 19.5's on a half ton.

For 6 years we had a 9-1/2 foot Alpenlite on a SRW F350 and we had 19.5's on the F350.

All of my issues with bounce, sway, and general bad handling came down to being overloaded. We had had 4 truck/camper combos over the years. Two were overloaded, two were not.

The properly loaded trucks drove great. The overloaded trucks staggered under the weight, despite rather expensive suspension mods.

[Big_Rig1]

I had a Lance 920 on my 2004 Dodge 3500 & the porpoising was mostly solved with the struts Lance sells. The struts act like a shock absorber & dampen the porpoising.

Now I have an Arctic Fox 990 (a heavier camper) on the same truck. Again I had a porpoising problem. It was not an airbag problem (don't have them), not a center of gravity problem (CG is 8 inches forward of axle).
I added adjustable Rancho shocks & set the fronts at 6 & the rears at 9. I also added the homemade equivalent of lower stableloads to engage the bottom overload spring. My upper overload springs are also engaged.
In my case the problem was solved with a stiffer suspension & shocks that would quickly dampen any porpoising that would try to start.
Seems to me porpoising is caused by not having a stiff enough suspension & shocks too weak to dampen any porpoising, the two work together, you fix these & you will solve your problem.

Big Rig (John)

[trail-explorer]

Stableloads and RS9000s will help a lot.

[deltabravo]

sabconsulting wrote:

I doubt it has anything to do with air getting underneath - more the road surface, especially if a concrete freeway which is poured in sections.

Ditto.

Also, the AF811 in short bed version, has the CG either above or slightly forward of the rear axle centerline.

jimh425 wrote:
I'm not why people are jumping on the COG bandwagon so quickly.

Ditto...

The AF811 in short bed version, has the CG either above or slightly forward of the rear axle centerline. (yes, there's an echo in here, lol)

magic43 wrote:
Springs and airbags do not stop movement. That is what shocks do. Bilsteins should work, but I installed Rancho adjustable shocks.

Ditto.

I'd lower the pressure in your airbags like others have suggested and get some Torklift Stableloads and upgrade the shocks.

Rancho 9000X shocks and Stableloads did far more to control my ride/handling than airbags ever did (in my opinion, with my truck, airbags were a waste of money.... wish I'd have tried Stableloads first).
I now only put 15 psi in my airbags most of the time, 25 if I'm towing by race trailer.

[Bedlam]

Hey! I resemble that remark, at least for right now. My 3/4t did the job without issue but it would not handle the triple slide TC with trailer in tow we plan in the future.

[Grit_dog]

billtex wrote:

mooring product wrote:


Its a short bed issue. You can slow it down but never stop it completely.

I don't understand this?

The relationship of a SB camper to SB truck is the same as a LB camper to LB truck.

Why would a SB on SB truck induce porpoising?

Please explain...

Tx, Bill

Because some people believe that anything less than a 5500 Dooley should not be hauling a heavy camper like an AF....

[Christl]

Hi: My 2009 1500 GMC bounced with the camper on with tembrins on the back axle until I installed Rancho 9000 shocks and set them to there highest setting (9) on all four shocks with 70psi in the front tires and 75psi in the back tires. With a 1/4 tank of water (approx. 10 gals) in the clean water tank situated right under the back window all bouncing disappeared. cheers christl

[Farmerjon]

billtex wrote:

whizbang wrote:
Hmmmmmmmm.

Our porpoising improved when we switched to the 19.5 tires.

You have 19.5's on a half ton?

That got my attention also.

[billtex]

whizbang wrote:
Hmmmmmmmm.

Our porpoising improved when we switched to the 19.5 tires.

You have 19.5's on a half ton?