Glad you raised this, Tim. On my two previous travel trailers the dealer(s) installed the hitch incorrectly on one and improperly set-up the other. In both cases I had to tear apart and start from scratch. I guess my learning was to know your kit... TV, trailer and hitch. Don't trust the dealer, take the time to read the manuals and ask questions (like here ).

BTW, RAS fixed my porpoising too.

Mike

The problem with staying with the dealer settings on a hitch is that it most likely was adjusted and set up with no load. Once a rig is set up with all the permanent stuff, then loaded for a trip, the hitch will no longer be set up correctly.

Jim

Airbags do not shift mass on a truck,physics does not support it. They take some of the load off of the springs and transfer it to the axle and can stiffen the suspension. There may be a slight shift, on the order of an inch, in the center of gravity of the truck. As I said before check the GVWR and GAWR to make sure that you don't exceed them. HDPP or 3/4 ton should work well just don't overload.

If you raise the rear of the truck above level, equalizer hitch adjusted and loaded for travel you have shifting mass to the front of the truck with both bags and equalizer type hitch. Like in drag racing when suspension modifications are made to shift mass from the front to the rear at launch for increased traction, the opposite can be accomplished in towing. My truck sits loaded for towing our Imagine in its unloaded stance. This technique has shifted more mass to the front of the truck as well as having added rear suspension travel. An easy way to visualize this is to apply the technique of limits. Imagine raising the rear of the truck higher and higher until the entire mass of the truck is on its nose. With each increase in angle from back to front, more mass has been shifted to the front suspension. This is an easy way to think of the physics in applying this technique. And it works.

Jim

I surmise unloaded, loaded and loaded c/w torsion bars CAT scale tickets support this. I do know torsion bars return my front end +1/2" from a loaded unequalised stance.

Mike

Mike,
Folks with poor handling half tons can try this method or they can reject it. I don't recall guessing in setting up my truck for a near flawless towing experience, where I have not measured it in detail. Folks can speak with anyone who performs vehicle alignment to confirm the inneraction of this method to the front end of the truck. In my persuit of comfortable towing without fatigue, I realized the issue was with the light front end of the truck with its mostly aluminum powertrain and light weight sheetmetal. I changed the tires and shocks and they did help some. But not enough. Notable improvements were in leveling the rig to shift more mass to the Imagines axles, pitching the truck forward to shift mass to the front axle with aired bags and setting up the hitch after loading.
The only change I would make in doing this again would be to not use the bags with integrated jounce bumpers. The soft ride on the GMC can result in occasional contact with the integrated jounce bumpers in non-towing situations. The factory jounce bumpers were far more compliant than the integrated bumpers in the bags.

Jim

Weight distribution to the front end and tongue weight is the biggest key, assuming you are within your limits of your half ton GVWR, payload and hitch weight. Just purchased a 21G and drove it 5 hours home a couple weeks ago with a 20+ year old Reese hitch with no sway control. At the dealer before THEY connected it, hitch weight was 1000 lbs with propane and battery, winterized. While connected to the truck I added about 500lbs to the garage and all the stuff from the old camper and refrigerator items up front because I would actually like to be at 1100 lbs when completely set up. I did expect some sway and sucking because I have been here before in the past. But when I got home my hitch weight was only 840 lbs and even at just over 10% "recommended" tongue weight that was way too light. I should have weighed it myself, but I trusted the dealer that "it still looked good" and it was like 4pm. Well, every mph over 61 you knew it and 64 was tops with other trucks on the road, wife said so too so she could feel it. I ordered an Andersen hitch because I never had anything with sway control (and my Reese was 20 years old so good excuse😉) before and will be installing it tomorrow and a trip planned to NC on Christmas for a week so I will have 8.5 hours (hopefully) of drive time with the new hitch day 1 and an additional battery up front to help with the tongue weight plus some additional items upfront since we will be moving in to the camper completely.

In the towing world an absolute must is a simple Sure-Line hitch scale, they are only $140 and it is the biggest piece of knowledge money can buy. As I mentioned above assuming we are all within the parameters of the truck, it was designed to do it on its own without too much complicated bling (or any additional according to the manufacturers) but it will be close to it's limits. As long as there is enough weight on the front end by using real measurements of a tape measure of the front sag and you have enough tongue weight, over 13% it should be fine. Speaking of bling, I will be adding a rear sway bar to the truck the second week of January because I don't know why they don't even in daily driving. Since the better half and I only travel alone anymore I didn't want to go too big with TV and didn't want to go past a 1/2 ton capability because it's still my daily driver and I have already had my share of the bigger trucks and the extra costs to go with them, so I'm going to make it work even if I can't go over 65. So this next rip will consist of the Andersen hitch upgrade and additional tongue weight, better weight distribution, I'm doing it myself instead of the dealer. I can send an update early next week after it's loaded and we get there if anyone is interested. Cheers!

The Cat scale for set up in checking axle and payload limits is always good to go along with other gadgets. We are at 960lb tongue wieght fully loaded for a week long trip and with full water for our Imagine. Around 14% of trailer GVW.

Jim

I hope I can get to 14% for this trip, I honestly think that will be the magic number for my 1/2 ton and camper too as most of the time I will be without water and I will be just under 8,000, I can make it at 8,000 lbs (1120). I have a generator install planned soon so this will get more fun as I go. With full water I should be just under 9,000, but I'm not going to haul water until I have too. You can usually get that on the way close to where you are going and I want to measure to see what it does to the tongue weight. Too cold at home for that right now, I will do that in NC and I have water hook up there. Oh, my tongue weight sticker on the hitch says 1,160, even though the same hitch came on a max tow and it's rated at 1400 on it.

I noticed a lot of people that did E or D tires and air bags but the consensus seems that these 2 items provided little or no difference. E tires move around too and if memory serves me correct they also have deeper treads when new which would enhance sway when new, they can just go to 80psi to carry larger loads than we can carry. Do you agree? But, the last 1/2 ton I had was a 1992 Silverado back in the 90's so what do I know about newer half tons anyway, I've only had mine a month and a half, lol. I'm going to need tires when I get back so I will be thinking hard about that while I'm driving... (2) 115 load index light truck tires are still rated for 5,358 at 35 psi and that's still under what we are carrying with truck and hitch weight. Anyway, I'm hoping the distribution of weight on the front end and tongue weight is the main thing and a rear sway bar on the truck will be icing on the cake and some quality shocks on it down the road for a bonus with a slower rebound and she will be good. I think the stock rebound is too fast when empty to begin with, so much for FX4 off road package 🙄

I installed E rated Goodyear Endurance tires on the Imagine in place of the Westlake D rated tires. I air them up at the same recommended 65psi as the original D rated tires. The reason for this is a concern the rims cannot handle 80psi. The other is that the tire contact patch would not be optimum at 80 psi. GY has an inflation table to use for this purpose as well. Then there is ride quality on the rig as to not beat it up. The thought in doing this was to have a tire that is not at its maximum listed sidewall pressure which would make the tire more resistance to road hazard and punctures. To your point, the GY Endurance tire does not have a very deep tread so you may have something there on better sway control with respect to tread depth. GY claims this design also makes them run cooler.
I like the use of the air bags on our half ton. The bags help with the mentioned pitch of the truck as well as to increase rear suspension travel.
I also installed E rated Michelin Defender tires on the truck and while I think they are the best tire out there for a TV, I would have rather had a D rated TV tire for a little better ride quality. I air up the truck tires to 45psi front and 50 psi rear. This was done for the same reasons as for the trailer tires.

Jim

Thanks for your thoughts Jim, I installed the hitch yesterday, froze my hands off, they said it would be warmer, but... I think I may have had the chains on the Andersen a little too tight in the first connection after I watched a video that would make the back end a little too light and might make it bounce, but dang everything looked level. I didn't get to go for a test run, Mom's email "quit working" so she showed up looking for me to fix it. I'm going to start at 4 turns and work up from there if needed on the trip, it is what it is. Plus I didn't weigh my hitch and it's not completely loaded so I have no idea where the hitch weight was. Anyway I like your advice on air bags and the tires I know you have been down this road already from reading other posts. I'm sure every little bit adds up. I will get a picture of the set up when I leave somewhere more level.

For those who want to know the actual shift of the CG due to raising the rear suspension:



And an example using my trucks wheelbase. I do not know where the CG is, but here's a guess. I assumed a 4" lift:



In this semi-fictitious example, the CG only moved .8". The amount of weight transferred from the rear to the front wheels would be very small. The WDH is what transfers significant down force to the front wheels (and the trailer's wheels also). I would upload the Excel file for those who want to play, but those aren't allowed on this forum.

This problem is more complicated than a simple single point load calculation. Though distributed loads can be calculated that way, the distributed load on my truck as well as yours is unknown. So while a simple CG calculation can be performed, the actual load applied to the front of the truck is also unknown.
I'm happy you agree that there is a shift in mass to the front of the truck. A small percentage is something and that has made a difference in how my half ton handles with bags in addition to the transfer of mass from the hitch. I also believe keeping the camber on the truck in its unloaded position could have also made a positive impact in the handling of my truck. After all the truck handles best with its front alignment unchanged and that is what I have accomplished in using this setup.​​

Jim

Guest Jim - yes, it has perplexed me a bit to ascertain exactly how much force the WD hitch bars apply at their points of contact, which can then be used to calculate how much tongue weight is sent forward and to the trailer.

My EQ hitch mfr recommends (as does Ford) to try to get the front suspension back between 50 and 100% of the way to where is was before loading the hitch. Mine is at about 75%. I guess I could take some physical measurements of the front coil springs and calculate their spring constant, which in turn would give me the weight transferred to the front wheels.

Without a WD hitch, the calculations I did will easily let us know how much weight is transferred simply do to the lift. It is a small amount relative to what the WD hitch does IMO. The difficult part would be getting the CG location...

Applying the contribution from the hitch is challenging since the equalizer transfers mass to both the front of the truck and also back to the axles on the rig. One way this may be done is to evenly divide and apply the moment from the bars equallly to both the truck and rig. You may be suprised the mass transfered is rather small here as well. To your point, I have achieved 100% original height at the front and rear of the truck while loaded and ready for travel.

Jim