Trailer Bounce oscillations

[ApexAZ]

Hi all,

I have some experience towing small toy trailers < 3k lbs, but never anything as big or heavy as our new toyhauler.

Is it normal to feel the back end bouncing / oscillating up and down when you go over bumps? It doesn't feel extreme, but after the initial bump, it kind of has this mild, diminishing bouncing sensation that happens 2-3 times.

We have a WD hitch that I believe I set up properly, but wondering if this is considered normal on a conventional hitch setup.

Thanks,

Brian

[Grit_dog]

Bet it tows well. I never pulled a toyhauler until this year, but have been towing dang near anything you can hook to a pickup and some that you shouldn't, since before I got my drivers license.
And the toyhauler is super predictable and stable. Partly due to over-engineered chassis (I'm at maybe 20-25% of the available payload) and partly due to axles further aft than typical TT with alot of tongue weight.

To your comment on the very stiff ride. Presume you're running 35s with a 4" lift. If you're running too high of tire pressure that will make the ride, esp over washboards and little bumps way worse.

Driving empty/bobtail. I'd be at about 50psi max Front and around 30psi rear. Look up a load v pressure chart for your size tires and base it on about 5000lbs on your front axle and around 3000lbs on rear axle when truck is not loaded with "stuff."

[ApexAZ]

My previous truck was a 15 GMC 2500 that I did just a basic cognito torsion bar level with longer UCA's and Icon shocks with external reservoir front and back. That truck rode REALLY well, but I never towed anything other than a flatbed with a SxS in back.

This truck I have a 4" CST suspension lift (4 in the front, 2 in the rear) with the Fox 2.0 pro shocks and it rides terrible compared to my 2500. Any washboard type bumps are incredibly jarring. I'm not sure if it's the shocks, the lift itself, or both. Could partly be from going to a 3500 from a 2500 too. Maybe it's just stiffer all around. It's even more stiff with the toyhauler on it, but I suppose that's to be expected when you have all that weight compressing things.

But yeah, other than the rear end oscillating up and down a few times over larger bumps, the truck seemed to handle it fine. I averaged about 63 mph, but got as high as 70 and never felt like I was fighting for control. Handling, braking and power all felt really good. The tow mode seemed to keep it in low gear going down grades and the exhaust brake really helped keep the speed under control. I feel much better after towing it a good distance. High cross-wind will be the next big test I suppose.

[Grit_dog]

Now to the contrary to what I just said, I contemplated this when hauling a truck camper. Get a set of super bad ass reservoir big diameter shocks. Find a shop that knows how to build shocks, not just rebuild them (plenty in AZ where you're from), and make a set of big heavy stout slow shocks for hauling 4000lbs in the back of a 3/4 ton. Downside is they'd be like rocks when bobtailing it.

[Grit_dog]

ApexAZ wrote:

carringb wrote:
Sound like you need more damping (aka better shocks) on the rear of the truck.

When you did the lift, I assume longer shocks were installed? The base shock on most lift kits is tuned for a softer ride, and the base shock usually is just an OEM-grade twin-tube shock. You'll see a huge improvement with a mono-tube shock, especially one spec'd for your heavier load.

Yes, they are Fox 2.0 Performance Monotube shocks.

Not clear what their load rating is. I'll see if I can find out.

The back is raised with a 2" block between the axle and the leaf springs though. Leaf springs were left alone for the lift (other than the lift block).

How they are valved is not readily available that I've found (IE compression and rebound force, damping speed, etc) however they are marketed as an "off road" shock, which can also vary greatly, IE a crawler shock is valved differently than a high speed Baja type shock.

Fox does list a different P/N between 2500 and 3500 for most applications where the shock length is presumably the same, so maybe it's a stiffer/slower action shock for a 1 ton vs a 3/4 ton.

But any shock that is valved for any off road application will likley have a soft initial compression damping and relatively quick comp and rebound characteristics. Which is opposite of the ideal shock for heavy loads/towing, where you want heavy and slow.

Like another poster here who can't seem to get "all" the "sway" out of his trailer setup, I'm not sure I'd go down any more rabbit holes with your setup.
You said it pulls good. This is one of those diminishing returns things. Less time "perfecting" the ride = more time camping and riding!

[ApexAZ]

carringb wrote:
Sound like you need more damping (aka better shocks) on the rear of the truck.

When you did the lift, I assume longer shocks were installed? The base shock on most lift kits is tuned for a softer ride, and the base shock usually is just an OEM-grade twin-tube shock. You'll see a huge improvement with a mono-tube shock, especially one spec'd for your heavier load.

Yes, they are Fox 2.0 Performance Monotube shocks.

Not clear what their load rating is. I'll see if I can find out.

The back is raised with a 2" block between the axle and the leaf springs though. Leaf springs were left alone for the lift (other than the lift block).

[carringb]

Sound like you need more damping (aka better shocks) on the rear of the truck.

When you did the lift, I assume longer shocks were installed? The base shock on most lift kits is tuned for a softer ride, and the base shock usually is just an OEM-grade twin-tube shock. You'll see a huge improvement with a mono-tube shock, especially one spec'd for your heavier load.

[ApexAZ]

Grit dog wrote:
You can simulate a little help from a suspension aid real easy.
If you have time, do this.
Cut some wood wedges or buy 4 hockey pucks or plastic felling wedges.
Insert them in your leaf pack above the bottom overload spring. So the springs get into the overload as soon as load is applied. Secure with hose clamps or even a good cinch with baling wire/tie wire.
That will stiffen your rear suspension under load.
Leave the wdh at home. Hook up and take a spin down the highway. Will give you a good idea what Stable Loads/helper springs/air bags with moderate pressure would do.
Stiffer rear springs will reduce the bounce you’re feeling.

Again, your truck is 100% capable and safe, actually ideal, for a trailer this size.

If you want send me a PM and we can talk. That trailer should pull like a dream with only minor tweaks.

Yeah, it only dropped about 2.25" in the rear when I dropped the trailer straight onto a standard ball without the WD hitch. Less than I thought it would, actually. With the WD hitch, I'm still about .75" higher than zero in the front. I was thinking I could put bags in to help raise the back another inch to try and get it closer to level. Of course I would likely have to reconfigure my hitch to drop it another inch to compensate.

We pulled it about 120 miles on Friday and it did fine. I can definitely feel it behind me, and the truck is working harder, but not a hint of sway. Even large class A's and Semi's passing me going the other direction on a 2 lane highway @ 60 mph didn't even seem to move it.

And you are right, I didn't feel any difference in steering. I actually felt pretty comfortable steering with one hand most of the way. It still has 4500 lbs to the front wheels. I have experienced that before a long time ago pulling a popup with my tacoma and the front end really felt less responsive and "floaty". Not so with this truck.

Anyway, I do feel the nose of the trailer softly bouncing the rear end a bit, but overall, the trailer was really easy to tow. Navigating tight spaces and backing up is a different story though lol.

The sherline scale measured 1750 lbs at the jack, so I'm perplexed by that. That is significantly off compared to what I had measured at the truck stop scales. I'm going to return it. But I would like something that at least gets me close enough to where I can estimate tw differences depending on how the trailer is loaded, without having to go to the cat scales every time.

[Grit_dog]

Or a simple calc will tell you how much the buggy loaded up will take off your tongue weight.

[ApexAZ]

Sjm9911 wrote:
Is it happening when your loaded up or not loaded? The toy in the back will reduce the tongue weight. When i had a pop up the porposing was either from not enough tounge weight or the trailer toung was too high. So is it level or a little bit toung down when you tow? And thats when its loaded. If you set up un loaded and add a toy it will change stuff depending on how much weight you add. So empty may need to be a bit more toung down. Also some concreate highways can cause a vibration at certian speeds, so it kind of resonates throughout. You need to change the speed when that happens to break the cycle. Play with it a bit , you'll get it better.

The weights were with it unloaded and it's a tad nose down. It's around 16% of total weight. I haven't actually loaded the SxS yet. It's currently up at the in-law's cabin. We're going to tow unloaded there and then load the General for the trip back.

Now that I have a baseline TW, my goal today before leaving is to to measure at the jack using a Sherline analog scale to figure out the % difference. Then I should be able to figure out tongue weight at the jack once it's loaded with the General. Or at least, I think that should work.

[Grit_dog]

You can simulate a little help from a suspension aid real easy.
If you have time, do this.
Cut some wood wedges or buy 4 hockey pucks or plastic felling wedges.
Insert them in your leaf pack above the bottom overload spring. So the springs get into the overload as soon as load is applied. Secure with hose clamps or even a good cinch with baling wire/tie wire.
That will stiffen your rear suspension under load.
Leave the wdh at home. Hook up and take a spin down the highway. Will give you a good idea what Stable Loads/helper springs/air bags with moderate pressure would do.
Stiffer rear springs will reduce the bounce you’re feeling.

Again, your truck is 100% capable and safe, actually ideal, for a trailer this size.

If you want send me a PM and we can talk. That trailer should pull like a dream with only minor tweaks.

[Grit_dog]

ApexAZ wrote:
Hi all,

I have some experience towing small toy trailers < 3k lbs, but never anything as big or heavy as our new toyhauler.

Is it normal to feel the back end bouncing / oscillating up and down when you go over bumps?

I'll say 100% normal. She's a big piggy, and your 1 ton springs and whatever the wdh is pulling off for weight is just fine with your truck.
Toyhaulers are (obviously) tongue heavy and axles further rearward to handle the weight of "toys."
The result is a trailer that especially with no significant weight back in the garage area, pulls very straight but also has a large cantilever from the axles to the tongue. So you're going to feel it more in the ass end of the truck. But that's why trucks have springs and shocks.

Like me, you're lifted and probably have a 6/4 lift so it's level unloaded.
Loosing a few hundred lbs off the front axle makes ZERO difference. Already got a diesel anchoring the front end and it's probably still heavier on the FA than a gas truck. I call all but guarantee the front end doesn't feel light or wander.

I installed bags, but I'm not using a wdh and I have coil spring Ram 2500 so the bare tongue weight of the trailer was dropping the back of the truck alot. Looked like the Carolina squat.
The bags not only level the truck but take out the bounce of having a significant load on the springs.

[Sjm9911]

Is it happening when your loaded up or not loaded? The toy in the back will reduce the tongue weight. When i had a pop up the porposing was either from not enough tounge weight or the trailer toung was too high. So is it level or a little bit toung down when you tow? And thats when its loaded. If you set up un loaded and add a toy it will change stuff depending on how much weight you add. So empty may need to be a bit more toung down. Also some concreate highways can cause a vibration at certian speeds, so it kind of resonates throughout. You need to change the speed when that happens to break the cycle. Play with it a bit , you'll get it better.

[ApexAZ]

theoldwizard1 wrote:
A lot depends if you have a single axle or dual axle.

Dual axle with independent suspension is supposed to be the best.

The trailer has 2 axles.

Fuel F-287
36'9"

Tow vehicle: 2020 GMC 3500 SRW standard bed with 4" lift (blocks in the rear)

I went to the scales last night and here is what I got:

Trailer was dry with the exception of 2 full 30 gal LP tanks. No toy loaded.

Trailer: 9180
TW: 1500

TV Front: 4580 (down from 4900)
TV Rear: 5440 (up from 3620)
Trailer Axle: 7680

Gross weight: 17,770

I'm not sure if a 6.5% weight reduction in the front is that concerning, but I can still do a couple things on the hitch to try and push more weight forward. I may also add some bags in the future to reduce the rear end sag a bit. The truck is lifted, so that makes it difficult to get it more level.

[theoldwizard1]

A lot depends if you have a single axle or dual axle.

Dual axle with independent suspension is supposed to be the best.