Front end bounces horribly when going over 55 mph

[tbchristian3]

Hello everyone, 

I have gone through most of the posts for cab over bouncing and I can't seem to find a solution that fits my current set up. 

I have a 2015 GMC Sierra 1500 5.3 L V8 4X4 Crew Cab.

The slide in camper is a sun lite pop up but I am not sure of the model number or exact weight. Unfortunately the guy I bought it from didn't have any info on it. He said he though it weighed roughly 1000 lbs. 

What I do know is the camper only sticks out a few inches past the tail gate so it's roughly 6ft long inside the bed. My bed is the 5.5 ft (the shortest bed they have in a 1500). I have the Happijac camper tie downs installed in between the cab and bed and tie downs mounted to the back bumper. I used a regular set of turnbuckles off of amazon. They are Brophy Machine Works brand and have a tensile strength of 2100 lbs.

The issue I am having is that when I get up to 55 mph or higher the front end of my truck starts to bounces uncontrollably. I have tried adjusting tire pressure and tightening the turnbuckles but neither of those things helped at all.  Any other pointers? is the camper to heavy for my truck? Is it a WD problem?

Here's a pic:

[Grit_dog · Accepted solution]

Not likely the issue at all. 
I feel like I asked a couple few questions you haven’t answered. As have others. 
what’s under it for suspension?

what you got for tires and pressure?

what kind of road, asphalt or concrete?

how long how far how many roads and miles have you driven it? Or any other heavily loaded truck?

I can get an almost empty truck bouncing pretty good at the right speed on the wrong concrete highway. Yet never had even a severely overloaded pickup bounce like that on smooth asphalt. Concrete panels create ridges at each panel joint where they’re saw cut, when the edges swell or curl. Sounds like what you’re experiencing, but until you provide more insight, can’t tell. 

[joerg68]

Stated weights are often very optimistic bare bones dry weights - no jacks, no battery, no propane, no water, no gear, nothing. Truck campers are notoriously heavier than you think they are, and any optimistic calculations will not help to solve your issue.

Go to a Cat scale, or try a company that has a scale (waste, sand, any place that frequently needs to weigh trucks) and ask nicely. 

What does the bouncing motion feel like? Truck camping rigs can develop a porpoising motion under the "right" circumstances, often even when under the applicable ratings. But usually not when driving on an even road.

[tbchristian3]

The bouncing is definitely in the front suspension. It feel like I am hitting bumps but the road is even, the only way it goes away is to slow way down.

[tbchristian3]

Doing some digging on the camper itself, the only model it could be with how small it is is the Sun Lite Eagle SB. The weight of that model shows 1090 LBS. With my payload capacity at 1595 LBS is this too heavy for my truck?

[mkirsch]

It's not necessarily the amount of weight, but where the weight is concentrated. On a 5.5ft bed, the rear axle of the truck is almost at the front of the bed! Most of the camper's weight is behind the axle, way behind the axle. There is no way to get weight ahead of the axle because there is no room ahead of the axle.

Use this technique which travel trailer owners use to set their weight distributing hitches: Park on a level surface. Lift the weight of the camper off the truck. Mark a spot on all four fenders centered above the wheels with a bit of tape. Measure the distance from the mark to the ground all the way around. Now lower the camper back on to the truck and measure again.

You will likely see the distance to the ground in front INcrease while the distance in the rear DEcreases. The increase up front is where your bounce is coming from.

[tbchristian3]

This sounds right, so regardless of what I do there isn't really any way to fix it? I was afraid of it being that the axle was to far forward. I understand the weight displacement from driving forklifts. I can't move the weight forward any and with the bed I have the rear axles are almost a foot closer to the cab than other regular size 1500 trucks.

[mkirsch]

You can try the other fixes suggested... tires, shocks, beefing up the suspension etc., but it really looks like a weight transfer problem to me, and none of those solutions address the weight transfer problem.

Easy way to tell would be to throw some heavy stuff on the floor in the back seat and see if it makes a difference. Got a weight set? Got some bags of sand or concrete mix?

[joerg68]

There are possibly suspension modifications that will improve the handling, but first you need to know where you are weight-wise, and if that is the likely reason for your trouble.

No modifications are free. And none of them will make the rear axle lighter (if that is indeed the issue).

Do you have LT tires on your truck?

What is the state of the shocks? You could replace them with something like Bilstein 4600.

Both would not hurt. But I have no idea if it will improve anything. There are ways to beef up the rear suspension. Some people swear by airbags. I have no advice there, except that you need to know what you do, and why you are doing it.

[tbchristian3]

I have mix use tires. Pathfinders AT. The suspensions is factory stock.

[MNtundraRet]

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@tbchristian3 wrote:

Hello everyone, 

I have gone through most of the posts for cab over bouncing and I can't seem to find a solution that fits my current set up. 

I have a 2015 GMC Sierra 1500 5.3 L V8 4X4 Crew Cab.

The slide in camper is a sun lite pop up but I am not sure of the model number or exact weight. Unfortunately the guy I bought it from didn't have any info on it. He said he though it weighed roughly 1000 lbs. 

What I do know is the camper only sticks out a few inches past the tail gate so it's roughly 6ft long inside the bed. My bed is the 5.5 ft (the shortest bed they have in a 1500). I have the Happijac camper tie downs installed in between the cab and bed and tie downs mounted to the back bumper. I used a regular set of turnbuckles off of amazon. They are Brophy Machine Works brand and have a tensile strength of 2100 lbs.

The issue I am having is that when I get up to 55 mph or higher the front end of my truck starts to bounces uncontrollably. I have tried adjusting tire pressure and tightening the turnbuckles but neither of those things helped at all.  Any other pointers? is the camper to heavy for my truck? Is it a WD problem?

Here's a pic:

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At the very least, you need to transfer more weight forward in the pickup. You may need to keep water tank and holding tanks empty when driving. Some heavy gear may need to travel in the rea seat of the truck. Other gear as far forward in the camper as possible.

[tbchristian3]

Unfortunately the camper was completely empty and I had no gear, water or anything else in the camper or truck.😬

[opnspaces]

Hi tbchristian3, welcome to the forum. I don't really know much about truck campers. But just looking at the picture it looks to me like it's ready to pop a wheelie with the slightest nudge under the front bumper.

It also looks like the camper is not snugged all the way forward to the front of the bed. Is it possible to move it forward more and make sure to transfer more weight to the front axle? Or does the bed have a curve in it and that's as far forward as it goes?

Aside from that I would do as joerg68 suggests and get the truck weights both front and back axle with the trailer installed and then again with the trailer removed. Also look inside your drivers door at the yellow and white sticker and get the max payload capacity for that particular truck.

[tbchristian3]

It seemed pretty level in person, maybe a bad picture. I also wondered if wind getting caught between the cab and the camper could be pulling it maybe? It's actually up against the bed. The gap you see is from the bed, see pic (not my actual truck).

[Grit_dog · Accepted solution]

Not likely the issue at all. 
I feel like I asked a couple few questions you haven’t answered. As have others. 
what’s under it for suspension?

what you got for tires and pressure?

what kind of road, asphalt or concrete?

how long how far how many roads and miles have you driven it? Or any other heavily loaded truck?

I can get an almost empty truck bouncing pretty good at the right speed on the wrong concrete highway. Yet never had even a severely overloaded pickup bounce like that on smooth asphalt. Concrete panels create ridges at each panel joint where they’re saw cut, when the edges swell or curl. Sounds like what you’re experiencing, but until you provide more insight, can’t tell. 

[tbchristian3]

My truck hasn't bounced at all except with this camper. I had a 25ft bumper pull camper that weighed 4890 LBS dry and it pulled with no issues with sway bars. I've also pulled a u-haul trailer with no bouncing. I think the weight distribution might be the problem. I'm not sure what you mean by the concrete panels comment?

[Cybergrunt]

I'd agree. Lose enough weight off the front axle and it will definitely impact the steering geometry and make for a very squirrelly ride.