Gooseneck causes truck bounce?

[Chris611]

Yesterday I was bringing home a new to me 20+5 tandem single gooseneck trailer (2008 Load Max). Trailer pulled very nice. One issue though. I got on I35 south of Minneapolis and there were sections of the road that if I was going faster than 64 MPH the back of the truck would start to bounce. Bounce as is uh oh, what happened something's not right! As soon as I got my speed below 64 MPH, the bouncing stopped. I tried to drive through it once (go faster) and the bouncing got worse as the speed increased. There were other sections of the road that I was able to go 70 with no problems. Once I had the cruise set on 70 and was doing fine for 20 miles and then all of the sudden the bouncing started. Once I got into Iowa and the highway surface changed I had no problems. Any ideas on what I can change to keep this from happening? (tire pressure, etc).

Trailer was empty during all this.
Truck : '05 Chevy K2500 Duramax/Allison
Hitch : BOSS gooseneck removable ball hitch
Tires: Cooper Discoverer S/T 265/75R16 E.

Thanks
Chris

 

[MikePA]

Out of balance tires on the trailer?

 

[Patches]

seems it has something to do with the road surfaces/beds in Minn. Stay in Iowa

 

[RobS]

I had this happen on a section of I-69 east of Lansing, MI. Strangest thing. It was my fifth wheel camper and I had to slow to around 50 to avoid it. Happened both directions and I did notice at least one other rig bouncing like mine. I think the pavement surface was just right to hit the natural frequency of the truck/trailer. I haven't had that problem anywhere else.

 

[Diamondpilot]

It is the road surface. We all experience it but the Chevy/GM HD series trucks seem to be worse than the Fords and Dodges. I think it has to do with the Torsion Bar Front Suspension. It is superior in ride but there are a few trade offs. Load limit for snow plows and ride quality pulling. It will probably get better with some weight on the trailer. My neighbor pulls a 36' 5th wheel with his 2007 Dmax 3500 and he thought he made a big mistake bring it home for the first time. Once they put the aprox 2,000# of junk in the camper it rode much better.

Just be careful how you load the trailer. The GM 2500 series trucks with the Dmax only have a 8,800# GVWR. The truck weighs 7,000# so get more than 1,500# on the pin and you will have handling issues. You see a lot of GM trucks with air bags for this reason. My 2004 F-250 has 10,000# GVWR for example and my 2006 F-350 Single Rear Wheel has 11,500# GVWR.

GN's have the axles back slightly farther than 5th wheels also so a 5th wheel can get a teeter totter effect on these types of roads and will nearly flip your guts upside down.

Chris

 

[wkpoor]

Couple months ago I had the exact thing happen with a 20+4 BP on I70 east of Indy. About shook us to death on those expansion strips. It must be a combination of wheel base from rear wheel to trailer axles and distance of the strips. Last May I hauled a different trailer on the same stretch of road and didn't feel a thing.

 

[Diamondpilot]

Couple months ago I had the exact thing happen with a 20+4 BP on I70 east of Indy. About shook us to death on those expansion strips. It must be a combination of wheel base from rear wheel to trailer axles and distance of the strips. Last May I hauled a different trailer on the same stretch of road and didn't feel a thing.

We talked about that. I live just 15 miles from that stretch. I had the same issue on the same stretch pulling 5 tons on Coal on my Uncles Bri-Mar Dump trailer, about a 14,500# load with my F-350. Funny thing is my other trailers have no issue at even 75 mph upto 15,600# I thought my insides were going to explode. That section of road is concrete and its a killer.

My neighbor says he can not go over 40 in his 3500 Dmax with his 36' 5th wheel. He now just avoids it.


Chris

 

[aczlan]

Perhaps you were hitting the expansion joints like this:

What that would do is make the rear of the truck go down (just a little) and as it is bouncing back up the trailer tires are dropping into another joint. Not much, but on a trailer without shocks, it could cause the "pogo stick" effect you describe.

Aaron Z

 

[scoutcub]

Definitely the roads. I've experienced the same thing in MI, it's always in the concrete roads. Definitely gets your attention.

Very nice trailer BTW.....I have a 25+5 Loadmax gooseneck and love it!!!

 

[radman1]

Agree, it is the road and usually on cement highways. It is more noticeable with my 1999 F250 compared to my 2008 F250. My kids, when they were little, would sit in the back seat make a aahhhhh sound and let the road vibrate their voice. Kind of funny. The heavier the trailer/axles the more noticeable it is. Empty seems worse than loaded trailer. You can vary your speed sometimes to make it worse or better. Torsion axle trailers seem to do it less than spring axle.