bounce

[SlyBones]

Most freeway surfaces rides along just fine. But there is this one freeway surface that gets the truck doing bouncing really bad. Short, fast bounce. Shakes the crap out of every thing and one in the truck.



Only when towing the trailer. I have driven this section empty with no problems. I figure that this much have something to do with setup. I was next to a Ford PS towing a similar length trailer, on same section of road and he has having no problem. His ride seemed smooth.



26' trailer at about 6500 lb, canopy and gear in back about 500 lb, and a '97 2500 4x4 at 7000 lb w/o passengers. Using typical weight distrib hitch, with sway control. 1000 bars.



Any experience in curing this?

 

[ata]

Sounds like to much Preload on your Bars back off one chain link on each side and see what happens.

 

[SlyBones]

I will try this.



Currently I am dropping only 3 links. This puts very little tension on the bars. I was wondering if maybe the problem was the other way around. Not enough load on the bars.



I have been following the instructions per the shop that sold me the hitch, bars, sway, etc. They are pretty good guys, I know them. -- However its time to double check this stuff.



I read the instructions that came with it all, last night. Says something about using enough preload on the bars so the front and rear of the truck sag the same amount, from the weight of the trailer.



Well for me this does not happen. I will go and take some measurements today. It appears that the back drops about 1. 5 - 2 inches ( with overloads this baby is stiff ). I would guess that the nose has gone up some. -- Now add tension with the bars and very little weight is shifted back to front, I am guessing the front is riding high.



Opinions wanted.

 

[ata]

The way I have set-up the hitch is take the truck to some scales and find out the front and rear axle weights. Then hook up to the trailer and adjust the Bars so the weight stays the same on the front axle and the rear axle has about 10 to 12 percent of the trailer weight on it.

So if the trucks front axle weighs 4000 and the rear axle weighs 3000 and the trailer weighs 6500 you want the rear axle to weigh 3650 to 3780 and the front axle to stay about 4000.

On the Hitch, between the drop bar and the hitch head there`s a pin with washers on it. Removing or adding one washer will change the preload on the Bars one half a chain link.

Hope this helps

 

[SlyBones]

Hmmm.....



not sure I get this, this sounds like all the tongue weight is on the back on the truck, if the front axle has no additional weight on it. so whats the point of a weight distribution hitch, if the rear is taking up all the tongue weight? Where does the weight go when the links are engaged?

 

[ata]

If you put the trailer on the truck without the Distribution Bars the weight goes on the rear axle and lifts the weight off the front axle. (frontend comes up backend goes down) When you put the Bars on it lifts the rear of the truck and puts the weight back on the front axle. So what is happening is you are pivoting the weight over the rear axle.

 

[Kirwin]

I have a similair trailer and have thought that the trailer adds just enough weight to the rear to cause it to just nicely sit on the overlad pads. Then when you hit these repetitive bumps it gets the whole thing boucing! I am considering removing the overlaod springs and going to an air bag spring. I added Blistein shocks yesterday to see if they will help. I agree that you can't effectively fix this with the weight distrubiting hitch as you don't want to add that much weight to the front axle. It is already near it's weight limit. If we had bigger trailers I don't think this would be an issue. When I put the motorcycle in the back and then hook onto the trailer the bouncing all but disappears. Hope this helps.

 

[SlyBones]

OK, so I think I got a handle on how to check the setup of the bars on the weight distrib hitch.



How should the ball height be?



I dont know how high they set it up, when I purchased it. It was done for me. The RV guy says to measure the height of the tongue of the trailer, when level, at the top there the ball would be. Add the amount the truck sags when the trailer is set on it. In this case about 2".



So if the trailer is 24", then add 2" and the ball height should be about 26" on the back of the truck unloaded. This should make it so the trailer is level when set on the truck before any weight distribution stuff is applied.



Does this sound correct?

 

[MikeBeggy]

I chased a similar gremlin during set-up of my Airstream. Proper hitch head angle, the correct size weight distribution spring bars, ball height are all factors to properly setting the towing combination. The addition of Rancho 9000s set on 5 for towing did the most for my situation after many hours of tweaking the hitch. Seems so simple now that the problem is solved.

 

[SlyBones]

I have the ranchos set for 3 front and 2 rear for normal use, and have use 3 front and 4 rear for towing use. Large bumps, etc are soaked up pretty nice. Dont have a lot of bounce problems there.



Dont know what the rear end or trailer looks like, as I have not gotten out of the truck at 60 to check. But the front end has about a 1-2 bounce that is around a 1 sec interval. You can see the front end oscillate up and down. Shakes the crap out of everything. Slowing down to about 40 makes it stop. Other freeway and road surfaces are not a problem. dont know what it is about this particular freeway surface. It can be a problem, go over a overpass where the surface changes and it will stop. Get to the other side where the main surface starts again, and it will immediately start back up. The second the road surface changes, it stops/starts, just like that.



OK, so tell me more about the hitch head angle?

 

[ata]

The top of the ball and the top of the trailer coupler should be set at the same height before hook up. So when you hook up to the truck(truck will drop 2") and then put the bars on they will pull the truck and trailer back to level. (or front of trailer slightly lower than level) A Trailer that is high in the front when hooked up is usually not stable at higher speeds or when being passed by a large truck.

The way you discribed is for setting up a trailer for not using a weight distribution hitch. So that the truck and trailer are level when hooked up.

 

[mberry]

I have the same problem with my 3500# max boat trailer. Rides like I have no shocks at all, just the axle welded to the frame. I wish I could fix it. I have never had this problem before.