Why does my trailer jerk back and forth so much?

[rickhans]

I have a 16K gooseneck, dual axle, single wheels (all with sufficient load capacity). When loaded with my 13,500# diesel man lift, it jerks back and forth while towing extremely bad. I have the BD turnover hitch. The first time I towed it with this equipment, it did not jerk as bad. I weighed my rig on the scales to be sure I had proper weight distribution but did not have enough tongue weight according to the formulas, and I was not close to the max rear axle weight on my truck. My gross combined weight is 24,400#.



I now position it about 12" closer to the tongue which appears to sit correctly, but the jerking is terrible. I do not know if the tongue weight has anything to do with the problem but read somewhere that moving it forward should reduce the bucking.



It is not an engine problem because it continues even in neutral and coasting. It eases up on very smooth roads, which most are not in the Dallas area.



Is it my over load springs causing this? Is there any danger to lessening the tongue weight if so? Any other ideas on what is happening.



I do not have this problem when hauling my skid steer loader and equipment which totals only around 7,000#, about 1/2 of the weight of the lift.

 

[Powder Extreme]

Well, I'm sure you know you're overloaded with a 3/4 ton, but what the heck, we all do it!! You said the wheels have sufficient capacity, I'm assuming you have load range G tires. It sounds like you've got enough tongue weight your truck is sitting on the overloads which are much more "bouncy". Is one of the axles of the man lift near the back of the trailer? That can give a see saw effect of rocking back and forth on the trailer axles which of course will bounce the truck. With basically 17k in tow, I would have about 2,500lbs on the tongue. They say 20% with goosenecks and 5th wheels, but I would think 3,400 would be getting too much for a 3/4 ton. Especially when you factor in the crappy roads in Texas. The nice thing about a gooseneck is you don't have to worry about sway if you aren't loaded properly, it basically only affects the ride. I put on a set of Rancho RS9000 shocks on my truck, I couldn't believe the difference they made in ride quality, loaded and empty, might be worth a shot.



Hope this helps! Jerry

 

[Harley152]

I would first check the trailer brakes---while setting up my tt the first time I encountered the same thing--- like slow motion ABS---

was only an easy adjustment to the controller---tows like a dream now.



Jerry

 

[DMerryman]

B'Gate



Have you tried to shift some weight "port to starboard" and vise versa? I encountered a similar problem operating a different vehicle, particularly when stopping. An "off centered" weight distrbution may have a tendency to cause that trailer to buck.



Just a thought

Doug M.

 

[illflem]

I haul 26k lb loads of apples with my 3500 and can tell you from much experience that just moving the load back or forward 2 inches can make the difference between a smooth ride and getting beat up. Just try moving your load around till you find the sweet spot, then mark it on your trailer.

 

[Big John]

I also think the shocks may be a factor. The 9000's made a huge difference in my 5th wheel. The weight distribution can also make a huge difference. Like said already, 2 or 3 inches either way can make the difference.



Good Luck. John

 

[QRTRHRS]

The heavier I load my 14k, 25' beavertail, the more it beats on my truck. I usually only scale when I buy hay and then because the scale is busy, I do both truck and trailer together. Earlier this summer, the 10k I had on was worse than the 9100 lbs last week. When I load hay, I put the load on evenly, front to back. I used a smaller scale last week so did the truck and then the trailer. Of that 9100lbs, I only had 1440 on the truck. No wonder I spin in two wheel going up my driveway with a load.



My truck has an aluminum flatbed with a well to access the ball so I am kinda stuck with the ball position. I know it is forward of the axle but need to measure that distance.



Is their an optimal ball position? I have Bilstein's and Roadmasters. The Roadmasters made no difference that I could discern.

 

[CRuD]

B&W or BD

If you have the B&W I have mine sit at the forward set of holes. Puts more weight on the front of the truck. I had this trouble when I had the hitch centered over the rear axle. I moved it forward and she tows fine now. Hopes this helps.

See Ya

Chris

 

[CRuD]

Sorry what I mean by forward is as far as I could get it to the cab. Which is about 1 1/2 " forward of the rear axle. My truck and 5er pitched for and aft real bad till I moved the hitch forward.

Hope this helps. Send me a email and I will help you anyway I can.

See Ya

Chris

 

[QRTRHRS]

I took a quick peek at my ball position. Without measuring the exact distance, I would say it is about 6" forward of center. I think I heard or read that should be about right?

 

[RedRamer]

That previous suggestion about the trailer brakes might be the problem. I got a new controller and inside these things they apply more power to the trailer brakes as the stop speed increases. Something like a pendelum inside which senses the rate of stopping and the harder you stop the harder it applies the power to the triler brakes, automatically.

Maybe once you get bucking, that sensor is applying power to the trailer brakes along with the bucking motion.

Hope I make sense...

Just a thought.

 

[Bob Horrell]

My gooseneck hitch is also in a well in the middle of my aluminum flatbed. It is 2 inches forward of the axle. I have towed 20,000lbs on gooseneck without any bucking. Tongue weight was approximately 2700lbs which is light for a gooseneck. I have Rancho 9000s set on #4 for this weight, and I also have airbags which had 80lbs of air. The truck sat level with my 2 inch front lift.

With overload springs, sometimes you can get a load combination that causes the overloads to just barely come into play and this can cause a bucking as they "engage" and then "disengage". I know several people who have discarded the overloads and replaced them with airbags and solved a towing problem. Overloads are good if you carry a constant heavy load like a camper. Airbags work good when your load varies or you switch between a load and no load a lot.

I live up a very bumpy dirt load and when empty I ride on 15 to 20lbs of air on top of my springs. With the Rancho 9000s set on #3 I get a much better ride than on the stock springs. Adjustable shocks with airbags are a necessity because there is no dampening when riding empty on just the air. You need to be able to stiffen up the dampening to make the ride better.

 

[Big John]

Bob, you may be on to somethig with this comment about overloads bucking against each other. I had a 3/4ton Chebby witha 3 axle gooseneck back in the '70s that would do that very thing. I removed the overlaod springs on the 3 axles on the trailer and stopped the problem. The load would barely get on the overloads on the trailer and the truck and just beat you do death. Since this was the heaviest load I carried at the time, removing the overload springs on this particular trailer worked great. I would be careful doing it on a heavier setup without replacing the overloads with something like airbags.



I also think heavier shocks would help even in this situation.



Big John

 

[QRTRHRS]

I don't have overloads on my truck. The trailer is torsion. I have been considering either airbags or going to an airride suspension. Right now, money is a bit tight and I don't have to tow a lot so kinda holding off on doing anything. Thanks for the controller idea. Next time I tow, I am going to turn mine down for a spell.

 

[Eric_77]

Okay one thing 13. 5 on a 16k trailer is going to be overloaded no trailer with that capacity could possibly weigh 2. 5k. That said we all know and most often do overload things.



On my trailer I made a trip to Daytona last year and it was the first time ever that trailer had not bucked and bumped for me. When I went over scales I found I had almost 3. 5 k on the truck (I was at 19. 9k gross 6. 4k truck) I think that 20% rule really does work because I have a lot of bucking empty.

 

[rickhans]

Thanks for all the good responses and suggestions.



Eric_77, you left one factor out of the formula. 13,500 does not overload a 16k trailer because part of the weight is on the hitch. If I have 2,000 # on the hitch, then with the trailer weighing 3200# I only have 14,700# on the two axles which are rated at 8,000# per axle, for a total of 16,000 pounds.



I weighed my rig, although I can't find my weight tickets right now. The truck with the tongue weight was below the 8800# GVW rating, therefore my truck is not overloaded, and the trailer weighed under 16k, thus it is not overloaded. My total weight, as I recall was around 24,000 pounds. I do have G rated Hancook tube type tires that require 105#. I don't particularly like them because it is a problem backing. If I turn it too tightly, it twists the tires on the rim. I am afraid I will damage the tire and tube.



I am going to do a test with my brake controller and see if that is the problem. If not, I will re-position the lift a little further back on the trailer. I will report back the results.

 

[illflem]

B'Gate, you need to be careful with a GN since they will turn so sharp. Try to avoid sharp turns with a load or on paved surfaces as what you are saying about twisting the tires can end up as pushing them off the rims. From someone who learned the hard way.

 

[rickhans]

Is it possible to turn too sharp while going forward? I theorized that this could only happen in reverse since the trailer follows the truck going forward. i. e. you can't jacknife a trailer when pulling, only when pushing (unless sliding on ice or water). I also have never seen them twist when turning a corner. However, I watch them very close when backing.

 

[QRTRHRS]

You can jack to sharp going either way. Ever see an 18 wheeler turn so sharp that one set of wheels actually turns in the oposite direction? You could do the same with your trailer. Some times the brain does not work but I allways try to plan ahead when I set up to load. Better to do your jacking around empty if that is the situation at hand.

 

[rickhans]

I towed my man-lift today. Adjusting the brake controller did not affect it, but how I load it seems to. The bucking was not as bad today. I am going to move it a few more inches back and probably that will take care of the problem.



I found my weight tickets. I was slightly over on the truck, weighing in at 4240 on front axle, and 4940 on the rear axle, for a total of 9180. I had a lot of tools and stuff that added the weight. The trailer axles weighed in at 15,600#, just 400 under gross, for a total of 24780 pounds. The truck is rated at 8880 and 16k on the trailer which means I am 100 pounds under the max. legal combined weight.