What Causes Fishtailing?
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Carykong
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high center of gravity can also induce sway and then fishtail. spread your load as much as possible before going up
The way I think about it is that the two tires and the hitch are the only parts of a trailer that "ground" it. These three points (the tires and the hitch) make a triangle. The whole contraption is most stable when the center of gravity is within this triangle.
One way to visualize it is to think about a square shovel sitting on the ground facing up (so that if you step on the cutting edge the handle could flip up and hit you.) Similar to a trailer, the points of contact make a triangle -- the handle, and the edge of the shovel on the ground. Now stand on the shovel anywhere inside that triangle and try to "steer" it by twisting your foot... not going anywhere. Now stand on the cutting edge (outside the triangle) and try to "steer" it -- really easy, right?
Now have a friend hold up the handle of the shovel while you do the same thing. As long as the friend can hold up your weight, they'll have a relatively easy time "steering" the shovel no matter where along the handle you stand, and you won't have much luck "steering" them. Of course if you load too close to the handle your friend will drop you, and the closer you get the more effort it will take to move the handle the same distance, because they're moving YOU farther and farther with every inch you get closer to them. Friend still holding the shovel handle, stand on the cutting edge. Now they have to press down on the handle (instead of holding up) and they'll have to fight you if you try to "steer".
Back to trailers and you add a few more dynamics. Too heavy a tongue weight can damage your tow vehicle's suspension as well as taking weight off the steering wheels, making steering light. Some tongue weight provides the stability of the weight staying inside the triangle without the disadvantages of too heavy a tongue weight. Finally, too light or negative tongue weight means you're standing on the cutting edge of the shovel, and the weight on the back of the trailer will try to steer the tongue every chance it gets. If the tow vehicle is lighter than the load, the load will steer the tow vehicle. If the tow vehicle is heavy enough to avoid being pushed, the "steering" effort doesn't just go away... it gets transferred to anything that will move -- the play in the hitch or pliability of the tires, causing the trailer to sway back and forth.
I could be wrong but that's how I think about it...
One way to visualize it is to think about a square shovel sitting on the ground facing up (so that if you step on the cutting edge the handle could flip up and hit you.) Similar to a trailer, the points of contact make a triangle -- the handle, and the edge of the shovel on the ground. Now stand on the shovel anywhere inside that triangle and try to "steer" it by twisting your foot... not going anywhere. Now stand on the cutting edge (outside the triangle) and try to "steer" it -- really easy, right?
Now have a friend hold up the handle of the shovel while you do the same thing. As long as the friend can hold up your weight, they'll have a relatively easy time "steering" the shovel no matter where along the handle you stand, and you won't have much luck "steering" them. Of course if you load too close to the handle your friend will drop you, and the closer you get the more effort it will take to move the handle the same distance, because they're moving YOU farther and farther with every inch you get closer to them. Friend still holding the shovel handle, stand on the cutting edge. Now they have to press down on the handle (instead of holding up) and they'll have to fight you if you try to "steer".
Back to trailers and you add a few more dynamics. Too heavy a tongue weight can damage your tow vehicle's suspension as well as taking weight off the steering wheels, making steering light. Some tongue weight provides the stability of the weight staying inside the triangle without the disadvantages of too heavy a tongue weight. Finally, too light or negative tongue weight means you're standing on the cutting edge of the shovel, and the weight on the back of the trailer will try to steer the tongue every chance it gets. If the tow vehicle is lighter than the load, the load will steer the tow vehicle. If the tow vehicle is heavy enough to avoid being pushed, the "steering" effort doesn't just go away... it gets transferred to anything that will move -- the play in the hitch or pliability of the tires, causing the trailer to sway back and forth.
I could be wrong but that's how I think about it...
CinderSchnauzer
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As other have said it is usually lack of weight on the tongue, however, too much weight on the tongue = light front end of the tow vehicle can cause problems as well.
Had that problem over the weekend. Unfamiliar truck / trailer. Had the tractor / snow blower pretty much over the tri axle and a box of rock fairly far forward. After experiencing some sway on the highway, we moved the rocks about 8' to the rear and the ride improved significantly.
Had that problem over the weekend. Unfamiliar truck / trailer. Had the tractor / snow blower pretty much over the tri axle and a box of rock fairly far forward. After experiencing some sway on the highway, we moved the rocks about 8' to the rear and the ride improved significantly.
Diamondpilot
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I have only had 1 boat trailer of the 10 or more that I have owned that the axles were movable. Moving the boat forward as little as 4" can make all the difference in the world. This is accomplished by moving the bow stop forward or aft to get the desired balance.
As for swaying its as others stated and loaded to tail heavy. Also, short wheel based tow vehicles are much worse than a longer based one.
Chris
bdeboer
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Did you check your tire pressures on both the truck and trailer?
jayste
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Q:What causes fishtailing?
A
ulling a 5'x8' single 3500# axle trailer, loaded with 12' 4x4's and numerous sacks of quick-crete and pulling it with a Ford Ranger! Yes, not too smart! I was trying to get by with buying my material while I was in town, after work. My pickup at the time was the Ranger and trying to build a 10'x30' front porch. Yea, I was a little light on the tongue due to trying to keep the concrete over the axles of the trailer but still had the overhang at the rear. Lesson learned and thankfully no one was injured.:thumbsup:
A
ulling a 5'x8' single 3500# axle trailer, loaded with 12' 4x4's and numerous sacks of quick-crete and pulling it with a Ford Ranger! Yes, not too smart! I was trying to get by with buying my material while I was in town, after work. My pickup at the time was the Ranger and trying to build a 10'x30' front porch. Yea, I was a little light on the tongue due to trying to keep the concrete over the axles of the trailer but still had the overhang at the rear. Lesson learned and thankfully no one was injured.:thumbsup:boggen
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have ya ever loaded down the bed of a truck to a point were the front of the truck gets real light or perhaps even lifted the front tires off the ground? it makes for harder steering.
when ya put to much weight on rear of a trailer. the trailer tires act like a teeter totor (kids playground) and it makes the rear end of the truck light. and it could be possible to get the rear tires of the pickup truck off the ground.
with rear tires light or coming off the ground. the trailer and truck. pivot at the hitch. uncontrollably, resulting in fish tailing.
when folks say keep more weight on front of trailer or more tongue weight. they are saying, put the big kid on front of trailer. and small kid on back of trailer errr teeter tottor to make it so the little kid unable to bounce the bigger kid off of the teeter totor. or rather keep the truck and trailer under control, and keep it from fish tailing.
when ya put to much weight on rear of a trailer. the trailer tires act like a teeter totor (kids playground) and it makes the rear end of the truck light. and it could be possible to get the rear tires of the pickup truck off the ground.
with rear tires light or coming off the ground. the trailer and truck. pivot at the hitch. uncontrollably, resulting in fish tailing.
when folks say keep more weight on front of trailer or more tongue weight. they are saying, put the big kid on front of trailer. and small kid on back of trailer errr teeter tottor to make it so the little kid unable to bounce the bigger kid off of the teeter totor. or rather keep the truck and trailer under control, and keep it from fish tailing.
slowzuki
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Tongue weight helps take the slack out of the connections in the ball coupling and the hitch. When there is some slack, each bump aims the tongue of the trailer side ways until the slack is used up. At that point the tires of the trailer aren't pointed in the same direction as the tow vehicle, its aimed out past, so it drives that way and then takes all the slack to the other direction, then drives back, then repeats getting sway.
Things that make it worse? Toe-out on the trailer axles, slop in the trailer suspension, slop in the tow vehicle suspension, longer overhang between rear axle of tow vehicle and hitch, shorter wheelbase of trailer, all increase how far the trailer goes before correcting its direction, making the correction more violent.
Things that make it worse? Toe-out on the trailer axles, slop in the trailer suspension, slop in the tow vehicle suspension, longer overhang between rear axle of tow vehicle and hitch, shorter wheelbase of trailer, all increase how far the trailer goes before correcting its direction, making the correction more violent.
OP
Iplayfarmer
Super Member
Not a problem in this particular situation. I have an extended cab long bed Chevy Silverado. Plenty of wheel base.
One trailer tire was low, but I aired it up where I got the hay (before the 50 mph trip home). Maybe it's time to also check the truck tires. Come to think of it, it's been a while.
I'm planning a full rebuild on this trailer including new axles, new wheel wells, and a new tongue in the very near future, so I haven't been the most diligent about maintenance of the current axles, tires, etc.