For anyone out there who knows about trailers:
Last year I bought what seemed to be a heavy-built,
double-axle trailer. While towing it home with
my Full size Chevrolet long-wheel base truck using
a 2" receiver, the trailer pushed the truck around
whenever I got above 40 mph. It seemed to 'fish-tail'.
I had no load on it whatsoever, but the tongue load
seemed higher than my other dual-axle trailer.
Would a too-heavy tongue load cause this fishtailing?
Many thanks. sdh.
That's usually symptomatic of having insufficient tongue load. You should
count on loading the trailer so that 12-15% of the total load weight is
imposed on the hitch. That should be true when the trailer is empty, too,
unless it wasn't built exactly right. A "heavily built dual-axle trailer"
reads in my book like 200-300lb on the hitch, even empty. I just bought an
18' x 7' enclosed trailer for peanuts (had a bent left-rear axle stub). It
has an empty weight of about 1200lb, and has a solid 200lb tongue weight,
empty. Even then, without a load, it tends to wander around a little behind
our 2500 van. Not bad, but a little.
You might also have a tightly sprung suspension, and be experiencing one or
both axles bouncing so badly that the tires are momentarily losing road
contact. Some trailers don't tow well empty.
Thank you very much for the information. I guess what I can
do is put a load on the front of the trailer and see if that
helps. I wasn't sure whether the fishtailing was a symptom
of front overloading or front underloading. This was a home
built trailer so it's proportions may be questionable. In
thinking about it, could it be that my hitch is higher than
it should be? That could tend to take weight off the tongue
and even raise the front axle wheels. Is that right???
Again, thanks. sdh.
The trailer tongue should be level or angled down toward
the truck. (Front of the trailer lower than the rear).
A lot of tall 4x4's don't use the proper drop receiver
and the tongue is sitting way up in the air.
I tow a travel trailer with no antisway or load levelling
and the trailer is very stable.
I was behind someone towing an empty trailer. It was
bouncing up and down. I swear I saw the truck & trailer
go perpendicular to the road heading toward the ditch.
Somehow he saved it and kept bouncing down the road.
Some tandem axle trailers will weight transfer between the axles rather
than putting load on the tongue when the tow vehicle is lower than
normal. ie when you go over a hill it will unload the hitch at the top.
Makes for a very exciting down hill run.
Unhook the trailer, let the hitch sag down to the ground. It should have
the same hitch weight as it started with. If it just hangs in the air,
you have trouble. Only way to fix is to make sure you always have at
least some load on the front, say with a big tool box that is always on
Steve Hopper wrote:
This is because there is stupid people out there making trailers that
don't know what there doing... The axles need to be 2/3's of the way to
the back of the trailer... If they are to close to the center of the
trailer they will do this and it will be a dangerous trailer to use...
Trailer stability is a complex subject, and the subject of many
old-wives tales and outright misinformation. There are a number of SAE
papers on the subject if you're up to the math. There is also a pair
of excellent books about trailers by M J. Smith (I'm not certain of
those initials) that every trailer owner should buy and read. She does
a good job of translating the technical papers into English.
Basically, every tag trailer/tow vehicle combination has a speed at
which it will become unstable. Once this speed is reached, you become
a passenger. Fortunately, things start to feel a little squeamish
slightly before that. You want the stability limit to be comfortably
higher than your planned maximum. The two most critical factors are:
distance from the tow vehicle's rear axle to the ball (smaller is
better) and the distance from the ball to the trailer axle (bigger is
better). Once the vehicles are designed, the only variables you have
are tongue weight and tire inflation. More tongue weight increases
stability through an indirect mechanism, but it's a poor substitute for
a good design. It is possible to have a trailer that is unstable even
with large tongue weights (I had one). Home built trailers seem
particularly prone to this. In such a case, the only choices are to
fabricate a tongue extension or cut it up for scrap (I did the latter),
although a really heavy tongue weight and a load-equalizing hitch might
get you by. Dual axles and their suspension (or lack of it) introduce
additional compexities as noted in this thread. I don't envy you your
choices here, but if your trailer is tossing around a long-wheelbase
pickup at 40 MPH, it's a bad one. Get rid of it before it kills you.
I bought a small trailer a few years ago that was home made and it swayed
all over the road what ever I did. I called the guy back and he had to buy
it back off me. Funny thing is he loved the trailer and regretted selling it
in the first place. I do not know how he even pulled it without swaying all
over the road.
I just bought a 3 horse slant trailer that was built one foot longer and one
foot wider. but they forgot to move the axle forward to off set the extra
weight on the tongue. The dry weight is about 3200 lb and the tongue weight
is 550 lb empty. When we hall one horse we put her in the center over the
axle. I even bought a weight dist head and bars 10,000 lb incase we ever
hall 3 horses.
My peeve with people towing trailers is that they do not have them anywhere
near level, Even the contractors. I have an adjustable receiver hitch
because I have 3 trailers at different heights and I also swap trucks that
has a different height and pull the same trailers. Great investment
(adjustable receiver hitch)
Thank you John for this valuable information. The trailer in question
is a home-built. I bought it from the estate of an old farmer and it
had probably never been used except behind a tractor. I have a feeling
that I can improve the towability of this trailer by lowering the
level at which the trailer is connected to my hitch; it think it's
too high. Again, thank you and everyone for their thoughts and
When the hitch is too high, the Center of Gravity moves back when you go
up hill. Try putting a top heavy load (like a Brdgeport or small punch
press) on something like this it will just wag at the base of a hill.
Steve Hopper wrote:
Along with the other ideas presented here, be sure to check the tire
sizes and be certain they are all the same size. Smaller tires on the
back will cause a lightness of the tongue, which will in turn cause
fishtailing. Probably not a possibility on a factory built trailer, but
if yours is homebuilt, someone may have put smaller tires on the back.
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