RE: [A/S] Re: FW: Weight equalizing hitch bars - and wheel balancing

["Oliver Filippi" <ofilippi@xxxxxxxxxxxx>]

Christopher,

You are doing fine.

There are a few minor things you should consider, but remember two wrongs do
not make a right. So I think we should first discuss the positive issues.

First the height of the hitch ball.

Since your trailer is designed for a 19.5" ball height, that is where it
should be - so that the trailer chassis is towed in an essentially level
plane to a level road (this insures that the trailer suspension is
functioning under the conditions (attitude) for which it was designed).  In
addition to the height of the ball (and the ball mount), when fully hitched
up with the spring bars adjusted for the tongue weight,  the top surface of
the ball mount should be essentially parallel to the pavement.

Some trailer gurus advocate tilting the ball mount a few degrees aft of
vertical (top slightly aft of the bottom) to compensate for the load of the
tensioned spring bar.

I don't subscribe to this logic.  I believe it should be as close to
vertical as possible (though not super critical) in order to accommodate
traversing both rises and dips.

Always remember that any adjustments to your hitch only make sense in the
contex of how the whole system will be when it is hitched, properly
adjusted, and under load.

If you have an adjustable (bolt together hitch) you can play with this angle
a little.

Assuming that you have the proper capacity spring bars, when properly
tensioned, you should end up with them more or less parallel to the trailer
chassis or a little lower to the road at the aft end.

The key thing to remember about adjusting the spring bars is to maintain the
normal attitude of the tow vehicle WITHOUT the trailer.  The best way to do
this is to first properly inflate all four tires on the tow vehicle and then
measure the height of the underside of the chassis to the ground - both
front and rear.  Then hitch up the trailer and measure the heights again.
They should both be lower (fore and aft) by about the same amount. Of course
all of these adjustments and measurements assume a smooth level area for
both trailer and tow vehicle. An unused school parking lot on a weekend is a
good option.

If you have a truck with heavy overload springs in the back (and a bed which
sticks up in the air when unloaded), you may want to compensate by using a
little less spring force, and thus carry more of the tongue weight on the
rear.  If you also carry a lot of stuff with you in the truck you may want
to load it before trying to find your ideal spring tension.

Incidentally, this is the reason a prior post (not mine) recommended weaker
hitch springs in conjunction with a higher capacity truck.  However, the
real factor has to do with the deflection properties of the rear springs
under load.  Variable rate springs will, by their very nature, deflect in a
non linear fashion with varying loads.

The long drop down bar your hitch will require (due to your tow vehicle's
chassis height) is another issue.

First, the bar should be VERY STRONG AND STIFF. You do not want any bending
in this component of the hitch. (A flimsy bar will introduce all sorts of
uncontrolled (and undesireable) motion into the hitch system.  The stiff bar
will not affect the torque applied to the receiver by the hitch spring bars.
You want to keep this as constant as possible.

There is one significant drawback to the  long drop from the receiver to the
ball mount, though.  On acceleration (or heavy load - like climbing a hill)
the offset hitch bar will put an additional torque (besides the spring bars)
on the receiver.  This will cause more downward force on the front wheels.
Likewise, under braking conditions (where the tow vehicle is doing more than
its share of the braking) or descending a  hill, there will be the opposite
effect on the receiver and an effective reduction in down force on the front
wheels.

Since the moment arm is so short relative to the length of your truck and
the truck weight, I doubt that this will be a significant factor.  However,
it does point out the need for a strong and stiff receiver, and one that is
securely mounted to the truck's frame.  This would also imply a receiver
design which has a relatively long fore and aft mount to the truck chassis.

I think you can see that the ideal hitch would be one where the receiver was
at the same height as the ball, to eliminate the torque caused by the
vertical offset between the hitch ball and the center line of the receiver.

If you have any more questions, please feel free to ask.

Oliver Filippi