There is a formula which can be used to accurately calculate
the position of the fifth wheel, but you need to have a few
details about the trailer and tow vehicle.
You need to know how much weight is transferred onto the
fifth wheel when laden by the trailer.
You need to know the unladen weight of the towing vehicle
and the unladen weight on each axle. You also need to know
the maximum weight allowed on each axle.
You need to know the wheelbase of the towing vehicle.
Loadbase is the distance from the fifth wheel to the front axle
The formula is
weight transferred onto front axle =
(wheelbase / loadbase)* weight transferred onto the fifth wheel
You can the play around with the "loadbase" number to achieve
the optimum weight distribution onto the front and rear axles.
Ideally you want to have weight transferred onto the front and
rear axles in the same ratio as the manufacturer's maximum gross
weights. eg max weight on steer of 3 tonnes and 6 tonnes on
the rear indicates a 1:2 ratio.
We used extensions of this basic formula to achieve maximum
loading on B Double fuel tankers with 8 compartments with
varying fuel density to ensure we max loaded to legal limts every
If you use pounds then use inches, if you use kilogrammes
use centimetres. Dont mix your avoirdupois with your metrics.
"Nehmo" <email@example.com> wrote in message
> A fifth-wheel trailer is one that has a hitch that connects to the
> towing vehicle at a point above the rear axle of the towing vehicle -
> not at a point on the rear of the vehicle as with a pull-behind trailer.
> For example, this is a 5th wheel:
> My question concerns position of the point of attachment, let's say, the
> position of the king pin. For normal pulling of the trailer, where is
> the best point to have the king pin? Should it be directly over the axle
> of the towing vehicle or should it be ahead of the axle? If ahead, by
> how much? In what ways does handling change if the position of the king
> pin is changed?
> This page http://www.etrailer.com/faq/fifthwheelfaq.asp discusses using
> a slider arrangement to move the king pin for maneuverability. It doesn'
> t discuss the optimum position for towing.
> Instructions that came with a hitch say to mount 0 to 6 inches ahead of
> the axle, but provides no further information.
> |||||||||||||||| Nehmo Sergheyev ||||||||||||||||