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Edition 47 12-13
12
On-Highway Trucks
Weight Distribution
WEIGHT DISTRIBUTION
The first step in spec’ing a Truck is to understand
how the load is distributed on the Front and Rear Axles.
The load is defined as the Maximum expected weight
of a fully loaded Truck. That includes the Driver, Fuel,
Fluids, Payload, and Truck Body. Once the axle load-
ing is known, it’s possible to begin selecting the Frame,
Engine, Transmission, Axles, Suspension, Tires, etc.
Start
by identifying where (in relation to the axles) the
load will come onto the truck. This can be a 5th wheel
location, or the center of gravity of the Body and Payload
(like a Dump Truck or Tanker). See above illustration.
Axle Loading
can be found by adding up how major
loads are distributed on each axle. Typical loads are
the weight of the Truck Chassis, Body, Payload, or 5th
wheel. Add up all the loads that apply for your Truck.
Axle Loading Due to Truck Chassis
(see “Chassis Types” tables in this section)
Front Axle Load (Given by Caterpillar) = _______ lb
Rear Axle Load (Given by Caterpillar) = _______ lb
Axle Loading Due to Body and Payload
(omit if using a 5th wheel)
Front Axle Load = (Body +Payloadweight) × (A/WB)
= _______ lb
Rear Axle Load = (Body + Payload weight) × (B/WB)
= _______ lb
Axle Loading Due to 5th Wheel
(omit if using a Body)
Front Axle Load = 5th Wheel Load × (A/WB)
= _______ lb
Rear Axle Load = 5th Wheel Load × (B/WB)
= _______ lb
Axle Loading Due to Forward Mounted Loads
(Winches, Plows, etc.)
Front Axle Load = Attachment weight × (C + WB)/
WB = _______ lb
Rear Axle Load = – Attachment weight × (C/WB) =
–_______ lb
Negative
*Max Lift Force = Lift Axle (Rated Capacity) – Weight
of the Lift Axle.
Example:
Max lift force for a 13,200 lb lift axle is approximately
12,000 lb. The remaining 1200 lb is the weight of the
axle, tires, wheels, and brakes.
Axle Loading Due to Lift Axles*
(see above illustration)
Front Axle Load = – Lift Axle Force × (E/WB) =
–______ lb
Negative
Rear Axle Load = – Lift Axle Force × (D/WB) =
–______ lb
Negative
*If more than one (1) lift axle repeat as required.
Total Axle Loading
Front Axle Load = Add all Front loads that apply =
______ lb
Rear Axle Load = Add all Rear loads that apply =
______ lb
Attachment
Weight
Center of Payload and
Body or 5th wheel location
Center of
Tandem Axle
Lift Axle Force*