Professional Driver's Handbook


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About loads and loading

Weight distribution

The weight distribution of cargo has a definite bearing on the handling characteristics of the vehicle, as well as the life of the tires, frame, springs, axles and bearings.

Even though the total load may not be over the total carrying capacity of the vehicles, poor distribution of weight could be overloading an axle or set of tires. Undue stress could be placed on the frame resulting in permanent damage and steering misalignment.

Distribution of weight will depend on the nature of the load. The loading of one piece of cargo which comprises the full load will present different problems from a load made up of a number of pieces of cargo.

Weight distribution

Correct

This loading distributes an equal weight on all rear tires and eliminates twisting and stress on the frame. Uniform crosswise loading also prevents axle housing and wheel bearing overloading.

Weight distribution

Incorrect

A very heavy load should not be loaded on one side. This overloads one spring and the tires on that side. This loading could be bad enough to allow the brakes to lock on the wheels on the light side and cause flat spots on the tires or a skid on a wet surface.


Weight distribution

Correct

The proper place for the concentrated load illustrated is just ahead of the rear axle with the longest side on the floor.

Weight distribution

Incorrect

This type of loading never should be permitted. The frame bends, the rear tires are very much overloaded and enough weight is taken from the front tires to make steering almost impossible.


Weight distribution

Correct

A tractor-trailer combination is the proper vehicle for use in service like this. By using the proper vehicle, damage to the truck and tires, and even serious collisions, may be avoided.

Weight distribution

Incorrect

This type of loading results from the use of the wrong vehicle for the job. On rough roads, such loading can result in an actual pivoting of the truck on its rear wheels, taking the front wheels entirely off the road.

Approximate distribution of total weight - vehicle plus payload

Trailers are designed for uniform load distribution, as shown previously. The fundamental difference between loading trailers and trucks is: in the case of trucks, the average design provides for about 90% of the payload on the rear tires and 10% on the front tires. In the case of a trailer, the payload should be distributed equally between the rear tires and the fifth-wheel which transfers its load to the tractor unit.

Vehicle plus payload

Vehicle plus payload

Incorrect

A very heavy load should not be loaded on one side. This overloads one spring and the tires on that side. This loading could be bad enough to allow the brakes to lock on the wheels on the light side and cause flat spots on the tires or a skid on a wet surface.


The load should be centred to give the proper wheel load distribution. The average single unit truck has a central weight distribution point midway between the rear of the cab and the tailgate. The average semi trailer type truck has a central weight distribution point at approximately the middle of the trailer.

Disclaimer

Rev: 2017