Weight & Balance
You are responsible for not being overloaded. The following are some definitions of weight you should know.
3.2.1 – Definitions You Should Know
Gross Vehicle Weight (GVW). The total weight of a single vehicle plus its load.
Gross Combination Weight (GCW). The total weight of a powered unit, plus trailer(s), plus the cargo.
Gross Vehicle Weight Rating (GVWR). The maximum GVW specified by the manufacturer for a single vehicle plus its load.
Gross Combination Weight Rating (GCWR). The maximum GCW specified by the manufacturer for a specific combination of vehicles plus its load.
Axle Weight. The weight transmitted to the ground by one axle or one set of axles.
Tire Load. The maximum safe weight a tire can carry at a specified pressure. This rating is stated on the side of each tire.
Suspension Systems. Suspension systems have a manufacturer’s weight capacity rating.
Coupling Device Capacity. Coupling devices are rated for the maximum weight they can pull and/or carry.
3.2.2 – Legal Weight Limits
You must keep weights within legal limits. States have maximums for GVWs, GCWs, and axle weights. Often, maximum axle weights are set by a bridge formula. A bridge formula permits less maximum axle weight for axles that are closer together. This is to prevent overloading bridges and roadways.
Overloading can have bad effects on steering, braking, and speed control. Overloaded trucks have to go very slowly on upgrades. Worse, they may gain too much speed on downgrades. Stopping distance increases. Brakes can fail when forced to work too hard.
During bad weather or in mountains, it may not be safe to operate at legal maximum weights. Take this into account before driving.
3.2.3 – Don’t Be Top-heavy
The height of the vehicle’s center of gravity is very important for safe handling. A high center of gravity (cargo piled up high or heavy cargo on top) means you are more likely to tip over. It is most dangerous in curves, or if you have to swerve to avoid a hazard. It is very important to distribute the cargo so it is as low as possible. Put the heaviest parts of the cargo under the lightest parts.
3.2.4 – Balance the Weight
Poor weight balance can make vehicle handling unsafe. Too much weight on the steering axle can cause hard steering. It can damage the steering axle and tires. Under-loaded front axles (caused by shifting weight too far to the rear) can make the steering axle weight too light to steer safely. Too little weight on the driving axles can cause poor traction. The drive wheels may spin easily. During bad weather, the truck may not be able to keep going. Weight that is loaded so there is a high center of gravity causes greater chance of rollover. On flat bed vehicles, there is also a greater chance that the load will shift to the side or fall off. See Figure 3.1.