Driving a large, heavy duty commercial motor vehicle requires a certain measure of skill and professionalism. Expert truck drivers need to be well-versed in a number of different things, from safe driving techniques, to their CSA scores to proper weight distribution.
Sure, weight distribution sounds like a dry and boring topic, but it is hugely important in ensuring the safety of not only the cargo you are hauling, but of your safety and those around you. There are also specific weight distribution requirements that you should always know. Let’s dig a little deeper.
Principles of Weight Distribution
There are several aspects of weight distribution.
- Gross Vehicle Weight (GVW): The total weight of the vehicle, plus its load.
- Gross Combination Weight (GCW): The total weight of the powered unit, plus the trailer and load.
- Gross Vehicle Weight Rating (GVWR): The value that a manufacturer specifies as the loaded weight of a single vehicle.
- Gross Vehicle Combination Weight Rating (GCWR): The value the manufacturer specifies as the loaded weight of a combination motor vehicle.
- Axle Weight: The amount of gross weight that rests on a given axle.
- Tire Load: The maximum weight a tire can carry when inflated to a specified pressure.
- Coupling Device Capacity: Coupling devices carry a rating that states the maximum weight they can pull or carry.
All of these aspects are governed by specific legal weight limits. For more information on the weight limit, or the formula used, see CFR 658.17. At all times, the maximum GVW should be 80,000 lbs.
The maximum gross weight on any one axle should never exceed 20,000 lbs. This also includes a grouping of axles, if required. The maximum gross weight on a tandem axle is 34,000 lbs.
If a vehicle is over the Bridge Gross Weight Formula, it is not allowed on interstate highways. The formula we linked to previously limits the weight on groups of axles in effort to ensure highways and bridges aren’t damaged.
Risks of Overloading
Overloading is a serious problem and can’t be overlooked in a discussion surrounding weight distribution. Overloading a vehicle can seriously inhibit steering, braking and speed control.
A vehicle that is overloaded will move slowly on upgrades and gain far too much speed on downgrades. Stopping distance is increased dramatically and brakes can fail if they are overworked.
Sometimes, you should even be wary of maximum weight, depending on your route. If you are driving through bad weather or a very hilly, mountainous area, it may not be safe to even operate at maximum weight, let alone overloaded.
Top-heavy loads also raise your risk. A high center of gravity increases the chances that your vehicle could tip over. Top-heavy loads are also dangerous when you have to swerve to avoid a hazard or navigate a particularly windy stretch of road. Always load your cargo so that it is heaviest on bottom and lightest on top.
The fact is this: Poor weight distribution can make a vehicle unsafe. It can jeopardize both your cargo, your vehicle and those around you. Too much weight on your steering axle can cause hard steering and potentially damage your steering axle or tires. It could also negatively impact vehicle handling and speed control.
Conversely, underloaded axles can make the weight on the steering axle too light for you to steer safely. Too little weight on drive axles can increase the risk of poor traction and potential hydroplaning. You may find your drive wheel spinning way too easily.
As a professional truck driver, proper weight distribution and cargo handling are two of the most important aspects of the job. Are you prepared for a safe ride on the road?