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Truck drivers and fleet owners are tasked with ensuring that their vehicles are safe, reliable and compliant on U.S. roads. Part of this involves loading the truck correctly and within defined limits to avoid regulatory and liability risks as well as drivability and maintenance issues.
Whether a truck is towing or hauling cargo, it’s important to know how much weight it can safely handle before becoming overloaded, overweight and unstable. We’ve discussed everything you need to know about determining whether a truck is overloaded and what can happen if weight capacities are exceeded.
How a Truck’s Weight Is Defined
Before diving into how to determine if a truck is overloaded, it’s first important to understand some key definitions and specs related to a truck’s weight and how much it can safely carry and/or tow:
- Gross Vehicle Weight Rating (GVWR) – The maximum allowable weight of a vehicle, including a full tank of gas, topped-off fluids, cargo, passengers and accessories. This is calculated by the manufacturer and typically found on the driver’s side doorframe or in the owner’s manual.
- Gross Combined Weight Rating (GCWR) – The total weight of a loaded vehicle and its attached trailer. This value typically exceeds the GVWR because a vehicle can typically tow much more than its overall weight.
- Curb Weight – Also called the empty weight, this is how much a vehicle weighs on its own. This includes a full tank of gas and topped-off fluids, but no passengers or cargo.
- Gross Axle Weight Rating (GAWR) – The maximum weight either axle can carry individually, as limited by the weakest component in the axle system. This is specified by the manufacturer, and the front and rear axles will have different ratings.
- Trailer Tongue Weight – How much weight a trailer and its cargo exert on the truck’s tongue. This is factored into the payload capacity and ranges from 10–15% of the total trailer weight.
- Payload Capacity – The maximum weight that a truck can carry inside it.
- Towing Capacity – The maximum weight a truck can tow behind it.
It’s also important to note that the U.S. Department of Transportation groups trucks into classes ranging from 1 to 8 and categories ranging from light- to heavy-duty according to their GVWR. Knowing your truck’s GVWR and which class and category it falls into is helpful in determining its payload and towing capacities.
|
Weight Class |
GVWR |
Category |
|
Class 1 |
0–6,000 lbs. |
Light-Duty |
|
Class 2 |
6,001–10,000 lbs. |
Light-Duty |
|
Class 3 |
10,001–14,000 lbs. |
Medium-Duty |
|
Class 4 |
14,001–16,000 lbs. |
Medium-Duty |
|
Class 5 |
16,001–19,500 lbs. |
Medium-Duty |
|
Class 6 |
19,501–26,000 lbs. |
Medium-Duty |
|
Class 7 |
26,001–33,000 lbs. |
Heavy-Duty |
|
Class 8 |
33,001–80,000 lbs. |
Heavy-Duty |
What Is Considered an Overloaded Commercial Truck?
There are several factors that can contribute to a truck being characterized as overloaded. In general, a truck is considered overloaded when the payload capacity or towing capacity is exceeded. The payload and towing capacity of a truck will depend on the GVWR and curb weight, the weight of any attached trailers or truck bodies, the number of passengers and any additional items or accessories inside or on the truck. Hauling more than the maximum payload and towing capacity of your vehicle can not only cause damage to the suspension, engine, tires and more, but also creates an unsafe environment on the roadways. For this reason, the payload capacity or towing capacity of a vehicle should never be exceeded.
On a federal level, the Federal Highway Administration limits the GVWR of any single vehicle to 80,000 lbs., the weight on a single axle to 20,000 lbs., and the weight on a tandem axle group to 34,000 lbs. States can also impose their own vehicle weight limits. If these weight limits are exceeded, fines and criminal charges can result.
How to Calculate Payload and Towing Capacity for Your Vehicle
Some vehicle manufacturers may advertise the payload or towing capacity for the models they sell, but these are typically generalized and may not be accurate for the specific build of your vehicle. To ensure that you’re not overloading your vehicle and introducing risk and liability when you get on the road, you can do some simple math to determine an accurate payload and towing capacity for your truck using the specs we defined above.
Calculating Payload Capacity
You can calculate the payload capacity of your truck by subtracting the curb weight from the GVWR. The result lets you know how much you can carry inside the truck, including passengers and cargo. As an example, let’s say you drive a Class 6, medium-duty truck that has a GVWR of 26,000 lbs. and a curb weight of 15,000 lbs. The resulting payload capacity is 11,000 lbs., meaning your truck can carry 11,000 lbs. worth of passengers, tools, accessories, cargo, etc.
GVWR - Curb Weight = Payload Capacity
26,000 lbs. - 15,000 lbs. = 11,000 lbs.
If you attach a trailer to the truck, you’ll also need to subtract the trailer tongue weight from the GVWR. For our example, if the trailer weighs 10,000 pounds, the tongue weight is equal to 10% of the trailer weight, or 1,000 lbs.
GVWR - Curb Weight - Trailer Tongue Weight = Payload Capacity
26,000 lbs. - 15,000 lbs. - 1,000 lbs. = 10,000 lbs.
The weight of any other aftermarket additions that you’ve added onto your truck, such as service bodies, enclosed bodies, flatbeds, van bodies and dump bodies, will also need to be subtracted from the GVWR and curb weight to calculate an accurate payload capacity. Let’s say you’ve added a 16-foot dry freight box van onto your truck that weighs 2,500 lbs. when empty. You’ll need to subtract its weight from the GVWR as well to determine how much the truck can carry in the cab and cargo area of the van body before becoming overloaded.
GVWR - Curb Weight - Weight of Van Body = Payload Capacity
26,000 lbs. - 15,000 lbs. - 2,500 lbs. = 8,500 lbs.
Calculating Towing Capacity
To figure out the towing capacity of a truck, you’ll subtract the curb weight from the GCWR. This will not factor in anything inside the truck, other than full fluid levels, but will tell you how much weight the truck can safely tow behind it. For this example, let’s say you drive a Class 8, heavy-duty truck with a curb weight of 25,000 lbs. and a GCWR of 90,000 lbs.
GCWR - Curb Weight = Maximum Towing Capacity
90,000 lbs. - 25,000 lbs. = 65,000 lbs.
Your truck can theoretically tow up to 65,000 lbs. behind it, including the weight of the trailer and freight. However, to find out how much you can realistically tow and get an accurate towing capacity, you’ll also need to subtract the weight of any passengers, cargo inside the truck and accessories on the truck or trailer from the GCWR and curb weight as well.
What Can Happen If a Truck Is Overloaded?
The consequences of overloading a commercial vehicle can be costly. Not only are overweight vehicles and their operators subject to fines and criminal penalties, but the likelihood of dangerous crashes and damage to the vehicle increases as payload or towing capacity is exceeded.
Increased Number of Accidents
Data collected by the Federal Motor Carrier Safety Administration and the Motor Carrier Management Information System shows that Class 3–8 trucks were involved in 4,842 fatal crashes, 45,900 injury crashes and 86,618 towaway crashes in 2020, with the number of crashes increasing as the GVWR increased. From 2018 to 2020, the number of Class 3 trucks involved in fatal crashes increased 14% and the number of medium- and heavy-duty trucks involved in fatal crashes increased 19%. This data suggests that adding weight only increases the chance of a crash occurring.
Increased Stopping Distances
One of the greatest dangers of overloading a vehicle is the impact on stopping distance. Heavy-duty commercial trucks already have longer stopping distances than consumer vehicles due to their size, but when they’re improperly loaded, the extra weight can increase stopping distance even further. In these situations, drivers can misjudge the distance needed to fully brake with the excess weight, leading to potentially dangerous crashes.
Increased Maintenance and Downtime
Overloaded and overweight trucks put more stress on the truck’s suspension, axles, engine, tires, tie rods, steering arms and other drivetrain components than they’re designed to handle, leading to premature wear and irreparable damage. As weight increases, the chance of a tire blowout while driving also increases. A blown tire can cause drivers to lose control of the vehicle and potentially cause an accident, and the resulting tire debris also creates an unsafe environment for other drivers.
Even though some may think that overloading a vehicle can save time and money by increasing efficiency and reducing the number of trips, the cost of increased maintenance and downtime far outweighs any benefits.
Loss of Control and Rollover Accidents
Too much weight can also negatively impact a truck’s maneuverability and steering, making it hard for drivers to drive in a straight line, recover control after avoiding obstacles, or navigate high-traffic or tight areas. When a truck is overloaded, its center of gravity shifts and increases, which can cause the vehicle to become unstable. If the truck becomes unbalanced, the truck can potentially roll over and block roads or cause fatal accidents.
Let Rush Truck Centers Help You Find the Right Truck
As the nation’s largest commercial vehicle dealer network, Rush Truck Centers has a vast inventory of both new and used trucks in stock. Our dedicated truck sales specialists can help find a truck that’s capable of meeting the payload and towing needs of your application so that you can safely transport goods from point A to point B.
Contact or visit one of our more than 140 dealership locations across the U.S. to find a commercial truck that fits your needs.
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