Rule of thumb is to not load to more than 80% of capacity
While it seems harmless to continue to load materials into a truck if it appears to have enough space, the capacity is often not what it seems. Many business owners are not aware that overloading a truck can cause premature mechanical failures and safety related problems. Mechanical failures from overloading can be severe or minor, but even minor damage can turn serious and be costly to repair if left unattended.
Overloading a truck can not only adversely affect the way it handles, stops and performs, it can cause premature wear on driveline components such as axles, suspension parts and brakes.
There are two measurements to look at when determining how much a truck can be loaded.
- GAWR – gross axle weight rating is determined for medium duty trucks by the weakest link in the truck’s suspension system, which is made up of the axle assembly, housing, springs, wheels and tires. The component with the lowest or lightest weight rating determines the GAWR. There is a GAWR for both the front and rear axles.
- GVWR – gross vehicle weight rating is determined by the sum of both the front and rear axle ratings (GAWR), or the truck’s frame or braking system. The component that has the lowest or lightest rating – either the sum of the front and rear axle or the frame or braking system – determines the truck’s GVWR.
It's generally easy to determine your truck’s GAWR and GVWR, because most vehicles display this information on a placard on the door jamb alongside tire ratings. In addition to paying close attention to both ratings when loading a vehicle, it’s also important to understand that cargo weight isn’t the only consideration when determining how much weight the truck can handle. Other key factors include how the load is positioned and weight distribution.
For example, consider a truck that has a GVWR (sum of the rear and front axle) of 25,000 pounds. The GAWR of the front axle is 7,000 pounds, and the GAWR of the rear axle is 18,000 pounds. If the truck is loaded to 23,000 pounds overall, you might think there is room for another 2,000 pounds because the overall capacity (GVWR) is 25,000. However, this may not be the case. If 20,000 pounds are loaded on the rear axle, that axle is overloaded by 2,000 pounds. The solution in this instance would be to simply reposition some of the load.
When there’s a concern that a truck may be overloaded or improperly loaded, weigh the front and rear axles individually. Compare those readings to the truck’s posted GAWR. Then add the front and rear readings to determine the gross vehicle weight and compare it to the posted GVWR of the truck. This will ensure a safe truck, keep repair and maintenance costs to a minimum, and enhance safety.
A good rule of thumb to follow is what is commonly referred to in the trucking industry as the “80%rule.” While a truck may from time to time be loaded to 100% capacity, the best practice is not to load it more than 80%. This will reduce the operating costs and help extend its service life.
The bottom line is, that overloading a truck can not only adversely affect the way it handles, stops and performs, it can cause premature wear on driveline components such as axles, suspension parts and brakes. By understanding more about a truck’s ratings and how they’re interrelated the better it will perform down the road.
Hollis Allen is the manager of Enterprise Fleet Management’s National Service Department. He works with Enterprise’s team of veteran mechanics and accredited Automotive Service Excellence (ASE) technicians to serve the fleet maintenance needs of businesses with mid-size fleets.