Big rigs are limited by federal regulation to a maximum loaded weight of 80,000 pounds including cargo, so the actual amount of cargo a big rig can carry really depends on the type and weight of the truck when empty.
But generally speaking, cargo payloads for big rigs or 18-wheelers are as follows:
- Flatbed trailers: can load up to 48,000 pounds of cargo
- Dry vans trailers: 44,000 to 45,000 pounds
- Refrigerated trailers or reefers: 42,500 to 44000 pounds.
The reason for the different payloads across the three most common trailer types is the weight of the trailer. Flatbed trailers are usually made of aluminum and as such are very light offering the highest possible payload within the 80,000-pound maximum limit. Dry vans have more to them including a fiberglass body on top of the trailer adding weight and reducing the payload by a few thousand pounds. Refrigerated trailers are even heavier than dry vans as they require insulation inside the fiberglass walls to keep freight cool or frozen plus they have to carry a massive refrigeration motor on the front of the trailer and an extra diesel tank under the trailer.
Is the 80,000-pounds spread evenly across all 18 wheels?
No, the 80,000 pounds has to be spread across all five axles but not evenly, and there are exceptions. When a big rig pulls onto a set of scales to weigh, the maximum amount over each of the three axles groups (one steer axle and two tandems) is as follows:
- Steer axle: 12,000 pounds or 6,000 pounds per tire
- Drive axle tandems: 34,000 pounds or 4,250 pounds per tire
- Trailer tandems: 34,000 pounds or 4,250 pounds per tire.
There are some exceptions including trailers that have the tandems spread apart, knowns as “spreads”. In cases where the trailer axles are 10’ 2” apart each axle can weigh 20,000 pounds on the scales allowing for the trailer axles to weigh a total of 40,000 pounds compared to 34,000 pounds for closed tandem axles. This helps when a trucker has cargo that has varying weights across its many components i.e. heavier machinery or pallets can be loaded towards the back of the trailer rather than at the front, which would cause the closed drive axle tandems to exceed the legal limit of 34,000 pounds. Of course, the maximum allowable weight is still 80,000 pounds for trucks hauling spread axle trailers.
Individual states also have additional weight carrying limits for intrastate commerce, which allow for much higher payloads based on additional axles being installed. To carry higher weights though, the truck axle specification and rating must allow for the heavier weights to be carried. These include:
- Rocky Mountain Doubles – a tractor with two trailers: a long front trailer (usually 48 feet) followed by a shorter second trailer – maximum weight up to 129,000 pounds
- Turnpike Doubles – a tractor and two long (usually 48 feet) trailers – maximum weight up to 147,000 pounds
- Triples – a tractor and three short trailers (usually 28 feet) – maximum weight up to 110,000 pounds
- Michigan Octopodes – 8-axle double trailer combinations weighing up to 164,000 pounds.
How are big rigs weighed to make sure they are legal?
Most truck stops have scales managed by a third-party and for a fee, a trucker can weigh his truck and load to see how much each axle group weighs as well as the overall weight of the big rig. Some shippers also have scales to allow trucks to weigh onsite and when on the highway, truckers have to weigh their rigs at government scale sites usually positioned at the entry and exit point of each state on the interstate highway system. State transport agencies can also set up mobile weigh scales at various locations throughout the country.
What happens if a big rig is overweight?
Current truck size and weight standards are a blend of Federal and State regulations and laws. Federal law controls maximum gross vehicle weights and axle loads on the Interstate System and if a trucker is found to be overweight both overall or on any one axle group (even if they are within the 80,000-pound gross limit), the fines can be substantial including being placed out-of-service. Overweight violations are not usually considered a criminal charge or serious enough to result in the driver’s license being canceled, but they can be costly. The amount of the fine depends on how states charge, which could be $150 for the first 3,000 pounds over the legal limit and then a further $150 for every 500 pounds over that. Each state has its own formula for fines.
How much do trucks carry on other continents and in other countries?
Truckers in Europe can load legally to 88,000 pounds and usually run 6-axle combinations with tri-axle trailers compared to their U.S. counterparts with 5-axles and 80,000 pounds.
In the outback, Australian road trains can run to 400,000 pounds gross weight spread across four trailers and as many as 88 wheels. The most common truck in Australia though is a 6-axle big rig that can have a maximum weight of 42.5 metric tonnes or 94,000 pounds. On certain roads Australian truckers have adopted the Canadian B-Train combination, which is typically a 9-axle double-trailer combination that weighs a maximum of 145,000 pounds.
Canadian weight regulations are set by each province based on the number of axles and specifications of the truck. Canadian B-Trains are 8-axle combinations with two trailers that can weigh a maximum of 140,000 pounds and in Ontario 9-axle big rigs can also gross 140,000 pounds.
The maximum weight limit in China based on new regulations established in 2016 is 36,000 pounds for two-axle trucks, 50,000 pounds for three-axle trucks, 62,000 pounds for double-steering axles and four-axle trucks, 72,000 pounds for four-axle combination vehicles, 86,000 pounds for five-axle combination vehicles and 98,000 pounds for six-axle combination vehicles.