The definitive answer is...it depends. Very few trailers are made with axels of 2000lb (or less) capacity. Most are 2500 to 5000 llbs (per axle). So if you have a dual axle trailer with two 3500 lb axles you can haul 7000 lbs MINUS what the trailer weighs. I have a single axle 6X12 with a single 3500 lb axle. The trailer weighs approx 500 lbs, so I would feel relatively safe hauling a 3000 lb load.
A single axle utility trailer measures 12'x77" and a tandem axle utility trailer measures 16'x77". In the USA, a utility trailer can be no taller than 13 ft. 6 inches.
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Tandem by definition is two. So tandem axle is two axles. Example would be a tractor trailer having two axles next to each other is a tandem axle.
12000 pounds
60:40
A tandem truck usually refers to the amount of axles on the trailer or tractor. A single drive axle on a tractor would be referred to as a single, or the same for one axle on the trailer. I have seen it referred to the amount of tires on the end of an axle. When there are two tires on the end of the axle, that would be referred to as a dual, not a tandem.
That depends on the axle configuration. If it a closed tandem typically 17,000. If it is a spread axle 20,000. If it is a single axle (Front of a Semi) typically 12,000. Those would be the "legal weights", but states allow different amounts of weights with a permit for over weight. That all depends on the state. Wisconsin will allow 23,000 per axle.
Laws vary by jurisdiction. In the US, a trailer with a GVW in excess of 3,000 lbs. to 6,000 lbs. - dependent on state - must have an independent braking system. A tandem axle trailer would require a brake system in all states.
Depends on the truck and configuration (e.g, tandem axle dump, tractor-trailer end dump, etc.).
The average tandem axle truck can carry about 12 cubic yards of soil. Generally, a tandem axle truck has three axles.
It depends on the commercial vehicle, how it's licensed, the state it's running in, and a lot of other things, but a tractor-trailer combination with tandem axles on the tractor and the trailer can generally carry 80,000 pounds--12,000 on the front axle and 34,000 on the tractor and trailer tandems.
You need to be more specific about the configuration. Is a single axle straight truck, a tandem axle straight truck, a tandem axle straight truck with additional lift axles, a tractor trailer...?