When you're loaded to the point where your weight will exceed your legal weight as a tandem truck. Honestly, you should probably have it lowered any time you're loaded, since a motor carrier officer who sees a tri axle, quad axle, etc. with a raised lift axle is likely to question it... even if you are legal, it's time wasted and another annoyance to deal with.
If you mean when after you get loaded, you do it while the vehicle is not in motion - don't lower your lift axle while the vehicle is moving.
96 inches for the cab, and the dump body can be up to 102 inches wide.
That depends on the dimension of the dump body. The dump body could hold 15 - 20 cubic yards of material, typically. As for what can legally be hauled, it depends on the commodity and weight of the commodity per cubic yard, as well as state laws pertaining to what weight limits they allow for a tri-axle.
20.000 - ~25,000, depending on specifics.
Concrete is measured in yards, not tons. As for permissible tonnage on a dump truck, it'll vary by state. IIRC, in North Carolina, a tri-axle dump is typically good for 16 - 18 tons, dependent on tare weight, wheelbase, and whether they're traveling on primary or secondary roads.
Depends. 17 tons, give or take, is typical.
That's going to depend on the dump truck's configuration. It could be a single axle, tandem, tri-axle, quad axle, quint axle, centipede, frameless end dump, framed end dump, etc.
They're usually between 11 - 12 feet tall at their tallest point.
Legal capacities will vary by state. In North Carolina, 16 - 17 tons was typical. In some of the northeastern states, they'll let a triaxle gross in the 70 - 72k range on secondary roads.
It's a dump truck with four axles--the steer axle in front and three axles in back. One of them moves up and down via a control in the cab, so the tires aren't on the road if the truck's not loaded. A tri-axle dump truck carries more weight than a one-axle or two-axle truck.
No. In fact, I've never operated a dump truck (or any other vehicle with a lift axle, for that matter) where the knob to raise and lower the lift axle was not in the cab.
50 000 lbs, tandem axle chassis tandem with conventional truck , 45- 46 with triaxle + truck with sleeper , 47-48 triaxle with day cab , must be under 40 000 lbs to comply with 12-34-34 per axle weigh regulation
Dump trucks come in many sizes and configurations. Additionally, vehicle weight laws vary greatly between countries. We would have to have some idea of what configuration and jurisdiction you had in mind. Configurations of dump trucks would include single axle, tandem axle, tandem axle with twin steer, tri-axle, quad axle, quint axle, centipede, tractor-trailer end dump, etc.