How many wheels does a dump truck have?

It can have anywhere from four (a small pickup with a dump body) to 22 or more (tractor and end dump trailer with lifting tag axles). For a straight truck in the US, the most wheels you'll get on a vehicle is a configuration which is known as a 'centipede' - it's a straight dump truck (10 wheels) with four lifting tag axles (8 more wheels), for a total of 18 wheels.