Kikki's Workshop Q&A: Let's ask Kikki ! Kikki's Workshop
Are there any dump trucks with six wheels ?
Yes, there are! Some of the big off-road dump trucks have two wheels on both sides in the back, which makes the total number of wheels six. The kind of trucks called articulate dump trucks can bend in the middle with a joint like part. They have middle wheels in addition to the ones at the front and back, which makes a total of six wheels.

Articulated dump truck HM400 (KOMATSU)