Q: Which wheels get power in an 18-wheeler?

asked by on February 17, 2017

Which wheels are powered by the engine in an 18-wheeler? Or realistically just the semi portion, the front 6? The rear 8?

Hi there. The term "18-wheeler" is kind of misleading. The typical heavy duty semi/trailer combination has a tire configuration like this: The front two tires are responsible for steering and braking. The next set of (8) tires on the semi-truck itself are what are known as the drive tires or "twin screws". Each of the (2) axles has (4) tires each and is responsible for power application from the engine to the ground. The trailer portion of the "18-wheeler" has another (8) tires on (2) axles, but are "floating" tires; with brakes.

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