What condition must be met when the front trailer supports are up and the trailer is resting on the tractor?

The condition that must be met when the front trailer supports are up and the trailer is resting on the tractor is that there is enough clearance between the tractor frame and the landing gear. This clearance is important to ensure that there is sufficient space for the landing gear to retract completely and for the trailer and tractor to function properly without any obstruction. If there isn't enough clearance, it can lead to issues such as damaging the landing gear or affecting the connection between the tractor and trailer.

Adequate clearance also helps ensure stability during transit and prevents any potential damages that could arise from contact between the trailer and tractor components. Proper alignment when connecting the trailer to the tractor is crucial for safe operation on the road.