How High Should a Trailer Hitch Be?by John Garrison
Keep it Level
When trailering, your trailer should sit level. If it is too high or low, the trailer will not handle properly and will put strain on the connection between the coupler and the hitch. Also, sitting level gives the trailer the most possible road clearance.
Trucks Sag Under Weight
A truck will sag a few inches under the weight of a trailer, so you need to take this into consideration when choosing a hitch. If your truck sits 30 inches high and the trailer's coupler needs to be 20 inches high, then 8 inches of drop is suitable.
Trailer hitch ball height should be determined by first measuring the height of the hitch, and then the height of the trailer. If the trailer sits lower than the hitch, the ball mount needs to incorporate "drop." If the trailer sits higher than the hitch, then the ball mount should incorporate "rise."