To avoid that dreaded scraping sound and to avoid damage to your trailer, you’ll need adequate clearance from the bottom of the hitch to the ground. It’s important to note that the “drop length” of a hitch is not the same as its “total length”.
When your trailer is fully loaded, there must be a minimum clearance of 11 inches from the bottom of the hitch to the ground.
All Weigh Safe Draw Bars are 3 inches longer than their listed drop length. To ensure adequate clearance, start by using this formula to choose the right drawbar size for your adjustable trailer hitch:
Hitch Clearance Formula
Find your required drop length (use drop length formula above).
Add 3 inches.
This is your total hitch length. Subtract this number from the height of your truck’s hitch receiver (distance from the top of the inside of the hitch receiver to the ground).
This is your hitch’s amount of clearance and should be no less than 13 inches when the hitch is unloaded (uncoupled from the trailer).
Your hitch’s clearance should be no less than 11 incheswhen the hitch is loaded (coupled to the trailer and bearing tongue weight).
Here’s another example with numbers. Let’s say that you own a Ford F350 pickup truck. You’ve measured 24.5 inches from the top of your hitch receiver to the ground. You’ve considered purchasing a hitch with a 10-inch drop, for plenty of vertical height adjustment options. However, a Weigh Safe Hitch with a 8-inch drop, has a total length of 13 inches.
Using the hitch clearance formula, you calculate that 24.5 inches minus 13 inches would only leave you with 11.5 inches of clearance, unloaded. Ultimately, you decide to invest in a hitch with a drop length of no more than 8 inches, so that you’ll have plenty of clearance, especially, when your hitch is fully loaded (carrying your trailer’s tongue weight).