Tongue weight is the downward force exerted on the hitch ball by the trailer coupler with weight-distributing devices, if any, deactivated.
Tongue weight should be approximately 10% to 15% of the total weight of the trailer.Generally, more is better, but much more than 15% may actually increase the likelihood of sway, especially if the tongue weight approaches or exceeds the tongue weight rating of the tow vehicle. Note that this applies to pop-ups, travel trailers, and utility trailers. Fifth wheels often run at 25-30% tongue weight (because the tow vehicle can take it), and tractor-trailers average near 50% tongue weight.
Measuring Tongue Weight
It is possible to measure the tongue weight of a loaded trailer by using bathroom scales.
Tongue weight can be adjusted through simple packing/loading techniques. Moving items in the trailer forward will increase the tongue weight, whilst moving items to the rear of the trailer will decrease the tongue weight.
Adding extra items to the rear half of the trailer will also lighten the tongue weight.
Up to 250 lbs can be measured using bathroom scales. The trailer should be fully loaded and level for this exercise.
Place the household scale and a small block of wood as high as the scale 3 feet apart (see diagram). Re-zero the scale to correct for the weight of the wooden beam and trailer tongue support. Make sure the trailer wheels are blocked securely and rest the trailer coupler on the beam on foot from the small block of wood and 2 feet from the scale.
Simply multiply the scale reading by 3 to give you your tongue weight.