For safe towing, the tongue weight must fall within 9 to 15% of total camper weight. The "optimum" load ratio is 12.5% and this number is quoted most often. Trailer Loading and Towing Guide
While the best way to do this is on a CAT scale
Find total camper weight by disconnecting your WD bars, if used, and weight the axles of the truck (front and rear) and camper's axles; then pull off the scales and disconnect the camper; then weigh just the truck (front and rear axles).
Subtract the truck weight from the combination to get total camper weight.
Add the two axles from the combined weigh; add the two axles from the disconnected weigh; and then subtract them. The difference is the true tongue weight. NOTE: this must be done without the WD bars connected or the calculation will not reflect the actual load on the truck's (or camper's for that matter) frame.
The ratio must fall between 9 and 15%. For example, an 8,000 pound travel trailer should have a 1,000 pound tongue weight for optimum handling (minimum sway and stability during braking).
Here is another way to use a bathroom scale to measure tongue weight.
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