Towball Download
Towball download is the vertical load that a coupled trailer applies to the vehicle's towball. It is also called towball mass, nose weight, or tongue weight in different markets.
A separate and shared limit
The permitted download can be limited by the vehicle, tow hitch, coupling, or trailer. Use the lowest applicable rating. It is separate from the trailer's total mass, but it normally contributes to the tow vehicle's payload and affects its rear-axle load.
Loading the trailer changes the download. Too little or too much vertical load can harm stability, steering, braking, or axle loading, so cargo placement must follow the vehicle and trailer manufacturers' instructions. A generic percentage is not a substitute for those requirements because trailer types and regional rules differ.
Check the rating for the exact variant and factory-approved towing equipment. Accessories fitted behind the rear axle and cargo already in the vehicle can further reduce the available axle and payload margin. See Towing with an Electric Vehicle for the complete towing-load calculation.