Tongue Weight (TW)
WARNING: This page is about a different car, the 2009 Dodge Caliber. However, it is still accessible from the selected car via links, so may be relevant.
The tongue weight is the downward force exerted on the hitch ball by the trailer. In most cases, it should not be less than 7% or more than 10% of the trailer load. Trailer tongue weight must not exceed the lesser of either the hitch certification rating, or the trailer tongue chassis rating. It should never be less than 4% of the trailer load, and not less than 55 lbs (25 kg). You must consider tongue load as part of the load on your vehicle and its GAWR.
WARNING:
An improperly adjusted hitch system may reduce handling, stability and braking performance and could result in an accident. Consult with your hitch and trailer manufacturer or a reputable trailer / caravan dealer for additional information. Failure to follow these instructions may result in possible serious or fatal injury.