A trailer has ball weight on the coupling which when connected to the vehicle is held by the suspension over the back axle. This load is redistributed to all wheels of the vehicle and trailer using a weight distribution hitch to return the vehicle to its normal height. If a load is being permanently carried in the back of the vehicle (e.g. if a toolbox has been fitted) then it may be appropriate to replace the standard springs with higher rated (carrying capacity) springs. These will not transfer any load away from the axle but will provide better support for the higher load being carried. It is preferable to transfer the ball weight when towing to ensure that the vehicle’s rear axle is not overloaded and to ensure maximum traction of all wheels on the road for optimum braking and steering control.