Safe Weight for a Roof Box
Never exceed
the permissible gross vehicle weight as specified by the manufacturer.
Also ensure that you do not exceed the maximum roof load as prescribed
by the car manufacturer.
The safe
weight for a car roof can be affected by the width of the box and the
length of the roof bar. Below are a few examples using a roof box with
a width of 55cm.

weight
of the roof bars
+ weight
of the roof box
+ weight
of the load
=
actual
roof load |