The maximum load limit for a roof rack is listed in the vehicle specific installation instructions, or in the Fit Guide on Thule.com. This limit is determined through a CityCrash test and represents the maximum weight limit the rack can hold and maintain its position in the event of a collision. Overloading the rack will void the warranty.
The maximum load is always specified in the assembly instructions and is not to be exceeded. However, this limit is always subordinate to the maximum load recommended by the manufacturer of the car itself.
It is always the lowest value that applies.
Maximum roof load = load rack weight + any fitted rack accessories + the weight of the load itself.