20 kg roof box + 5 kg roof rack + 55 kg payload = 80 kg total roof load.

When determining how much roof load you can carry, you need to check several things.

In the car's registration document, you will find a limit on roof load. Remember that even if the roof box is designed to withstand more weight than this limit, the value in the vehicle registration certificate must not be exceeded. You must also remember to include the weight of the rack that the roof box is attached to in the calculation.