Driving with a roof box: More storage but also more petrol used

BERLIN: Roof boxes usefully expand your car's storage space, but what do you need to know in terms of payload, speed, and petrol consumption? Here are some indicators.

One important point is that you need a base carrier that fits your car model.

A roof box should be mounted on the car using only the points intended for this purpose, according to health and safety inspection agency Tüv Süd.

This not only ensures a tight fit, but also prevents damage to the roof and its paintwork.

Eyes on maximum load

Roof boxes can't swallow an infinite amount. How much they can carry depends on the manufacturer's specifications and the maximum permissible roof load of the car.

In most cases, this is between 50kg and 100kg - a look at the car's manual will clarify this. Don't forget to take into account the weight of the box and the carrier system.

Once the roof box is safely mounted on the car you need to think about the best way to pack it. It's advisable to secure your items to stop them moving around, for example by using tension belts.

It's a good idea to put soft items such as a blanket or sleeping bag in the front of the roof box to cushion the load when the car is braking.

After driving around 50km, you should check that the box is still tightly attached to the roof, refastening it securely if necessary.

Slow down

You should also drive more slowly than normally once you have a roof box attached to the car. For one thing, the car will be more sensitive to crosswinds.

ADAC, Europe’s largest motoring association, recommends a top speed of 130kph when driving with a roof box.

Then there's the extra petrol consumption to be considered. According to ADAC, 18 per cent more petrol will be used at 130kph than without a roof box.

That adds up to an extra 1 litre per 100km, which is a good reason to remove your roof box as soon as you've finished using it.

Also, don't forget that the car now needs higher clearance if you want to avoid an unpleasant crunch somewhere like in an underground parking garage.