Don't tie your dead granny to the roofracks ?
… like the Griswald family did in the classic comedy movie National Lampoon's Vacation.
For a start, it will ruin your car's handling and fuel economy.
Roof racks are good for things you don't want inside your car such as gas bottles, firewood, camping rubbish, spare fuel and smelly items like dead relatives.
But tying your dead grandmother to the roof would create too much wind drag which would reduce fuel economy and cause destabilisiation at high speeds.
Seriously though, roof racks are a great way of taking extra gear on holidays and are cheaper and more convenient than towing a trailer, but there are some issues you need to consider.
Firstly, check the load rating of your vehicle and your roof rack and never exceed them.
Roof luggage also raises the centre of gravity making your car about as stable as an upside down tenpin.
Roof luggage acts like a weight at the end of a pendulum, making the swaying motion even more pronounced.
There are some simple guidelines to packing a roof rack that will ensure that you travel safely and conveniently.
Pack light. Even though it is an ideal place to store fuel, keep this to a minimum as any liquid is heavy for its size.
Secure the load tightly. Load shift could cause your vehicle to lurch out of control. Spread the load. Too far forward and it will dive under brakes, too far back and it makes the steering light and vague.
Loading and unloading roof luggage is a real task, so it is important to pack things up there that you don't need to access often.
Remember that your car is now taller, so don't go into undercover car parks without checking the height of the vehicle or you might get a nasty surprise.
It can get wet and dusty up there, so either keep valuables inside the car or wrap them in bags that are waterproof and dustproof.
An aerodynamic pod protects your gear, prevents load shift and reduces drag thus preserving fuel economy. However, they are rigid and more difficult to pack than soft bags which are not as aerodynamic.
You should also consider what sort of roof rack you should buy.
Do you need roof rails, a rack, a pod or a variable combination?
Do you need steel or aluminium? Do you need a pod or a bag?
Light racks are only good for light loads. Stainless steel is strong and won't rust and ruin your car roof.