Roof racks are a great way to carry the big, bulky items that take up too much room inside your vehicle. However, they are not designed to carry heavy weights, and if you do this you are likely to damage your vehicle and risk a serious accident. Most four wheel drives will only carry a maximum of 100kg on the roof racks. Some full length steel racks weigh around 50kg, and as a result your carrying capacity is drastically reduced. A few jerry cans and you are already looking at being over the limit. It is important to ensure that the total weight on your roof does not exceed what the manufacturer states as being the maximum.
Not all racks weigh 50kg; many don’t weigh more than 15kg. However, it does depend on the design and materials used. What is just as important as checking the maximum load your roof is designed to take, is looking at what your roof racks will carry. Some roof racks are only designed to carry 30kg each, and again these can easily be overloaded. Take note of what conditions the racks are designed to operate in as well. I have seen numerous roof racks that state ‘not for off-road’ use. If you get a set like this, put a few jerry cans up top and then travel on gravel, sand or other bumpy roads you risk damaging the racks, losing your load or damaging the roof of your vehicle.
Its all too common to see people either loading their roof racks up with more gear than what should be carried, or loading their roof’s up with more than what should be carried. Again, keep the heavy stuff inside your vehicle, and the big, bulky stuff on the racks. By doing this, you ensure that the centre of gravity is kept low, and this makes the car more stable. When you are four wheel driving, this is of extreme importance. Even when you are on the road it is much safer to have a lower centre of gravity.
The primary reason that roof racks are rated for different weights is their design and the material that is used. You will find that plastic racks generally won’t be able to carry as much as weight as steel or aluminum. Aluminum is lighter than steel, which is helpful if you want to carry heavier loads up top (again, I don’t recommend this!)