Roof top tents and load ratings
So you want to stay clear of all the creepy crawlies, snakes, crocodiles, dingoes and/or drunk backpackers and you think a roof top tent is the answer? Please read on for what you need to know.
First of all, it’s not going to be possible to fit a tent on every type of vehicle. You’re going to need to get roof racks but not all styles of roof racks will work. It’s not recommended to put a tent onto a roof rack system that clamps into the top of the door frames. Your vehicle will need to have solid gutters, a track system or raised or solid rails.
Then there is the issue of your vehicle’s maximum load rating which the car’s manufacturer will specify. You will need to add the weight of the tent and the cross bars and any other gear you store up there to make sure you never exceed the max load rating when on the open road. This is known as the ‘dynamic load rating’. If you’re heading off road, a 30% reduction should be applied to the roof rack’s load rating.
When in a stationary position, the total weight of the tent, the occupants and any other gear inside should never be more than double the vehicle manufacturer’s max load rating for the vehicle. This is known as the ‘static load rating’.
Ideally you will spread the weight evenly over the bars with no concentrated weight in any point and especially towards the ends.
You’ll always be better off buying a roof mounted tent where the access ladder is weight bearing and takes some of the load off the roof of the vehicle.
Be aware that you can’t retract these ladders whilst inside the tent so there’s no guarantee you won’t wake up next to a dingo or worse still, a drunk packpacker.
Below is more informtion from Yakima regarding their roof racks including Whispbar and ProRack
Static vs Dynamic Loads
What’s the difference? Put simply, dynamic is when you are driving your vehicle and there is motion, and static
is when your vehicle is stationary.
The load ratings applied to products by roof rack manufacturers are for when you are driving the vehicle, i.e.
they are dynamic load ratings. Static load ratings are generally higher.
Why does this matter? Well, generally it doesn’t, as you don’t add more luggage when you reach your
destination and stop driving.
Where it does come into play though is with roof top tents (RTTs). In the example above, we determined
that you can carry 75 kg on your vehicle. If your RTT weighs 55 kg, you are within your limits by 20 kg
(75 kg – 55 kg = 20 kg).
So, what happens when you climb into your RTT? If you weigh 80 kg, using the dynamic load rating, you would
be now over the limit by 60 kg. Don’t worry though – unless you plan on being in your tent while driving! This
is when the static load rating applies.
As a general rule, in a static environment, the load rating can be increased by a multiple of three (3). So, in this
case, you can load 225 kg onto your roof and you will be ok and actually have 90 kg to spare.
(225 kg – 55 kg – 80 kg = 90 kg)
There are exceptions to this though, which all responsible roof rack manufacturers should make you
aware of. For Yakima and Whispbar, we have a blanket exclusion of all clamp mount systems for use with