Roof top tents and load ratings

Roof top tents and load ratings

Roof top tents are becoming more and more popular, for those people that want to discover Australia. You can sleep on your roof, staying away from those creepy crawlies.

Thinking 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 supporting racks. Your vehicle will need to have solid gutters, a track system or raised or solid rails. Generally, you need to have minimum 2 cross bars but can also be connected to platforms. Not all styles of roof racks will work. Be aware that most roof top tents have connecting u bolts and support longitudinal supports, so take note of the connectors before buying your roof rack.

It’s not recommended to put a tent onto a roof rack system that clamps into the top of the door frames.

Next up is the issue of your vehicle’s maximum load rating which the car’s manufacturer will specify. You will need to add the self-weight of the tent plus the self-weight of the roof racks (and any other gear you store on or inside the tent, to make sure you never exceed the max load rating while travelling. This is known as the ‘dynamic load rating’. If you’re heading onto dirt roads, a 33% reduction should be applied to the vehicles 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 the “general rule” of three times the vehicle manufacturer’s maximum load rating for the vehicle. See example below.

Dynamic vs Static Loads

Static is when your vehicle is stationary. You have a spare 75kg x 3=225kgs-45kg-5kgs – weight of 2 x bodies, say 80kgs each=160kgs = 15kgs, so your racks are sufficient carrying limits.

There are exceptions to this, which all responsible roof rack manufacturers should make you aware of, so keep up to date on the rack manufactures websites. This should never exceed to load rating as outlined by the vehicle manufacturer.

Rack manufacturers have a blanket exclusion of all rubber mounted clamp mount systems for use. 

Dynamic is when you are driving your vehicle and there is motion. The load roof ratings applied the car manufacturing are for when you are driving the vehicle on sealed roads, i.e. they are dynamic load ratings. If you’re heading onto dirt roads, a 33% reduction is applied to the vehicles load ratings.

Carrying Capacity-1
(Rhino-Rack February 2021)

OR – On Road, or bitumen, sealed roads allowance

OFR – Off ROAD, DIrt, Unsealed, Sand etc allowance

VLL – Vehicle Roof Limit Load (must check vehicle owners manual/handbook/log book for specific figure)

Examples

Lets assume a Vehicle Roof Load limit (VLL) is 75kgs, (according and subject to manufactures load limits, see log book)

System weight (SW), self weight of racks = 5kgs,

Luggage weight = 45kgs

Example 1: Bitumen Roads with roof bars weighing 5kg

On road cargo allowance (OR) = VLL-SW

On Road = 75kg-5kg

On Road = 70kg maximum

If carrying luggage = 45kg (e.g. a roof top tent)

70kg-45kg = 25kg remaining for other items.

Example 2: Dirt Roads with roof bars weighing 5kg

Off road cargo allowance (OFR) = (OR)/1.5

Using the same figures from example 1.

Off Road = 70kg/1.5

Off Road = 46.67kg

If carrying luggage = 45kg (e.g. a roof top tent)

46.67kg-45kg = 1.67kg remaining for other items.

Example 3: Bitumen Roads with platform or basket weighing 25kg

On road cargo allowance (OR) = VLL-SW

On Road = 75kg-25kg

On Road = 50kg maximum

If carrying luggage = 45kg (e.g. a roof top tent)

50kg-45kg = 5kg remaining for other items.

Example 4: Dirt Roads with platform or basket weighing 25kg

Off road cargo allowance (OFR) = (OR)/1.5

Using the same figures from example 1.

Off Road = 50kg/1.5

Off Road = 33.33kg

It is not safe to carry a roof top tent as the 45kg item exceeds the 33.33kg limit. Consider a different distributioin of your luggage.

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