If you’re gearing up for a big trip—maybe heading up to the High Country or just a weekend run down to the coast—you’ve probably taken a look at the little sticker on your roof racks or the manual in your glovebox and seen a number like “75kg” or “100kg.”
Then you look at your Roof Top Tent (RTT), which weighs 65kg, and you think about yourself and your partner climbing in there. Suddenly, you’re doing the maths and wondering if you’re about to turn your SUV into a convertible.
It’s easily the most common question we get here at our Dandenong South showroom. People are worried they’re going to crush their roof, or worse, have their gear fly off on the Monash. To get it right, you need to understand the difference between dynamic and static loads. It sounds technical, but it’s actually pretty straightforward once you break it down.
How Much Gear Can I Carry on My Roof Racks?
When calculating how much weight you can carry on top of your vehicle, there are a few key factors to consider:
- Load ratings for each component that makes up your carrying system
- Static vs dynamic forces
- On-road vs off-road usage
1. Dynamic Load (The “Driving” Weight)
Think of the dynamic load rating as the weight your car can handle while you’re actually moving.
When you’re doing 100km/h and you hit a pothole or have to swerve suddenly to miss a roo, that gear on your roof isn’t just sitting there—it’s exerting massive amounts of force on your roof’s mounting points. A 60kg tent can feel like double that weight the second you hit a bump.
Safety first: If you go over this limit, your car becomes “top-heavy.” You will feel the car swaying more in corners, and in a worst-case scenario, it can actually cause a rollover.
The insurance side: This is the big one. If you’re involved in an accident and your roof was overloaded, your insurance company will look for any reason to knock back your claim. Following the dynamic limit keeps you legal and covered.
2. Static Load (The “Campsite” Weight)
The static load rating is what your roof can hold when the car is parked and you’ve set up camp.
This is where people breathe a sigh of relief. Your car’s frame (the pillars that hold up the roof) is incredibly strong when the car is standing still. As a general rule, in a static environment the load rating increases by a multiple of three. So if your dynamic load rating is 100kg, then your static load rating is 300kg.This is how you can have a 70kg tent, plus two adults and maybe a dog inside, without the roof buckling.
The tent just needs to be under the limit while you’re driving; once you’re parked, the car can easily handle the extra weight of the people inside.
Important note: While the 3x multiplier is a good rule of thumb for roof rack components and most vehicle roofs, always refer back to your vehicle manufacturer to confirm if it applies to your specific vehicle.
3. The “Off-Road” Factor (Do Not Skip This Part!)
We love our corrugated tracks in Australia, but they are absolutely brutal on roof racks.
All load ratings are applicable for driving on well-formed sealed roads with a smooth surface. Once you start travelling on any unpaved or poorly maintained roads, the maximum amount of weight you can carry may reduce depending on your roof carrying solution.
Most of the big brands we carry, like Yakima, Atera, and Prorack, have specific off-road reduction guidelines. Because the vibrations on a dirt track are so constant and violent, they typically recommend a reduction in your load rating based on your fit type:
- Clamp mount kits (naked roof): 50% reduction
- Most other fit types (track, fixed point, raised rail, flush rail, gutter mount): 33% reduction
So, if your racks are rated for 100kg on the bitumen with a track mount, you should really only be carrying about 67kg if you’re planning to tackle the Oodnadatta Track or the Gibb River Road.
If you’re planning on doing some serious 4WDing, that’s when you should look at something like the Yakima LockNLoad Platform—it’s built specifically to handle that kind of punishment, with the RuggedLine mounting system offering robust off-road performance.
Note: Extreme four-wheel driving such as rock crawling is typically not covered by manufacturer warranties, regardless of fit type.
4. How to Work Out Your Actual Capacity
Don’t just take the number on the box and run with it. The component in your carrying system with the lowest load rating dictates the maximum load rating of the entire system. You need to check:
Step 1: Check your vehicle’s manual
Find the “Maximum Roof Load.” This is the gold standard. Even if your racks say they can hold 100kg, if your car manual says 75kg, the car wins.
Step 2: Check your crossbar/platform load rating
Different products have different ratings. Here are some examples from popular Yakima and Atera products:
- Yakima JetStream / JetStream FX: 75kg
- Yakima Aero ThruBar / RailBar / FlushBar: 75kg
- Atera Signo RTD bars: 100kg
- Altera Signo RT bars: 100kg
- Yakima TrimHD (2 bars) Platforms: 100kg
- Yakima TrimHD (3 bars) Platforms: 150kg
Step 3: Check your leg/mounting system load rating
- Yakima BaseLine / BaseLine FX / TimberLine FX: 75kg
- Yakima TimberLine / SkyLine / SightLine / HD Leg Kit / TrackTower: 100kg
- Yakima LockNLoad RuggedLine: 100kg–150kg (depending on SKU)
- Yakima OverHaul / OutPost / BedRock with HD Bars: up to 227kg
Step 4: Subtract the weight of your carrying system
Your crossbars and legs usually weigh around 5kg to 7kg combined. A platform system can weigh 25kg to 40kg.
Step 5: What’s left is for your gear
If your limit is 75kg and your carrying system weighs 7kg, you’ve got 68kg left for your tent, bikes, or kayak.
Worked Example: Car Roof Rack and Roof Box
Let’s say you have:
Component Load Rating
Vehicle roof load rating 65kg
Roof rack (crossbars and legs) load rating 75kg
Fitting kit load rating 100kg
Roof box load rating 75kg
Your maximum load rating is 65kg because that’s the lowest component rating.
If your carrying system (legs, crossbars, and roof box) weighs 25.6kg total, your maximum on-road load capacity is 39.4kg for additional cargo inside the box.
5. Proper Load Balancing
Now that you know your numbers, here’s how to load safely. When loading up your roof racks, remember these recommended practices:
- Ensure all cargo is evenly distributed across the rack or platform to maintain vehicle stability
- Use approved securing methods, such as high-quality tie-down straps and hood anchors
- For kayaks, surfboards, and SUPs, always secure with bow and stern tie-downs to vehicle recovery points or using a hood anchor
- Keep camera sensors on the windscreen unobstructed
- In high-wind scenarios or when carrying long or overhanging items, reduce vehicle speed accordingly
- When driving in off-road or rough terrain environments, lower speeds to match the terrain and minimise stress on the mounting system
6. Roof Top Tent Restrictions
If you’re planning to mount a roof top tent, there are some important restrictions to be aware of.
Yakima does not advise the fitment of roof top tents onto clamp mounts unless otherwise specified as approved. If you’re unsure whether your setup is suitable for an RTT, come and have a chat with us—we’ll make sure you get the right system for your needs.
Why Getting a Pro to Fit Them Matters
At the end of the day, you are putting a lot of trust in a few bolts and some metal brackets. Especially with modern cars having panoramic glass roofs or unusual “flush” rails, it is easy to get it wrong.
At Roof Rack and Box, we’ve seen it all. We don’t just sell you a set of bars; we make sure they’re the right ones for your specific car and what you’re planning to do with it. Whether you’re setting up a brand-new Ford Ranger for a lap of the country or just putting a cargo pod on the family SUV, we’ll make sure it’s safe, legal, and solid as a rock.
If you’re confused by the numbers, don’t risk it. Give us a buzz or drop into the shop in Dandenong South. We’d rather spend ten minutes explaining the maths to you than you lose your gear halfway to Mt Buller!