My friend with a 2021 RAV4 Hybrid wants to get a roof tent. I was reading the manual, and it says the roof can only hold ~175 lbs. That is basically half the weight of the roof tent, which doesn’t leave much left over for two people on the roof, let alone one.
But I see folks with roof tents on RAV4 and other compact SUVs or cars all the time. Is it safe to put a roof tent, despite the weight rating? Or will the roof eventually buckle with a tent and two people?
I don’t understand how there can be so many roof tents, if the roof rating is so low.
When was it ever safe to overload anything, ever?
Roofs never meant to hold heavy stuff, also putting stuff on top of the roof while driving can fall off and cause accident from air flow force.
I would bet that most of the people you see with roof tents don't even know what an owner's manual is, let alone having read it.
Haha. True.
Follow the manual.
1st of all, the rating is provided with driving in mind. When you load a structural component, it makes it weaker and more prone to buckling. If I stretch out a piece of paper with my hands, and a friend sticks a pencil through the middle, the sheet will tear in half right? That means that if you put of bunch of heavy stuff on the roof, and you get into an accident, the car is going to fold up easier.
That being said, I don't think a rav4 is built for that kind of use. 2 adults and a tent platform? No way.
You will eventually start to signs of stress. It'll spring leaks, crack the paint, stuff like that .
Thanks for the descriptions!
"But I see folks with roof tents on RAV4 and other compact SUVs or cars all the time."
"I don’t understand..."
Well, I see people in California driving 90mph all the time. I don't understand that either. 😕
As Forrest Gump said, "Stupid is as stupid does."
I was thinking either I was right for following the manual, or there might be some nuance I am missing.
@Kaizen I would tend to think that you are right by following the manual. The engineers of the Rav4 included that little tidbit of information for some reason.
It's hard to think of a situation where it's safe to overload anything.
The idea of the rooftop camper is far from new. Some vehicles may have even have had a strong enough roof for it.
that was one of the selling points of the original beetle wasn't it. The arch shape gave the roof immense bridge-like strength.
https://www.youtube.com/watch?v=PGeUSjRMlQ4
Yes! I don't think the Falcon wagon would fare nearly as well though. The old Volvos had impressive roof strength as well.
I was reading the manual, and it says the roof can only hold ~175 lbs.
Definitely those who designed and made this car know the true information so stick with the manual.
Your roof isn't going to support 17,500 pounds.
175 pounds isn't a dynamic load unless it's moving relative to the car. I misspoke, earlier. Brain booting up in the morning. Haha. It's static. If your car goes on a perfectly smooth road going 55, the dynamic load is 0, ignoring drag. As soon as the car changes speed or direction, the weight and the car want to move relative to each other. The car's roof rack needs to put more than 175 pounds on the object to keep them together. That additional force is the dynamic load.
Pictured another way. The fighter pilot flying straight, level and at the same speed. He (the weight on your roof) puts a load on the plane the same as his weight. There's no relative motion or acceleration. He suddenly banks and pulls a 9-g turn. That means the plane is experiencing the same as 9x his weight on the seat. It supports him, or he'll go through it, which defeats the purpose. That's a dynamic load.
The car will not handle correctly with over the listed weight on the roof. The suspension was designed assuming 175 pounds worth of static weight is going to be on the roof, any maneuvering the car has to make with that weight on the roof, the suspension needs to keep the car stable, within reasonable limits. It can tip over if you take corners, etc, too fast. Going outside that parameter increases the likelihood of tipovers. believe me, professional engineers do things like this on a daily basis.
The car will be fine with driving and the tent. It's under 175 lbs. I wouldn't climb on the roof of my car and put 500+ pounds on it. Moving or not.
The sheet metal has minimum strength. The strength is at the pillars,
The roof isn't just there for roll-overs. The "drip rail" (vestigial term) adds longitudinal stiffness which helps keep the cabin space from collapsing, crushing the occupants in frontal collisions.
I can see how that works. It's shaped kinda like a U. I was more describing the metal between those, basically what's over the middle of the car. What you would dent if you put weight on it. Lol. The drip rails are close to the pillars and where luggage racks go.
my point is, when you overload the roof (I'm sure this tent thing clamps onto the sides), you compromise the structural integrity of the occupant area.
I was reading the manual, and it says the roof can only hold ~175 lbs.
This is the maximum load you can put on the roof when the car is moving. It's a dynamic load. Cornering, going over bumps, etc, the roof is designed to at least support that weight in those situations. Plus a safety factor.
Static loads behave quite differently from dynamic. Dynamic loads are higher than static loads; they involve accelerations in directions other than downwards. The force of gravity and the roof's normal force resisting the weight coming through are all that's acting on a static object, negating friction and other unimportant forces. When you turn with a box on the roof, the roof needs to "make" the box on top of go around the corner as well as support the weight. That means it needs to support more than weight. Just sitting there, the roof only needs to support dead weight. Much easier.
Now, your Rav4 isn't an F-15 and able to pull off a 9g turn. The accelerations are less than an additional force of gravity in most instances. The roof safety factor is probably liberal enough to make up for the load changes.
In short:
Think about it. Your car has a thin sheet metal roof that's supported by pillars. The sheet metal has minimum strength. The strength is at the pillars, where the roof rack attaches. The pillars are designed to resist, or at least slow being crushed by the weight of the car in a rollover (these are extremely large dynamic loads). The engineers want to keep you safe if it ends up on the roof. Adding 176 pounds isn't going to make the roof cave in. You're still putting unnecessary stress on something that might save your life one day. I wouldn't do a gimmick rooftop camping experience and risk damaging the roof of my car. Set up a tent on the ground. You'll have less risk of personal injury as well.
Fascinating explanation.
So googling around for static vs dynamic weight, per @justin-shepherd , detailed explanation.
If the dynamic load is 175lbs, the static load can supposedly be 8x-10x this figure. So if this dynamic vs static load thing were correct, then the roof can technically hold the tent and two people.
With that said, I couldn’t find any real hard data or figures to support this claim (nor refute this claim).