Understanding roof weight limits

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lucferros

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So I’m considering putting a roof rack with a roof top tent on top of a 2018 Ram 1500 crew cab and while the racks all have various load limits for dynamic and static loads, I can’t seem to a straight answer as to how much load the roof itself can take when static. Generally I’m finding answers around the range of 150-165lbs, but I’m not clear if that refers to evenly distributed load or if the edge points where roof racks are installed are somehow able to take greater loads that most people might expect. And if that’s the case does that mean everyone is regularly overloading the roofs of their vehicles when they sleep up there?

I know so many people do this kind of thing, but I’m going to be putting 2 adults 2 kids under 10 and 2 medium size dogs up there and just want to make sure I’m understanding these limits correctly. Thanks to all.
 

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I would be assuming that is the dynamic load as is similar to most modern 4X4s. Land Rovers and Toyotas are approx 75kg

A decent rack will distribute the load for you.

If you look in owner manual it is sometimes under towing / load

To be safe double the dynamic to get static and you will be within parameters._
 

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If the roof rack will be covered completly by the tent you should go for some simple roof bars. Less weight on top.
 

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So understanding how much weight it will take needs understanding how it's built. Without some serious reinforcement I don't think it will fly even distributing the weight out to the sides. That's a lot of weight when you crawl up there for a good night's sleep.
Just my .38 cents.
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ThundahBeagle

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So I’m considering putting a roof rack with a roof top tent on top of a 2018 Ram 1500 crew cab and while the racks all have various load limits for dynamic and static loads, I can’t seem to a straight answer as to how much load the roof itself can take when static. Generally I’m finding answers around the range of 150-165lbs, but I’m not clear if that refers to evenly distributed load or if the edge points where roof racks are installed are somehow able to take greater loads that most people might expect. And if that’s the case does that mean everyone is regularly overloading the roofs of their vehicles when they sleep up there?

I know so many people do this kind of thing, but I’m going to be putting 2 adults 2 kids under 10 and 2 medium size dogs up there and just want to make sure I’m understanding these limits correctly. Thanks to all.
With a Ram 1500, I think most people get a special bed rack and put the RTT on top of that. Its rated for that kind of weight and connects to the bed, which is rated for more weight than the roof is
 
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genocache

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So I think that finding info will depend on testing and it is not likely that the mfr will load the roof to collapse. The dynamic load however affects suspension and handling because that raises the center of gravity and that affects performance both on and off road. Something the mfr is likely to measure.
And let's face it you have a crapload of weight up there and go running at 65mph down some washboarded road something will probably give, or you are on the offcamber section of Steele Pass with all that weight, you will be white knuckling it and the wifey will be out walking. However that night and the RTT up, probably sleep well, it might rock in the wind or as one turns over.
 
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I think the bed rack mounted solution is the answer. If you say 200 lbs for you, 125 lbs for the wife, 150 total for the kids, and maybe 75 total for the dogs, you are at 550 Lbs! Plus the weight of the rack, and the RTT you could easily be at 750 to 800 lbs! If you then divide that by the number of contact points to the roof, it's still a lot in my eyes.

Good on you for thinking and asking the questions!! Having that weight lower and hiding behind the cab seems better to me. Was there some specific reason you wanted it up on the roof?
 
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leeloo

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Static load is not an issue on most cars.
Roofs are part of the crash protection system and a roof can take a lot. In a roll over the cabin needs to stay intact, so they are build pretty solid, they should support the weight of the car at minimum. In a dynamic load you have shear forces so it is more complicated, hence the limitations and the dynamic rating.
I had a very heavy hardshell RTT and 3 of us were sleeping in it, I would say the tent 75 kg + cross bars another 5 + 210 kg my wife, me and kid ( me 100 :) out of 210 total ) so a total of 290 kg or ~ 650 lbs, and I had no issues with the roof. It was a Landcruiser j120 and the roof was rated for 100 kg dynamic load.