So I called Frontrunner where I got my RTT. Turns out there is not a simple answer to this. A lot depends on the type of factory rack you have. If you have the side rail type and not the race type you are in better shape. I was told 150 -200 pounds as long as the cross bars use a wrap around system to attached to the side rails. That also depends on how hard you off road, and knowing that you need to check the bolting system and clamping system prior to going and after going off road. At this weight you still need to check it constantly to be sure it is tight. I have 83 pounds with my Frontrunner RTT and check weekly using factory side rails and Yakima cross bars. When the tent is pitched and stationary you can add an additional 200 plus pounds, but it sound like you are getting right to the max with the medium sized tent up there. I would look into a fully supported rack system or a different type of RTT.