I found a junkyard jack from a pickup truck to mount the spare tire on my motorhome. The unmounted tire is 53 pounds, rim another 30 - 40 pounds. It is not light, and needs something substantial to hold it while it is bouncing down the roadway.
Many I have seen mounted under the A-frame part of the trailer, rather than the back that seems to drag while going out of a driveway, such as a gas station. Not under the actual a-frame, but rearward under and between the frame rails, where it is tucked up nice and safe from being crushed by the RV going out of a driveway.
Good luck,
Fred.
