Originally Posted by jtownstumpjumper
If one needed to remove tires/wheels to put in metal valve stems......what if you put a ramp on both sides so two tires(1 on each side) could be removed at once....anybody have thoughts on that?
Assuming you ramped the same tires (both front or both back) on each side you would then have a 3 point support with a larger portion of the load shifted off the tires and onto the hitch/landing gear.
In this case each tire would support "about" 1/2 of 2/3 of the weight assuming the CG is equidistant from each support. The wheels will support more the closer the wheels are to the front support and have less "share" the further back.
The math gets complicated as the CG shifts around using varying distances between supports. Also if the wheel locations are such that the CG shifts aft of the supporting axle (possible but not likely) the camper will tip on its "butt" if not restrained.
To simplify the tandem configuration in my previous example, I put the CG of the wheel supported load in the center of the box formed by the 4 wheels.
In the "wheel off" scenario, the CG gets shifted slightly towards the two good tires and just forward (assuming you are changing a rear wheel) of the axle box center due to the support structure changing from a "box" to a "triangle".
Note: I am not disputing the supporting tire/axle will be in shock load; just that it will not be as severe as a 100% overload (the sum of the two tires before lifting) as previously postulated.
The camper itself will "lean" into the flat due to the good wheel on pavement compressing and "squashing" out slightly to support the additional weight.
If the good tire inherited 100% of the flat tire's weight (in the scenario above), the 2000 pound load would become 4000 pounds and would surely blow the tire (typically rated at 2250 pounds on the axle above). In most cases the "good" tire is just fine after you change the blown one (unless it suffered the same impact damage that blew the other) and you will get 100% of the remaining life expectancy.
Personally, I would still just change one at a time using the wheel lift system.
If I wanted both tires on a side off I would use a bottle jack to lift the frame, add axle supports and then release pressure on the bottle jack to support the camper while I worked on the wheels.