Forum Discussion
Reality_Check
Jun 18, 2017Nomad II
HMS Beagle wrote:Reality Check wrote:Reality Check wrote:
but the load on the ground doesn't change unless the footprint does.
.... PSI in any particular tire only changes the profile of that tire (see above...) but the actual air in a tire does not change the load. ....
The rating of the tire makes no difference. How much pressure is actually in the tire is what makes the difference. Two tires with different psi ratings will have the same footprint if they have the same load and the same actual inflation pressure. I did not mention rating above, only actual pressures. You cannot change the total load by changing the tire pressure - but by changing the tire pressure you change the footprint, which changes the psi seen by the ground. Pressure and load are different things, mathematically related by the area over which the load is spread.
Knowing the load alone tells you nothing about ground pressure. But knowing the tire pressure alone does tell you what the ground pressure is, because the tire will deform until the footprint satisfies the equation: load = footprint x tire psi and since also load = footprint x ground psi, ground psi = tire psi.
From a lifetime wasted in engineering and physics.
Didn't I already say that???
Only problem with this whole side bar, is it has almost nothing to do with the pressure the legs exert when holding up a camper (unless of course the camper is still on the truck, with the legs down...now the load is spread out over...8 points....with the variable of the 'footprint' of the tire coming into play, which in the scheme of light weight campers spread over 8 locations, is almost negligible in world of the RV'er).
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