Parking Camper On New Driveway Question
Hi All, I just had an asphalt driveway poured at my house, its soft so Im waiting to drive on it for a week or so. I have parked my camper on the old driveway for 12 years on 3x8 blocks but the contra...
Forum Discussion
Reality Check wrote:Reality Check wrote:
but the load on the ground doesn't change unless the footprint does.
HMS.. you make some good points, but I think confusing the subject a bit. 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. Two tires with different psi ratings but having the same profile on the ground (footprint) transfer the exact same load.
i.e. an 8" wide tire with 3" of contact with a 50 psi rating transfers the exact same load as a different, similar sized tire with a 110 psi rating would. The psi on the ground (receiving surface) would not change.
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, and since the load is fixed and the footprint common, ground psi = tire psi.
From a lifetime wasted in engineering and physics.
