valhalla360 wrote:
PSI in the tire is roughly the same as the PSI on the pavement. If you take load off the truck the patch of tire on the ground reduces proportionally so PSI stays roughly the same. (there is some minor variation as the sidewalls of the tire will hold a small bit of load but not a lot. Also the tread pattern plays in a bit but no a lot).
You have difficulty visually seeing the area of the tire patch on the ground but it is changing.
Having done pavement design in a former life, if you are only getting 29psi of strength, you got sold garbage.
Yes, yes and yes..and
I am NOT an engineer, but am required to understand loading, various materials, basic design criteria, etc, for cranes, temporary loads, etc. I think the very low psi rating often used for asphalt is due to creep, as related to it's flow under load. Flow has to do with the stability of the mix, the age and the exposed temperatures. I very well could be using a figure that is to low...but it has worked for us for many years. I couldn't tell you today when or where I settled on accepting that number, which engineer/designer, led us to it. But it works.
Simple example most will understand is a tractor trailer parked in a parking lot...lower the legs, good for a few minutes, hour, no visual effect. Asphalt seems to support it just fine. Come back the next day or week, and you very well might see two perfect depressions.