Blimey Mike - it's Newton's third law( Gospel since 1687) & you think it doesn't make sense!!!!!!!quote]
I'm not disputing Newton, I'm disputing whether orezok's response added any value to the question. Going to a ridiculous extreme even 1/4" luan plywood will hold up a tractor if the plywood is adequately supported. We're not discussing the compressive strength of a material but the tensile strength of a composite system.
If a 1" square post 4" tall were fastened to the floor & the tractor driven up onto it, provided it didn't puncture the tire, do you really believe it would only exert 30 lbs on the floor ???? Or that the tire pressure would suddenly spike to 2500 psi ????
If a single wheel tractor is 2500lbs & is capable of balancing on 1" sq post, then the floor loading is 2500psi AND THEREFORE SO IS THE TYRE PRESSURE. What else could it be? It may not be precisely 2500psi due to tyre tread/wall stiffness etc, but the 2500lbs have to be supported on something?
The result will be a blown tyre or a puncture, I suspect. If the tyre could stand it, it might deform as the pressure increases until the post pushes the tread against the rim well, in which case the pressure would be less since the rim well would now take some of the loading.
Its more difficult with a multiwheel situation, since the single wheel weight transfers to the other wheels , but if you could simultaneously raise all 4 wheels with 1" sq posts then each tyre would have to support 2500/4 = 625psi,(assuming equal weight distribution) which would still give you 4 simultaneous punctures!