I didn't mark disagree even though I don't agree with your math.
It is a discussion. No one is right all the time. Anyone took the time to post, explains and help out others with good intention should be appreciated.
The PSI inside the tire is NOT the same as the PSI on the tile. However, the force exerted by the entire wheel to the tile and the force received by the tiles is obviously the same.
P=F/A ... let's look at A. The area of the tire internal surface area should be used to calculated the tire PSI, not the area of the contact point. The contact point of the tire to the tile should be used to calculated the tile PSI. So A is different.
For the force F, the force of the tire PSI is the force of air inside exerted on the internal tire wall. Not the weight of the car. It is the volume of the air. (U can skip to the 2nd last line of this paragraph if you agree.
) It is like squeezing a ballon will not affect it's PSI as long as the ballon can expand (PV=K). F is the force created by the difference between air pressure inside and the outside atmospheric pressure. F or the PSI of the tire will increase with higher attitude due to lower atmospheric pressure, but ironically, not related to the weight of the car. The weight of the car will increase the F indirectly only if it decreases the volume of the tire (not the shape). That explains why the tire is 45 PSI when it is on or off the car (P1 or P2). With heavy load, it is true that the contact point will increase and makes the wheel looks smaller, but the tire side wall as well as the entire shape of the wheel will also expand to maintain the internal air volume constant up to certain limit. (P1V1=P2V2, if P1=P2, V1=V2) With extreme heavy weight when the tire cannot expand anymore to compensate for the volume, the PSI will increase. In other words, the elasticity of the tire material (summer tire vs winter tire vs sports tire) in combination of the weight of the car will affect the tire PSI. Not the car weight alone. Meanwhile, the F on the tiles is simply total weight of the car divided by 4 not affected by attitude or temperature. So, F is different.
If the F and A of the tire and tile PSI formula are different, their PSI cannot be the same. Going back to the original question: "Is the X too heavy for a tile floor garage?" ... I don't know