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davidmoffitt t1_jbkwvlu wrote

Reply to comment by nalc in Reinforcing wooden garage floor for vehicle by nalc

WTAF would tire pressure have to do with anything? Weight is weight, gravity is gravity, do you think a 100lb bag of feathers differs from 100lb drum of water? 🤣

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nalc OP t1_jblpxmo wrote

>WTAF would tire pressure have to do with anything?

The contact patch of a tire is the weight of the vehicle divided four divided by the tire pressure. So if you're calculating a maximum loading it's kind of important. I don't have any doubts of the floor's ability to support the weight of the car if it was evenly distributed over 280 sq ft. But it's not, it's distributed over four 0.2 sq ft contact patches each totaling about 1,000 lbs. So obviously the worst case scenario is the weight of the tire right in the middle ~2" of a 14.5" unsupported span of 5/8" plywood causing the plywood to crack. The compressive strength of wood is on the order of 1 ksi so I'm not worried about the 4x4 skids or even about the joist compression (since each 2x4 joist has about 5 sq in of contact to the skid). I have struggled to find good resources on plywood strength over short distances with very concentrated loads so that's why I'm asking for advice.

Would you rather someone drop 100 lbs bag of feathers or 100 lb of water on your head? I know which I'd prefer.

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bigloser42 t1_jbm2z5m wrote

For the purposes of what you are doing, the tire pressure & contact patch size is almost irrelevant. You’re talking about a difference of a few square inches at best. Weight is far more important.

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