How Big of a Hover Monster Truck Would I Need to Have?

i want to build a hover monster truck with helium tires. i can't stop thinking about how good babies smell. Babies are just absolutely, the thing that gap me most about babies is that, despite having essentially none of the things i associate with humanness, they're little people. I'm getting a little baby crazy. Ah, i can't believe this podcast wasn't brought to anyone by baby smell. Hank, we need to answer another question. How big do the tires have to be? Can we just say off the ground, because atmospheric pressure changes a lot as you get up into the stratosphere and that would make the tires different.