Why can’t tires do away with air and use some dense, never flat material? I’ve always wondered, I’m sure there is a good outside physics answer though surely.
Your keyword there is "dense". Rotating weight on a vehicle is basically: bad. But nothing is lighter than air, amirite?
John Dunlop didn't invent the pneumatic tire, but he put it into production. Dunlop's son was getting headaches riding his tricycle, so John D. softened the ride (as pointed out by sibling comment).
And so using air gives us three things that apparently haven't been found with any other material in combination: minimal weight, cushioning, and it can support the weight of the vehicle. If it needs replacing, one need only find an air compressor.
Mostly due to weight, but absorbing impact is another big feature. An air filled tire can absorb a lot of minor road imperfections, a solid tire bike or roller blades can give you an idea of wat a solid tire care would be like.
