Originally Posted by
makeinu
I doubt the gravel on your road is much bigger than 1" in diameter. If the machine is otherwise optimized, a 6" diameter wheel should easily be able to roll over things smaller than 3" or so...
Big difference: A fixed obstacle as part of solid surface is not the same as a loose surface made up of lots of little bits. The small, short, high pressure (90 psi) contact patch of the A-Bike's 6" tire moves the gravel instead of the bike. The longer, lower pressure (60 psi) contact patch of the Strida's 16" tire rolls over the gravel.
In short: The Strida is ride-able on gravel and the A-Bike isn't.