This is a monowheel inspired by ones made by Kerry Mclean. He's made lots of versions and sizes, but I settled on making this larger version. Here's a pretty good video of one of his smaller ones in action.
It handles in game like you'd expect a single wheeled vehicle to, but by the looks of the videos of actual monowheels, this one is much easier to control. It replaces the freeway, and handles similar to other motorcycles in the game. It's realistic in terms of actually having the 1 wheel that goes around the chassis and drives it. There is only a very small (minuscule) amount of suspension travel, but I set it up so it's still a bit bouncy like what a soft tire would produce.
A problem real monowheels have is called "gerbiling" which is where the chassis spins out of control within the wheel, like when a hampster runs too fast on its wheel. Unfrotunatly I could not achieve this kind of effect in the game - it leans about 90 degrees in both directions before it starts to scrape the ground, even though there are no collision points outside the wheels radius. I thought it might be funny to see the wheel rolling out of control in the game.
All textures are generic GTA textures from various vehicles that i've recycled and tweaked. The seat and engine models are also straight from the Freeway, and the exhaust tips and headlights are borrowed from the Bandito.