Normally known for its cars, Chrysler unveiled this monster back in 2003 as a "rolling sculpture" not meant to be ridden but it's believed as many as nine may have been built and sold. With four wheels, it's not a bike in the strictest sense of the word but both front and rear sets move independently, enabling it to countersteer corners just like a traditional motorcycle. Nothing traditional about its engine, though: a 500hp V10 straight out of a Dodge Viper, giving it a theoretical top speed of 480kph. No thanks.
Detonator V4 6.0
Four cylinders, six litres and two wheels would presumably mean more than one set of clean underwear required after a stint on its seat. The Detonator (surely the coolest name ever for a superbike) is now five years old and was created by bike designer Daniel Simon. Looking like it's just crash landed from the distant future, it remains totally unique. With no frame as such, the huge engine sits inside a block under the seat and it's steered using an electromagnetic "sled" behind the front wheel. Astonishing.
In December 2003, Australian designer Tim Cameron sketched a new kind of bike on a scrap of paper and then proceeded to turn it into a computerised 3D model, thinking that was the closest it would ever get to production. He hadn't reckoned on Florida-based engineer and bike builder Christian Travert chancing upon the images while surfing the internet but the result was the V-Rex being made real three years later. Using Harley-Davidson VROD power, you can now buy your very own from a number of US dealers.
Half car, half bike, the Monotracer was the brainchild of a Swissair pilot and stunt aircraft designer called Arnold Wagner. Initially known as the Ecomobile, it has been around for some 20 years. Its enclosed cockpit, with more than a hint of Audi R8 about it, protects the rider and passenger but its most impressive feat is that, with a flick of a handlebar switch, outriggers drop down to keep it steady during impossible-looking cornering moves, with leans of up to 52 degrees.
Victory Vision 800
Shown at the Californian Motorcycle Show in 2005, the Vision has an 800cc flat-twin engine with power put down via a continuously variable transmission (CVT), connected to an exposed driveshaft. There are no foot controls, with all functionality (including the rear brake) located on the handlebars. The front fairing contains storage space for two helmets and gives the bike an extreme front-end bias. Unfortunately, it was never destined for production but it remains one of the finest concepts of all.