World's lightest bike

Pop quiz time.  What is the UCI weight limit for bicycles?

a) 17.5 lbs
b) 22 lbs
c) 15 lbs
d) there is no weight limit.

If you answered c, then you are correct. 

There are several bicycles out there that you can purchase from your local bicycle shop that fall below the UCI limit, but there is only one bike that falls so far below it, two of them still will not tip the scales above the 15 lb limit. 

Fairwheel bikes out of Tucson, Arizona has designed the world's lightest race bike.  Tipping the scales at a frighteningly-light 6 lbs!  It's not a stripped down fixie, it has brakes, front and rear derailleurs, a 10-speed cassette,

and AX Lightness carbon fiber rims with titanium spokes. As you can probably guess, the majority of the bike is made out of carbon fiber.

Next to nothing will certainly cost you something.  As Keith Bontrager said: "Strong, light, cheap. Pick two"  This bike - which is not for sale yet - will lighten your wallet by $45,000.