For professional cyclists, weight tuning stops at a weight of 6.8 kilograms: According to the regulations of the World Cycling Union, racing bikes in the professional category are not allowed to be lighter. With the "Project 3.9", the German mail order company "Canyon" (Radsport Arnold, active in Switzerland as "Coast") and lightweight construction guru Christian Smolik show what is minimally possible, based on the standard "Carbon Ultimate" racing bike frame. Due to the unusual Smolik rear derailleur, there are only 5 gears to choose from at the rear, but a real front derailleur controls two carbon chainrings mounted on a titanium crank. The project name immediately gives away the weight: the bike weighs an incredible 3.9 kilograms ? or a good three kilos too little in the eyes of the World Cycling Federation.