At the end of the 70s, Umberto Sala, owner of Birel, launched a new chassis called Drag. Its triangular design and the solution used to manage the braking system made it a very different kart from what had been used up to that time (and even later). Today, it is one of the most sought-after historical karts by enthusiastsread more
Presented in 1968, the Birel Drag is characterized by a triangular type structure: two tubes start from the rear axle and converge towards the front until they join. Here, at furthest point of the frame, there is the steering shaft attachment, formed by two tubes supporting the uniball. An additional tube, always smaller in diameter, positioned above the uniball serves to fasten the oval-shaped number-bearing plate, which was mandatory at that time to display the race number.
The main frame sizes are: 1010 mm wheelbase, 800 mm rear track width and 740 mm front track width. The diameter of the two main longerons is 30 mm. On each one of them two shorter tubes are fastened which go to the chassis’ Cs, one is always 30 mm in diameter, while the other has a smaller diameter, used to increase the rigidity. This very particular design created a sort of mechanical suspension at the front and it distinguishes the Birel Drag from all the chassis of the time as well as those used today. At the rear, the 25 mm axle is not fastened by means of an axle support bearing as in modern karts but passes directly inside the chassis and rotates on its bearings. Always at the rear, one notices the absence of the bumper, as the chassis ends with a straight bar. The muffler, the most protruding element, is protected by a secondary tube, welded precisely with the objective of preventing the exhaust from leaking in the event of a rear-end collision.
In the Birel Drag analyzed in this article, the brake system is present only in the rear of the kart. The kart, in fact, is a 100-cc direct-drive configuration. In the 125-cc shifter-karts the brakes were in the front as well, as it is done in the current models. The brake is mechanical: the steel cable starts from the pedal and joins directly to the brake caliper which, therefore, is initiated by the direct action of the driver. The caliper is formed by two half-shells and is fastened by means of a chassis support in a vertical position. The brake disc is neither ventilated or in a floating configuration. As it is not hydraulic, the brake system does not have a self-adjusting caliper. Any pad wear could be compensated by inserting shims between the pad and its seat on the caliper itself.