Description:

Steering brakes, shock springs, to keep track – with these complex tasks is the telescopic fork (short fork) Mulifunktions a real talent. Reason enough that the good old fork is almost all the alternative front wheel guides in the shade.


The Revolution went past her without a trace. Even in the early motorcycle designed zealous engineers at all possible and impossible alternatives to the fork. From today’s perspective, no matter how sophisticated front suspension many times the task completed as perfect as the front forks. Backlit If this construc-tion more closely, indeed come to light in some obvious weaknesses, but in the sum of their properties, the pipe-in-tube construct is unbeatable. Especially since reversed some theoretical disadvantages in practice. Altered during braking with the front forks, whether upside down or conventional, the steering geometry dramatically depending on travel in the direction of “unstable” and thus in the direction of “handy”.

Small example: by dipping the front while the rear rebound decreases the wake of a Sport Touring bike from 104 to 79 mm, while the steering head angle changed from 65 to 69 degrees, and thus is extremely steep. Because the fork by the tilt (steering head angle) requires not only upward but also to the rear moves, also shortens the wheelbase of 1450 mm to 1405. Overall, the Sport Touring Motorcycle brake theory in this phase that is a highly unstable geometry, but has the advantage that the bike can get on the brakes quickly and easily at an angle. The necessary stability results from the high restoring force of the wake by the braked front wheel.

In the opposite case, ie when full acceleration, cushioned from the front forks and steering geometry is “stable”. Thus, the geometric changes pass through the compression and rebound of the fork almost perfectly to the current driving situation. Forks, pulled or pushed, she made all the forks in their flat resorted Not with the designers dramatically increased support tube diameters (up to 50 mm), before one end of the 1980s placed the entire system on its head. Upside-down, short USD, called himself the thing which brought some important benefits. First, the adverse impact of extreme bending forces site at the lower triple tree with large diameter was defused sustainable. On the other hand pushes the compression and the associated bending moment of the dip tube into the tube, which contributes to many USD structures to stability by the increased overlap.

This high stability is one reason that the diameter of the USD-components in the last 20 years have changed only a few manufacturers. Thus, currently in most large series, only 41 machines, 43 mm or installed in a few cases, 45 mm thick stanchions. What is good for the weight and simultaneously reduces the friction. The handicap of the unwanted high friction between the tube, dip tube and the sealing rings was often the occasion, the front fork to replace it with low-friction wheel designs. BMW was first with Telelever, the newer four-cylinder K with the wheel suspension system a name. There, based on massive wheel, roller-bearing mounted trailing arm from the frame. Suspension and damping is provided by a shock absorber connected between them. so that the fork was in the end? Not at all, because at the new Munich supersport S 1000 RR cushioned no Duolever construction, but a conventional USD forks from Sachs.

Attempts to replace the front forks have been nipped in the approach and, although the alternative BMW front wheel suspension systems are the only world that could establish itself in the market. Reminder: Yamaha tried in 1993 with axle steering on the Sport Tourer GTS 1000 (see photo above), and Bimota wanted to revolutionize the super sports scene with the steering hub in the Tesi 1D. Both systems could not be implemented by the evidence of their theoretical advantages in the field and disappeared from the market. The major disadvantages: expensive and complicated, too low for steering life cycles, indifferent steering transmission.

Because one of the many prototypes have in racing with their alternative wheel guides proved quite clear: For a race were or super sport bike and there is still no better solution than the compact and cost-fork.