Stiffness of steering head - steering stability
The frame's stability at the steering head is decisive for the feeling you have when riding the bike and the safety reserve the road bike has in difficult situations. The TOUR-way of measuring the stiffness of the steering head indicates the steering stability of a bike under the influence of different road surfaces, gusts of wind or a rider shaking with cold. High measured values indicate high safety against unintended frame oscillation and provide precision - especially at high speed. In January, the established test station was replaced by a new mobile one. The test proceedure remains the same, the results can be compared. The frame is horizontally fixed at the rear drop outs with quick release levers and propped up at the middle of the head tube. Instead of the fork, a steel tube is put into the head tube and fixed by two cones. While the test weight, which is placed one metre away, warps the frame, the measuring device, which is placed 400 millimetres away, indicates the deflection. From the deflection and the torsional moment induced, TOUR calculates the stiffness of the steering head in newtonmetres per degree (Nm/°). The steering stability is 15 % of the final result.
Unnecessary hardness combined with consistent road vibrations leads to the rider getting tired early. Therefore, comfort is also important when it comes to road bikes. Special frame types and the possibility of giving carbon parts special characteristics by aligning the fibres in a certain direction, make diamond frames for the first time more comfortable than their classic predecessors made of steel or aluminium. With its newly developed comfort test station, TOUR can now check the frame comfort. The frame set is vertically mounted to the station at the rear drop outs. Frame and fork can deflect and dodge realistically on the front roller. A fitting seat post is assembled and fixed at a seat height of 750 millimetres between the middle of the bottom bracket and the middle of the saddle frame. A defined force (102,7 kg) is applied vertically 70 millimetres behind the intersection of seat tube and saddle frame. At the same time, the deflection is measured from the same distance. By dividing the force by the way, you get the deflection hardness of the frame, which is 7.5 % of the final result.
Author: Matthias Borchers