All about bicycles, electric-assisted bikes, technology and safety in the press

In our daily work as we deal with bicycle safety, technology and user manuals we come across lots of safety risks. The most frequent ones are published in articles of the leading German special-interest magazines TOUR – Europas Rennrad-Magazin Nr. 1, BIKE – Das Mountainbike Magazin Europas Nr. 1 and E-Bike – Das Pedelec-Magazin to make this information important for the sector accessible to a wider public.

For many years now the Eurobike Show Daily accompanying the annual international Eurobike Show has given us the opportunity to publish our perspective on major developments in the cycle industry in full-page articles.

We also speak regularly in independent lectures about all topics relating to bicycle technology and bicycle market. In addition, we are regularly cited by further special-interest magazines or trade journals as well as more and more by radio and television and in their media reports, which shows us that we are completely right with our information. The section NEWS informs you about the latest news from our specialist fields. The reports and publications of this section are listed chronologically or according to topics of interest.

MYBIKE 03/2021
Reading time 1:75 minutes

Measuring the frame stiffness

On our pneumatically operated ECS test stand (“E-Bike Centre-Stiffness”, Zedler-Institute, www.zedler.de) the test bikes are mounted ready to ride, however, without wheels at the drop-outs of frame and fork. Via form-fitting adapters the test stand takes hold of both ends of the crank axle and pulls the bottom bracket area with a defined force to the side, alternately to the right and left from the centre axle. The determined deflection of partly several centimetres is measured and recorded. The values measured in Newton per millimetre (N/mm) document the side stiffness of the respective frame fork system.

Values from 80 N/mmm are currently rated with sub-rating 1 in the category riding safety. Below this value, the rating deteriorates by one grade every 5 Newtons. Handlebars, stem, saddle, seat post and in particular the pannier rack cannot be included in the measurement. Therefore, the final rating of the test bike is always closely connected to the personal feeling during the ride gained through intensive test rides with and without luggage.

Interview

Graduate engineer Dirk Zedler - publicly appointed and sworn in expert for bicycles and electric bicycles

MYBIKE: What are the pitfalls of a low step-through frame compared to a diamond frame?
Similar to a timber-framework the centuries-old principle is a lucky find. Every frame tube omitted reduces the riding stability. In the case of a low step-through frame the front frame area can move more easily compared to the rear area. Designers must give much more thought to stiffness and durability.

Are there differences between classic bicycles and electric-assisted bikes?
Electric-assisted bikes are equipped with heavier components, cyclists take more luggage with them and the drive unit brings more cyclists in hilly terrain at faster rides. Users of electric-assisted bikes also prefer an upright position on the bike. The requirements are therefore significantly higher with electric-assisted bikes. A battery mounted to the pannier rack is therefore extremely questionable. With a battery mounted to the central or down tube, behind or in front of the seat tube, the electric-assisted bike rides clearly better.

How is frame stiffness related to headtube wobbling?
This can be demonstrated with the intube batteries of low step-through frames: Some manufacturers only cut open the tube to integrate the battery. The down tube offers then hardly any torsional resistance. Even if everything else fits, there is a certain uneasiness of the chassis at low speeds already. Handlebar wobbling as a phenomenon, but also the dangerous riding instability when riding downhill, for example when changing the direction, are not only irritating, but also result in accidents.

How can I be sure when buying a bicycle that my desired bike with low step-through entry also offers sufficient riding safety?
The method “looking closely” is not enough. However, MYBIKE tests in which the riding stability is measured and rated during test rides help a lot. In addition, I can only advise to go on a long test ride with an adjusted seating position and definitely with luggage. It is especially the latter that sorts the wheat from the chaff.

Author: Jochen Donner
Photo: Daniel Simon

If you want to read the entire article, order the respective issue from Delius Klasing Verlag online.

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