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Süddeutsche Zeitung, May 19, 2006
Reading time 3:30 minutes

Handlebar and fork breakage

Bike parts made of carbon are often of minor quality and assembled inappropriately

When Dirk Zedler wants to make his visitors gape, he lifts the jewel of his bike collection with only two fingers. What is impressive about this is not Zedler's strength, but the bike's weight: It weighs less than six kilograms. "You are not allowed to participate in a race with this bike", Zedler smiles. "It is too light." The minimum level of weight in cycling is 6.8 kilograms. "In order to meet this demand, you can attach accessories, additional drinking bottles for example."

The material providing race bikers with such freedom is called carbon. "A fantastic material", rhapsodizes the expert. From the extremely tear-resistant fibres, some resin and hardener parts are made which are stable and much lighter than if made from aluminium, the up-to-now favorite in bike-lightweight-construction. So far, the material has been reserved for experts and higher earners - Zedlers luxury bike costs about 13,000 Euros. But meanwhile also lower priced spare parts for leisure-time-bikers have entered the market whose quality can hardly be judged by the customer and whose assembly is critical. Those, who buy parts of poor quality or makes a mistake during assembly, run the risk of handlebar, seat post or fork braking at full throttle.

The carbon fibre mats were expensive and their processing was the business of experts, says the officially appointed bike-expert. He lifts up a carbon fibre and pulls on it: "It is only inflexible in pull direction and depending on how I align it in the respective part, I get one of good or poor quality." The mechanical engineer warns against low quality parts: "When carbon is offered budget-priced, this means it was not constructed sensibly."

From the outside, you can hardly tell the difference: "The carbon parts' top layer always is a coating, which does not allow for making conclusions on their insides", Zedler says. "It always looks perfect, but inside, it may be a catastrophe." What is left from such parts, often end up in Zedler's office in Ludwigsburg. In a rack, broken bike parts are piling, among them many carbon forks.

Such failures are likely to increase in the future. More and more often, carbon is built in low-priced bikes observed bike expert Rainer Mai from Frankfurt. Besides the insufficient quality of many parts, he criticizes their bad set-up: "The bike industry does not way less attention to the compatibility of parts than the car indstry." Dirk Zedler confirms that meanwhile not only professional race bikes have come to be equipped with carbon, but also middle-priced road-, trekking- or even mountainbikes. But what is justifiable in the high-performance-sector, is not necessarily fit for everyday use, says the engineer: "A big disadvantage of carbon is that I cannot tell after a crash if the bike is damaged."

While professional cyclists usually simply switch to new bikes after a crash, leisure-time-bikers continue riding their bikes after a short visual inspection. "In this case, the risk is high that you go on with a pre-damaged part", Zedler says. To do so, often an apparently harmless incident is enough: "I park my bike and somebody knocks it over - and immediately it can be damaged", Zedler says. Carbon is not fit for everyday use, for off-road usage it isn't anyway.

This apparently applies especially when a bike is upgraded with carbon parts. After all, there is hardly any component which cannot be replaced by a lighter one made from carbon. A discounter advertises this under the keyword "Carbon Tuning". Rainer Mai advises against doing so: "With aluminium, a clamp tightened too much only deforms the part, eg brake lever or seat post. With carbon a sharp edge suffices to cause an invisible tear." Accurate assembly is vital and should be left to experts. They have the neccessary knowledge and tools, eg a torque wrench and assembly paste.

Mistakes in assembly can lead to severe consequences on the road, Zedler confirms: "Handlebars, fork stems or seat posts can break then - even with hith-quality parts." Carbon should be checked for damages quite often, recommends US-manufacturer Trek, where action for damages often is very expensive for enterprises: "Damaged carbon fibres", reads the company's homepage, "can suddenly fail and cause severe injuries or even death."

What was most treacherous about carbon breaks, was that they usually happen without any previous warning", Zedler says. He demonstrates it in his workshop: There, he puts dropped handlebars on one of his test stands. The force, Zedler induces into the part, is not that high: a sideward tensile loading with a weight of 80 kilograms. A racebiker riding out of the saddle could pull at the bar with more force, Zedler says. "An aluminium bar would just slightly bend in this case, you would just exchange it after the race." The expensive carbon part, however, breaks suddenly crisply and without previous warning.

Author: Güven Purtul

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