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Eurobike Show Daily 2017 - Day 2
Here is the background on ISO 4210, along with my recommendations on other steps that bike manufacturers should take beyond the standard for the good of their customers and the health of their business.
ISO 4210 outlines a process for testing the fatigue strength of components. Its testing requirements are built on three pillars: fatigue (caused by recurring loads); overloading; and impacts (which are less frequent events.) With relatively simple test setups, manufacturers can carry out ISO-compliant tests and ensure a certain degree of operational safety. If every bike and component were tested in accordance with ISO 4210, there would be far fewer component failures and subsequent accidents.
Good, but not good enough. However, the standard is inconsistent because it does not apply all three “pillars” to its requirements for testing bike components. Pedals, for example, are required to undergo impact tests, but cranks are not. Yet there is no denying that a high load on a pedal, caused by a failed jump or a fall, is also transmitted to the crank and bottom bracket.
The standard also requires that some components be tested to different loads, even if, like a pedal and a crank, they are directly connected to one another. Frames and forks are one example. Using the standardized falling weight, a carbon fork needs to be tested at a falling height of 640mm, while a road frame must be tested at a falling height of only 212mm.
The ISO standard also contains gaps. Forks must undergo a disc brake load test, but not frames. One of the most egregious omissions concerns the steerer tube of a carbon fork. Although it is one of the most critical components of a road bike, there is no requirement in ISO 4210 that it be tested. Yet failures of carbon steerer tubes have forced many renowned bike brands to issue product recalls.
Higher standards. While it is crucial to test bikes in accordance with ISO 4210, it is not enough — and does not by itself ensure a safe bicycle. For this reason, some testing labs, including the Zedler Institute, and manufacturers have developed their own testing requirements that go beyond ISO 4210.
Recognized test labs use different criteria to differentiate between a bike’s intended use and permissible total weight, and distinguish between electric and conventional bikes. Manufacturers that seek to minimize product failures should establish their own, reasonable testing standards. Or, if they choose to partner with a testing lab, they should first ask these questions:
• Does the lab perform individual tests with one test piece — the preferred option — or does it use a new test piece for each load case — a poor practice that, absurdly, is allowed under ISO 4210?
• Does the lab complement the ISO required tests with tests on such essential components that aren’t mentioned in the standard, such as disc brakes, fork steerer tubes, the rear triangle on full-suspension frames, and, for impact tests, the rear triangle of all mountain bike frames?
• Does the lab vary test loads to account for different types of use? For example, mountain bikes should be tested at different loads depending whether they are intended for cross-country, allmountain, enduro, freeride or downhill use.
• Does the lab use more realistic load types and levels beyond those stipulated by the standard?
• Does the lab perform materialspecific tests? Mechanical accuracy is another important and often neglected aspect of a test procedure. Test pieces must be mounted as realistically as possible — something not always specified by the standard. For example, dropouts should be tested only when they are clamped on the actual thru axles or quick-releases they are paired with, so that the loads acting on them better reflect real-world riding conditions.
Read the entire article here.
Author: Dirk Zedler
Ossweiler Blaettle, 2019/03/28