“No Bicycle Is Fatigue-Resistant and Safe for Every Potential Use.”

Some modern full-suspension e-mountain bikes have a weight problem. Their maximum permitted total weight is 120 kilograms or just a little more. People with a height of 1.90 metres or more and a preference for the weight bench in the gym quickly reach the limits of what is permitted with such ebikes. Even without a backpack with provisions for a tour and a backup battery. But why is this guideline value so low in some cases? And should you make your purchase decision dependent on it? We asked Tim Salatzki, Head of Technology and Standardisation at the German Cycle Industry Association (ZIV), these and other questions.

Mr Salatzki, why is the maximum permitted total weight of some full-suspension e-mountain bikes relatively low?

The figure is based on a range of different requirements. On the one hand, there is the simple mechanical ability to withstand a load. But it is also about bringing a certain weight to a halt safely and in good time. The braking power plays a major role in determining this limit.

With carbon, many people can probably still understand a lower value. But even with ebikes with aluminium frames, you will find 120 kilograms and only a little more, which can be quite surprising. What influence does the frame material have on these values?

There is no general rule here. After all, no bicycle is designed to withstand fatigue endlessly. The materials, the material composition, the alloys of the metals as well as the joining technology, all of this is designed for a specific use case, a service life and a usage intensity. Like a car. Even a few cars will last a million kilometres. Parts will break at some point. It’s the same with a bicycle.

What other factors does the maximum permitted total weight take into account, apart from the frame material?

Oh, the list is long. For example, my riding style has a very strong influence on the durability of the mechanical components. Do I avoid certain obstacles such as roots or jumps, or do I take everything in my stride? Someone who rides very sportily and uses the bike very intensively puts more strain on the material than someone who rides less.

Of course, that makes sense. What else?

Weight is and remains another important point. If a fairly light person is sitting on the bike, this has a different effect than if a very heavy person is sitting on it. In addition to the frame, this affects parts such as spokes or rims, where a higher weight leads to higher wear. Of course, a bike that is designed for 120 kilograms and is just loaded with 125 kilograms will not break down after five kilometres. However, for safety reasons, the limits should be adhered to as a matter of principle.

You already emphasised the connection between weight and braking power at the beginning. Do we also have to take that into account?

Absolutely. The braking power depends on the weight of the rider and the total weight of the bike. If I overload a bike that is designed for a certain maximum permitted total weight, the risk of a malfunction increases considerably.

So, we have the frame material, riding technique, weight and braking power. Are there any other factors you would consider?

The intended use is also important. In the past, you could buy a bike in a DIY store that looked like a mountain bike but wasn’t one at all. It wasn’t even tested for mountain bike requirements. Before buying, you need to consider what you want to do with the bike. How intensively will you use it and for what purpose?

Well, now this sounds like a rather complex balancing act.

And it is. Especially since this entire matrix cannot be transferred to a fixed number, along the lines of: this bike will last for so long. To make it more transparent, more and more bike manufacturers are listing not only the total weight but also specific usage classes for their models. These show what the ebike is designed for. For example, I learn that this model not only looks more solid, but was designed as a downhill bike and can withstand the corresponding loads.

Can these usage classes be compared from manufacturer to manufacturer, or does each use its own classification?

This is a typical standardisation issue. Ultimately, the classes are derived from a uniform standard. This describes details such as the suitable riding surface and possible jump heights. Again, with smooth transitions. Because a bike that is suitable for jumps of up to 50 centimetres must not break when jumping from a height of 51 centimetres. On the other hand, you have to draw the line somewhere. At the moment, there are definitely manufacturers with their own systems. So, it’s better to read the manufacturer’s definition carefully. Then it will also become clear whether the classes of different manufacturers can really be compared. We at ZIV are doing everything we can to ensure that there are more standardised categories in the future.

Let’s say I want to buy an ebike, but I’m 15 kilograms over the stated maximum weight. Would a dealer be liable to prosecution if he sold me this bike?

Absolutely not. At the same time, you should be made aware that you are exceeding the permitted weight and what the consequences of this could be. With five kilograms, nothing will break. With 15 or 20 kilograms more, it’s a different story. If an accident should ever occur as a result of exceeding this weight, the question of liability will certainly be seriously discussed.

How can we, in very simplified terms, imagine a test procedure for determining the respective limit value?

The basis for this is provided by mechanical test requirements. These have been verified by recording operating loads. The loads acting on the bicycle can now be measured very precisely while it is in motion. We know what forces the bottom bracket, the frame, the stem and so on are exposed to. All of this is known to us and these values are directly linked to real-life riding. Based on the measured values, the corresponding requirements are first defined. Then the necessary tests are carried out on the test stand.

Are these requirements perhaps too high?

Not at all. Excessive testing requirements would actually be counterproductive. Manufacturers would suddenly have to work with greater material thicknesses. The result would be heavier bikes that would certainly be less attractive to customers. However, the bicycle is a living example of lightweight construction. If you compare the weight transported with the weight of the vehicle, the bicycle clearly outshines the car, for example. We have defined the test requirements in such a way that the lightweight bicycle will safely master the intended period of use and the intensity of use. If the weight is not right, I should consider a different model. One whose maximum permitted total weight better takes into account how heavy I am and what loads I usually want to transport with the bicycle. We clearly recommend that you take the respective manufacturer’s guidelines into account.

Is the question of the maximum permitted total weight purely a customer issue or does it play a role for manufacturers as well?

From a legal point of view, it is important for manufacturers to say what the respective bike is designed for. Safety is the top priority here. At the same time, it cannot be fatigue-resistant and safe for every potential use. Otherwise, we would have the standard bike that weighs 50 kilograms and almost never breaks. But nobody wants to ride that.

What development of the guideline value do you expect in the coming years?

We definitely see a trend towards bikes with a higher load capacity. Especially where it comes to taking more than just a laptop to work or children on an ebike. The market demand is there. Manufacturers will always look at what characterises their customers and what their wishes are. If this points towards a higher total weight, a manufacturer will adapt. And the result does not necessarily have to look like a rehabilitation bike, to put it somewhat exaggeratedly.

Thank you very much for the interview, Mr Salatzki.

 

Pictures: German Bicycle Industry Association; Winora-Staiger GmbH; Santa Cruz Bicycles, LLC