Interview with a frame builder: What makes steel bicycle frames so special?

Steel bicycle frames are considered durable, heavy, comfortable and exotic. Today, filigree steel tubes are only found on a few bicycles. And when a bike with a steel frame does appear, it is often either a retro classic or a very special one-off. Compared to aluminium or carbon, steel only plays a minor but very special role. We asked Leo from Leovelo ten questions about steel. In his frame building courses, Leo shows interested parties how they can solder their own customised chassis from classic steel. In the interview, he tells us why steel frames usually have an emotional value and whether you really need to be afraid of rust.

How a steel frame is created

BIKE: How do you build a steel frame?

LEOVELO: In my frame building course, we start with a bike fitting. The values from the bike fitting machine and a discussion about the rider's preferences can then be transferred to a geometry sketch. The next step is to select the materials, i.e. the different tubes. The construction itself always follows the same pattern for a normal frame. We start by preparing the bottom bracket and the head tube. We then adjust the other tubes to the correct length. All parts must be ground to the millimetre. Once they fit together perfectly in the frame building jig, they are joined together by soldering.

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What are the differences in the base material of a steel frame?

There are fundamental differences in the alloy. For example, 25CrMo4, the most commonly used steel in bicycle construction, is common. Other tube sets, such as Columbus "Live" and Spirit", have different alloys and achieve a higher tensile strength. There are also special stainless steel variants. Another difference is the material thickness. Thin-walled steel frames can be comparatively light, but the rigidity and stability must of course also be suitable.

Where do the tubes for a steel frame come from?

I almost exclusively use tubes from Columbus in Milan. Frame builders can buy certain quantities from them. But there are also other manufacturers of steel tubes, such as Reynolds from the UK.

Steel bicycle frames: something very special

What makes steel frames so special?

Steel is the material with the greatest history in frame construction and therefore always has a kind of classic effect. This makes steel particularly attractive to enthusiasts. Aluminium frames have become larger and larger over time. Steel, on the other hand, allows for slimmer silhouettes due to its different density and stability. It is easy to work with and, unlike titanium, for example, does not require any clinical prerequisites and, unlike aluminium, no elaborate fixtures in frame construction. Over the decades, many frame builders have learnt to work well with steel. From a purely technical point of view, however, it is no longer the most sensible choice of material for a bicycle frame.

What are the advantages of a steel frame when riding?

This question is difficult to answer rationally. A steel frame can be particularly aesthetic and beautiful. Above all, a self-built steel frame, in which all parameters have been individually determined, creates an emotional connection to the bike. Once you have gone through all the work steps yourself, you end up loving your bike more than anything.

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Why are there so few steel bicycle frames left today?

This certainly has to do with the further development of materials such as aluminium or carbon. Over time, steel has become less important for frame construction and is now more a material for enthusiasts than for competition. In the sporting sector, it's always about "higher, further, faster". There are now simply better rational solutions than a steel frame.

How do steel frames from your course differ from those from series production?

In individual production, there is always a big process around a frame. Each time, new parameters come together that need to be customised. In mass production, it's a completely different story. For example, there is a specially set up gauge for each work step in order to be able to build large quantities as efficiently as possible. I also always try to keep the weight of Leovelo frames as low as possible and avoid "hidden" weights due to thick-walled bottom brackets or head tubes. For a clean look, I rely on internal cable routing. There is an infinite amount of attention to detail in every frame.

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Steel: durable and sustainable

How can I recognise a good steel frame?

Most standard steel frames usually have durable seams and a consistent build quality. If the manufacturer is not recognisable, for example on the second-hand market, there may be a tube set sticker somewhere. I like to knock on the tubes and listen carefully to the resonance. This allows me to draw conclusions about the wall thickness and material. The weight is also an indicator of the quality of a steel frame.

How do you rate the sustainability of steel?

I am not an aluminium expert, but I do know that the bauxite required as a raw material must be a major environmental sin. The recyclability of carbon is also limited. Steel, on the other hand, is known for its good recyclability. Steel is relatively easy to repair and is popularly regarded as particularly durable. However, I once had the opportunity to work in a testing institute for bicycle parts and have moved away from this philosophy somewhat. The material of a classic steel frame with thick walls of 0.8 to one millimetre vibrates extremely little and is very stable. Modern steel frames are usually lighter but also more sensitive. A fall on an edge is always met with dents or other damage. However, I must also say that talking about the sustainability of a steel frame that is completely covered in aluminium and carbon parts only makes sense to a certain extent.

Do steel frames need special care?

This also depends on where you live. Rainwater is less harmful to steel frames than salt water. If you live near the sea, for example, you should take particular care to ensure that the cavities are well preserved. If a frame has been carefully washed and professionally preserved after brazing, steel frame riders need not worry about maintenance. The steel is protected under the coating, for example with paint. However, if the coating is damaged, road salt can be a problem.

Conclusion

I'm a big fan of steel frames myself and appreciate the classic material above all for its lively riding characteristics. I like the natural flex in the material, especially on hardtails and gravel bikes. In addition, a well-made steel frame stands out from the crowd and I like the filigree look. A customised steel frame is, of course, the ultimate. - Jan Timmermann, Bike Editor