Building Gravel Bikes
Posted By Gravel Union
On the 20th March 2019
Mirko Meerwaldt took up the craft of frame building last year and recently launched Koppel Frameworks alongside Tom Hoekstra of De Mechanieker. We asked the distinguished designer about the work and thought that goes into making their gravel machines.
Why steel?
We believe in real bikes for real people that are built to be enjoyed and made to last. Our combined years of experience in the cycling and design industries have shaped our views on what we think works best. Many modern innovations in cycling are only changes and not necessarily improvements. So we prefer to work with steel, a material that has proven its lasting value in terms of stiffness/weight/comfort/beauty over time. Steel allows us to offer people custom geometry with clean lines and round tubing, finished by our master painters.
Which decisions do you then have to make in terms of materials?
For this frame, for instance, we chose a stainless T47 bottom bracket shell, alongside an oversized downtube, partly because of the stiffness advantages these offer. That may mean that we are are sacrificing a small amount of ride comfort, compared to a BSA shell and regular tubing, but it looks badass. Also, the threading in the stainless shell is even more reliable than in a regular steel one.
The tubing is all Columbus Zona. It is not the lightest, but that is not what a gravel bike is about. Zona has the perfect characteristics for the purposes of this bike–it’s easy to work with and makes for one hell of a reliable and long-lasting frame. We welded a stainless steel shim into the top of the seat tube. It has been machined to fit the seat post and fight off any oxidation that might occur over the bike’s long life. The triangles are tig welded, and the bridges, dropouts and bottle cage bosses are brazed.
What about geometry?
Tyre clearance is sort of huge. This bike fits 29” Mezcal 2.25 MTB tires with relative ease, although it will probably be ridden with 30-35mm tires. All cables were routed externally to offer easy access and as little obstruction as possible.
All our builds start with a full in-house dynamic bike fit to ensure the perfect compatibility between a bike and the rider’s physique. A full-custom-geometry CAD drawing is made that serves as the basis for the build, which of course differs for road and gravel frames. The geometry for a gravel bike like this is one always a bit ‘lazier’, so it smooths out lumps and bumps in the road and still maintains steady forward momentum. But since custom geometry is everything, the customer has a lot of say in this. If he or she wants a more aggressive position, or different tube set—everything is up for debate. But in the end, we would never make something we do not believe in.
What about the name? What is the story behind ‘Koppel’?
The name Koppel is closely tied to the area in Amersfoort where our workshop is located. The medieval ‘Koppelpoort’ — a gateway into the city — lies nearby, and a number of surrounding streets also have Koppel in their names. We opted to place the logo on top of (and under) the downtube to maintain a clean look, which does not distract from the form of the bike.
And why is there no head badge?
A crest, an abstraction from the St George cross which is Amersfoort’s coat of arms, is painted on the seat tube, so as to not obstruct the head-on view of the frame.