4 Interesting Prototypes From Emerging European Brands

While the big players of the bike industry tend to keep the details of new frame designs under wraps (quite literally), the smaller, more boutique manufacturers are often more forthcoming about what they're developing. Though budgets are infinitesimally small in contrast to the huge R&D capacities of the household name brands, the smaller manufacturers are still producing very capable, and often far more attractive-looking frames. Here, we take a look at four interesting prototypes from designers based in Europe.

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Dark Owl Parkduro

Fans of the boutique bicycle world may already be familiar with Dark Owl, a one-man outfit designing long-travel high-pivot bikes in Germany. The first bike brought to market by proprietor, Maciej Trojnar, was a steel, idler-equipped 27.5"/26" downhill bike - a niche within a niche, even in 2019. More recently, Maciej has put his efforts into an enduro bike, this time in a more modern configuration, with 27.5" or 29" wheels, front and rear.


The Dark Owl Parkduro is constructed in a way that is, at least conceptually, not dissimilar to how Atherton Bikes' frames are made, with the main tubes inserting into lugs at the headtube and bottom bracket-seat tube mast. That's where the similarities end, however. While Atherton 3D print sleeved lugs from titanium, and join them up with carbon tubes, Maciej is CNC-machining aluminum lugs, and using Reynolds steel tubing. The tubes are bonded to the lugs on their outer face only, and so the lugs need to be extended to maximize the available bonding surface area.

Ultimately, the cost of CNC-machined lugs has increased in recent years, to the point where the cost of the Parkduro frame would be north of what Maciej wants to offer it at. And so, he's looking into lower cost methods of production. One of those options is to use carbon fiber parts, but ones that have been constructed in a way that does not require the production of expensive metal molds. Instead, Maciej is considering laying down the carbon fiber over cores cast out of a low melting point alloy, and autoclaved inside a vacuum bag. In addition to that, he's also considering using titanium tubes, stainless steel, or even carbon tubes. Much is yet to be decided.


Despite some uncertainty as to exactly how the Parkduro will materialize, Maciej has a much better idea of the geometry and kinematic that he'll run with. This virtual high pivot design delivers 160mm of rear wheel travel. The bike seen throughout, with its 27.5" wheels, has a very low BB height of 315mm BB, and a chainstay length of 430mm in its unloaded state. That grows to 445mm at sag, with a further 5-7mm increase before tracking forward toward bottom-out. It has a 78.5° effective seat tube angle at a saddle height of 650mm - the actual SA is 75° and the head angle is an enduro-appropriate 64°.

In contrast to the downhill bike, this one is of course designed with pedaling in mind. To that end, Maciej chose to keep anti-squat north of 100% for as much as 60% travel of the travel in the 50T sprocket of the cassette.


Customers will be able to choose between 27.5" or 29" wheels. On this prototype at least, that's possible by virtue of the swingarm having not one but two mounting points for the rear axle. For the production bike, Maciej plans to offer this feature with replaceable dropouts, such that the swingarm is modular.

There are other key changes to come for the production bike, one of which is a move to a 205mm x 62.5mm trunnion shock, and an increase seat post insertion depth to accommodate a 200mm travel dropper.

Maciej plans to bring three or four sizes to market, with the option of two different swingarm lengths. He's looking to hit a rather reasonable price point of 2,000 EUR for the frame only, and around 2,400 EUR with a high-volume air shock.

More info @darkowlbicycles



GRIN ONE Enduro

Philipp Brunn, an engineer with over 20 years of experience in the automotive industry, has fulfilled a dream of his youth by building the GRIN ONE Enduro. Now undergoing its third round of prototyping, the ONE is a Horst-link aluminum enduro bike, constructed from 7020-T6 aluminum tubes. The frame without shock weighs around 3.2 kg. It is designed around mixed wheels, with a 29" wheel out front and a 27.5" in the rear. Production is due in 2025, when four sizes, with size-specific chainstay lengths, will be available.

The GRIN ONE delivers 160-165mm rear wheel travel (size-dependent), and is designed to run a 160-170mm fork. The geometry chart you see below pertains to the longer travel option. It boasts a modern set of geometry figures, with generous reach (444-511mm), low standover height, and short seat tubes. Chainstay length increases in 5mm increments from size to size.


Geometry of the second prototype (seen here) is non-adjustable. However, the production bike will see the addition of a second mounting position for the shock, by virtue of a flip-chip) that will alter the bottom bracket height (353mm or 348mm), and concomitantly the head tube angle (64.5° or 63.8°), as well as the seat tube angle (78.5° or 77.3°). That lower, slacker geometry position will allow riders to run a lighter 160mm travel fork (like a RockShox Lyrik in place of the 170mm Zeb), without adversely affecting the bike's key angles. The adjustment also brings versatility to the larger frame sizes that, with their longer rear-end, have the clearance for a 29" rear wheel.

The bike looks to have ample seatpost insertion depth, something that will be carried through to the production bike. Philipp says the smaller sizes will comfortably accommodate 180mm dropper seat posts, with the larger ones able to take a 240mm.


The GRIN ONE has a progressive leverage curve, designed for large volume air shocks like the Fox X2, or coil shocks. The starting ratio is high at 3.4, reducing to around 2.35 at bottom-out. The progression is reasonably gradual, and at no point does the leverage rate become regressive. Anti-rise is higher than we see on some other Horst-link bikes of this travel racket, but is also more consistent, sitting at around 80% right the way through the travel, an aspect that should make the bike's behavior reasonably predictable under hard braking. In the climbing gears, anti-squat sits just north of 100% around the sag point, so theoretically the suspension should be neutral under pedal-induced accelerations.

While Philipp is designing and developing his frames near Eberbach and the Bikeländ trails, their manufacturing will take place in Taiwan or Eastern Europe. The projected retail price of the ONE will be somewhere in the region of 2,400 € for the frame without shock. The first bikes are due to hit the market in early 2025.

More info at grin-bikes.de



Scar HFS Enduro

Like many, Stefan Lorenz of Switzerland-based Scar Cycles took up frame building during the pandemic. He started with a hardtail, before swiftly moving on to building an enduro bike. The first was a Pinion Gearbox version of the HFS Enduro you see here. This one, with a traditional derailleur-operated drivetrain, is one of the first frames that Stefan has built for a customer. It has a custom geometry, with an inordinately long headtube of 145mm spec'd as per the customer's request.


The HFS Enduro frame consists of Reynolds 853 tubing, a CNC machined aluminum rocker, with waterjet cut chromoly sheet metal making up the BB cradle. This particular fillet-brazed custom geometry frame weighs in at 4.6 kg, without a shock. Stefan is looking to use thinner sheet metal on future builds to bring the weight down a little.

The bike delivers its 165mm of rear wheel travel via a linkage-driven single-pivot suspension platform, wherein the main pivot is positioned very high. The outcome of that is a 100% rearward rear axle path that sees the chainstay length grow from 440mm to 470mm at bottom-out. In general terms, the linkage is quite similar to that of the V1 Forbidden Druid. Like that bike, the Stefan says the Scar HFS is more ground-hugging in nature than it is playful and poppy.



An 18T idler pulley - larger than most - routes the chain close to that high main pivot to minimize chain growth and the undesirable pedal feedback that would come with that. Stefan tells us this particular pulley is not specifically designed as such - it is in fact the SRAM narrow-wide chainring off an older generation Bosch motor. Another unusual feature of this frame is its use of Cane Creek Forty headset bearings for the main pivot. Stefan says this setup is less vulnerable to the deformations that occur during the fillet brazing process.


With a 170mm travel fork and 145mm headtube, this particular version with 29" wheels has a 64° headtube angle and a 77.5° seat tube angle. The reach is 450mm, the chainstay 440mm (unloaded), and it has a 22mm BB drop.

Stefan is welcoming orders for the HFS Enduro now. A frame, sans shock, will set you back around 4,600 €. In that price is the option for custom geometry. Customers can specify their preferred dimensions and angles for the front triangle, but the swingarm dimensions and pivot locations are fixed.

More info at scarcycles.ch



Rheintritt Ruffy Downcountry Bike

Last but not least, we have a downcountry bike in the mix. This one is a 110-120mm travel flex-pivot affair made by Philipp Mikikis of Rheintritt, based in Germany. The steel frame you see here is a third prototype. It has aluminum inserts for the bearing housings, and an aluminum insert inside the seat tube, to reduce the risk of the seatpost seizing within the tube.

Geometry is fully custom. Philipp has only a few stipulations; a chainstay length no shorter than 445mm, a BB drop of 35mm, and a seat tube angle of around 78°. The one pictured here has 120mm rear wheel travel, paired with a 130mm fork. It has a reach of 490mm, a stack of 655mm, a 445mm chainstay, 78° seat angle and a 65.5° head tube angle.



With a custom-tuned DT SWISS R 535 shock, the Ruffy will sell for around 3,000 € (nickel-plated or copper-plated). That includes custom geometry for the front triangle dimensions only. Orders are being accepted now for delivery in summer 2024. For a 600-700 € surcharge, Philipp will offer a one-week build-it-yourself frame building course, where the customer will weld their own frame using Philipp's facilities.

Rheintritt is also planning to deliver this frameset to customers in a second, rather unusual way; the weld it yourself - at home - option. This is incredibly niche, and will only be a viable option for experienced welders who have a jig at home. Philipp can provide laser-cut sheets of metal, specific to the Ruffy's seat tube and its pivot positions, to work with a regular jig. For around 1,600 € you'll get the laser-cut sheets of metal, the tubes and CNC machined parts, so you can weld it in the comfort of your own workshop.

More info at rheintritt.nrw

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