4 Interesting Prototypes From Emerging European Brands

Feb 1, 2024 at 9:39
by Jessie-May Morgan  
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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.




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.

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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.

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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.

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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


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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.

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Ingo Müller, who also welds for Kavenz, was responsible for fabricating the second batch of GRIN ONE prototypes

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.

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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

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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.

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Scar is the initials of Stefan and family; "S" is for Stefan, "C" is for his wife, Claudia, "A" is for Arne, his son, and "R" is for Ronja, his daughter

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.

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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.

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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

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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.

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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




Author Info:
jessiemaymorgan avatar

Member since Oct 26, 2023
53 articles

100 Comments
  • 87 1
 The progression of quality, finish, and innovation of small-time framebuilders over the past 5 years is really impressive
  • 60 0
 the amount of money it requires without earning any is really impressive as well !
  • 18 2
 @RedBurn: if you count your time as leisure as you love to do it, it is not as mich as you might think :-)
  • 1 0
 @GrinBikes: maybe, but the amount of time and time you need to get good a welding, good at frame alignment, good at suspension design, prototyping and proper tools surely can't be just counted as leisure.
  • 2 0
 @Rudolfo-Balofo: Of course it can, you are welcome to count anything youd like as leisure.
and it all depends on what industry you "work" in, theres plenty of cross over education and experience to be gained.
the time to develop, engineer, design, goes really well with those who work in the engineering field. Time to weld, jig, finish, polish goes hand in hand with those that work in production and fabrication.
If youre already trained and work as a welder, half of the process is already second nature to you, and vice versa if youre a mechanical engineer
  • 3 0
 @onawalk: that's what I did, used the mechanical engineering backgorund and got help on the cnc machining and fabrication side. Love to project, so it is "work" but I count the whole thing as leisure for me.
  • 2 0
 @GrinBikes: Thats amazing for you, Stoked youve found a way to make work, leisure!
  • 35 0
 Hell yeah, Dark Owl. Looking forward to this one.
  • 1 0
 Yeah, bike looks great though I can see people complain about the lack of a dropper (or when they install a dropper, the lack of insertion depth) for an enduro bike. To compensate they got quite a tall seattube so it may not be possible to drop the saddle as low as everyone would like.

As for the lugs, Atherton/Robotbike merely got dual shear lap joints because that's what you need to avoid delamination in the carbon tubes. You don't need that for plain steel tubes (as delamination is not a failure mode there) so obviously they haven't gone through the hassle.
  • 16 0
 If only I could see what the linkage looks like… can’t see shit against the black background
  • 5 0
 And backward. Bring on the feathery hooting
  • 2 2
 @drakefan705: Oh, that may depend on the contrast settings of your screen. It is a very compact linkage with all the pivots in front of the rear wheel.
  • 7 0
 @vinay: I was running the 170mm dropper on this exact bike. Next gen. is going to have unobstructed seat tube, so there will be plenty of room to run 200-240mm droppers without any clearance issues. Cheers!
  • 1 0
 @darkowlbicycles: Thanks for the info. The bike is a beauty! How tall is the seat tube for say a 480mm reach version? To be honest I don't care too much about raising the saddle up high, as long as it can go low Smile .
  • 3 0
 @vinay: Bike in the pic has ~490 reach and bb-top of the seat tube was 450mm
  • 2 0
 @vinay: and it was possible to run longer droppers, but it required flipping the shock upside down, so the resi would be at the bottom.
  • 3 0
 @darkowlbicycles: great choice for cable routing, nicely done!
  • 1 2
 @Mr-Gilsch: Even better if you choose your cable (and hose) color carefully. I think red cables and hoses would go beautifully there. Replacing the hose may be a bit more of a hassle for some, but the outer cable is something that needs to be replaced every now and then anyway. I'm using white cable and hose on a matt green (RAL6001) hardtail as my fork lowers are white too. It is a nice and cheap way to make your bike pretty Smile .

@darkowlbicycles : Well, that sounds perfectly fine to me. Is there a reason to orient the shock as done here? Flipping it around would give you better access to the adjusters too so the only downside I could possibly think of would be whether some bigger ones may hit the downtube under full compression. But doubt this is actually what is going to happen.
  • 4 0
 So, how does aluminium lugs and steel tubes play together? No galvanic corrosion ?
Asking for Shimano..
  • 3 0
 @pakleni: Aluminium parts went through a special chemical treatment (similar to anodisation, but a bit different) before bonding so it doesn't oxidise and produce way greater bonding area. Adhesive I've used is an excelent ionsulator as well. No issues at all after 3 seasons of use. Shimano does not seem to be protected against corrosion in any way, that's why they have issues.
  • 2 0
 @drakefan705: Well yeah, it's a DARK Owl bike.
  • 2 0
 @darkowlbicycles: You should change your company name to 'dark background' Big Grin
  • 4 0
 @DaveRobinson81: Next model will be called DARKERo Big Grin
  • 2 0
 I'm naming my band DARKÖWL
  • 2 0
 @suspended-flesh: With Grim Donut as support act?
  • 1 0
 @vinay: Sure - send us a tape or soundcloud link!
  • 12 0
 The angles/lines of the Grin One frame are really satisfying to look at. My gawd that's a good looking bike. I wonder if the angle of the top tube and seat stay will remain the same on each of the sizes, probably not.
  • 8 0
 Thanks. All sizes are a little different but if you don't know it still looks like one line. The different length chainstays also helped. Cheers
  • 2 0
 @GrinBikes: That puts a grin on my face Smile
  • 1 0
 @BlurredVision: glad it does !!! :-)
  • 2 0
 @GrinBikes: didn't know you could weld 7075?
  • 2 0
 @lenniDK: the welded parts are all 7005, lots of the non welded are 7075. the article is not 100% right on this
  • 9 0
 Thanks GRIN, now I can finally get the Hyper I've been waiting for ssooo long! That is a gorgeous piece of machinery.
  • 8 0
 Thanks. Worling hard to get it into production!!!! :-) Still a long way to go
  • 1 0
 @GrinBikes: dont you fear the seat tube is going to break? every other company will put a gusset up there (except for rheintritt)
  • 3 0
 @tofhami: will be there for the production bike. Didn't look too bad in the FEA simulation for the category 5 fatigue test so we left it away.
  • 1 0
 @GrinBikes: It does look freakin gorgeous. Good prices too!
  • 2 0
 @bishopsmike: still working on the prices so they are not fixed yet but dedinitely don't want it to be the next crazy expensive frame. Also looking at what will be included or if we go for rolling chassis.
  • 1 0
 @Vudu74 I thought it was an alloy version of a 2017 Rocky Mtn Slayer! The silhouette is so similar, same travel and all, just mulleted.
I'm still riding my slayer because it's amazing and one of the nicest looking bikes ever made. I immediately loved the look of this, well done @GrinBikes, it looks awesome! Can't wait to see more.
  • 5 0
 That DarkOwl is like the rebirth of the mid-2000s Rocky Mountain ETSX suspension, which itself felt like a rebirth of a 90s bike with a high, short parallelogram linkage, but for the life of me, I can't remember what bike it was.
  • 7 1
 I miss the days when it was all about DH bikes. There is something about chasing a tenth of a second. Even back in the crude garage build days, it was exciting.
  • 7 1
 The Rheintritt Ruffy is a thing of beauty. Love it. I almost dont care how it rides - that thing would embroil you in hours of conversation anywhere you rode it.
  • 1 0
 I'd love to see it in the copper plated version, I imagine that would be absolutely stunning.
  • 4 0
 @inked-up-metalhead:

You can have a look at my website:
www.rheintritt.nrw/projekt-ruffer
It is not a ruffy, but it is copper plated.
  • 1 0
 @Rheintritt: that is beautiful, I really like the truss top tube.
  • 1 0
 @Rheintritt: The bikes look great. Are there any reviews out on the Ruffy?
  • 3 0
 @jessiemaymorgan Wait a minute. Regarding the Grin One: Did The guy really say the bike was constructed from Al 7075-T6 tubes? Like actually welded Al 7075? Because consensus is that that's pretty much not possible at this point. Although there are some people here and there who claim they pulled it of via usage of a special titanium-carbide filler.

Would be pretty cool if true, because carbon would basically become obsolete as an mtb frame material.
  • 2 0
 I guess the chainstays and maybe the rocker is made of 7075 since they are machined.
  • 1 0
 Yes you are right. Welded parts are not 7075. Used it for rocker, bolts, ... Havent't seen anyone using 7075 in welded structures.
  • 6 0
 Only come here for the expected lack of cable tourism.
  • 6 0
 Love that they are all metal!!!
  • 13 8
 I've grown to loath the term Downcountry.
  • 4 0
 Can we make the pictures of the Dark Owl a little...Darker? I can almost see the linkage.
  • 7 0
 Here You go mate, better lighting, couldn't post them in the article tho:

www.pinkbike.com/u/darkowlbicycles/album/Parkduro-V2
  • 4 0
 Gonna order mine in vantablack and only ride it at night so I never know
  • 2 0
 @darkowlbicycles: wow, great headtube badge! It really pops in golden color on the black frame.
  • 1 0
 It's pretty cool that you can buy the Ruffy as a box of tubes, and then weld them together yourself. I suck at welding, but I'm pretty good at gluing stuff. I wonder if Atherton would send me a box of tubes and lugs and a bottle of glue for cheap.
  • 3 0
 The Dark Owl Parkduro is the closest to my dream of a Turner DHR resurrection as an up-to-date all mountain/trail bike.
  • 4 0
 Grin One is just gorgeous!
  • 3 0
 The Ruffy is intriguing to me, welding my own bike with custom geo would be amazing.
  • 3 0
 I really want to look at the Parkduro bike. But a dark background… c’mon.
  • 3 0
 2 thumbs up for all the small builders doing their thing, keep it coming PB.
  • 3 0
 Dark (m)owl looks sick ! You can feel the force in it !
  • 3 0
 Love Horst Link Suspension, the Grin looks stunning!
  • 3 0
 That Grin ONE Enduro is absolutely beautiful
  • 3 0
 Very beautiful bikes. Thanks for passionate people building these things!
  • 1 0
 @jessiemaymorgan Dammit! I even put a prototype label on the frame, but apparently it's not interesting enough.. :-( ;-) www.pinkbike.com/photo/25832700
  • 3 0
 Dark Owl, that's a cool name for sure!
  • 1 1
 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°. Then it's not fully custom..
  • 2 0
 That's a funny looking Reeb SST at the end
  • 1 0
 HaHa and the Reeb looks like a Swarf Contour
So What Wink after all it's am MTB

The Ruffy was created by the "Stahl Rudel" of the MTB News Forum
www.mtb-news.de/news/craft-bike-days-2023-rheintritt-ruffy
  • 5 2
 holy molly flexy Ruffy
  • 6 0
 Not as flexy as you would expect. We have tried to break the bikes with 100+ kg riders for quite a long time. Smile
  • 2 0
 Im digging those headset bearings for the main pivot on the Scar
  • 1 0
 Copper plate option on the Ruffy - very nice. Would love to have a frame copper plated one day.
  • 2 0
 Finally some affordable bikes!
  • 2 0
 A grinning dark owl with a scar named rheintritt ruffy
  • 1 0
 That downcountry bike is sick. How is it a custom steel Spur costs the same as an actual Spur?
  • 2 0
 I feel guilty now with my wife sitting beside me. Pure bike porn.
  • 2 0
 Dark owl Parkduro. The bike we all need. Best brand name ever.
  • 1 0
 The brazed together tubes and sheets, love it, nice work!
  • 1 0
 ..and rides even better ☺️
  • 1 0
 "How long do you want the chain?"
"Yes"
  • 1 0
 Single chain here \m/ , Cheers!
  • 1 0
 @darkowlbicycles: Is it? Looks longer on pics, maybe the rear mech cage position makes that
  • 1 0
 That's some steerer tube poking atop the Dark Owl.
  • 1 0
 That was fixed later on! Check out the newer version on our instagram @darkowlbicycles , Cheers!
  • 2 0
 @darkowlbicycles: i love the fact you are hear, reading and discussing your product. Kudos.
  • 1 0
 They had me a copper plating
  • 2 2
 I dig the handmade frames.. gumwall tires are for the Castro SF sissy types. F'n ugly..
  • 1 0
 That Grip One is absolutely stunning.
  • 1 0
 That Grin is a great looking thing!
  • 2 0
 Dope
  • 3 5
 Something about those twiggy rear triangles I don't trust
  • 3 0
 They're supposed to flex for the suspension linkage to work so I wouldn't trust it if they were thicker.







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