This Aluminum Gearbox Hardtail Has No Seat Stays

Oct 28, 2020
by James Smurthwaite  

When Karl Groetzinger set out to design his first fully built frame design, he had one goal in mind - make it different from everything out there. Karl first began designing bikes 10 years ago, but didn't have the facilities to build them. Now, as a 26-year-old, he's finished his degree in mechanical engineering at the University of Stuttgart, taught himself aluminum welding, and has been able to make his visions come to life.

It's another bike to add to the list of wild lockdown projects coming out of Europe this year including the fully European Crossworx 29, Swithcraft's British Inspired trail full suspension trail bike and the mighty Moorhuhn but this one is surely the most visually striking yet.

The name of the project is 'прототип', literally Russian for 'prototype', and it's an aluminum, gearbox-equipped hardtail with one big difference: there are no seat stays. We've seen plenty of full-suspension bikes with a single swing arm (Orange's classic design and the Polygon Xquare One come to mind) but very rarely have we seen this style design in a hardtail.
Details

Frame Material Aluminium
Intended Use All Mountain
Intended Travel 140-150mm fork
Wheel Size: 27.5" front/rear
Frame Size: Large
Geometry: N/A
Price: One-off frame, not for sale.
More info: @karlgroetzinger


While most manufacturers use metal tubes for the chainstays and join these to a gearbox housing with a weld, Karl uses folded sheet metal all the way along the chainstay and into the BB/mount for the gearbox.

The first question anyone will surely ask is, "Won't that break?" Well, that was the big challenge for Karl; if he was going to make something unique he was going to make sure it worked too. By using sheet metal to integrate the Pinion box, he was able to spread the loads and not have a weak join between the stays and the BB area. Alongside this unique construction method, he's also making sure the area around the gearbox and the chainstays have plenty of metal keeping everything pointing the way it should be. The folded metal cuboids he has used for the stays are 50x20mm in profile plus have a 3mm wall thickness thick, which is about twice the thickness of conventional aluminum tubes used on mountain bike chainstays.

Karl works at the Institute for Metal Forming Technology in Stuttgart and used the 500 ton Schuler knuckle joint servo press in the background to form the Pinion housing.

To prove his design, Karl has been using a frame-mounted strain gauge and a 3D scanner to measure how the lack of a seat stay affects the bike. He has concluded that there are "only slight plastic deformations" but this is something he intends to remedy in the next model by using an even stronger 7000 series aluminum alloy, which has an almost 2 times higher yield stress. Also on the next version will be a belt drive instead of a chain and potentially a gusset between the seat tube and top tube.

The attention to detail is incredible, including machining these brake mounts after welding to ensure they were perfectly aligned.


Karl is using a strain gauge with measuring sensors on the cantilever to learn more about his design and how it can be improved for version 2.

So what will the disadvantages of this design? Well, the extra material needed to reinforce the chainstays doesn't come without a weight penalty. The frame currently weighs 2.5 kg (5.5 lb), which puts it about 200 grams (0.5 lb) heavier than, for example, Nicolai's Argon AM Pinion. The full прототип build Karl has selected here tips the scales at around 15kg (33lb). We're also not yet sure how the design will react to torsional forces as the bike is cornered hard. Really though, none of that matters. This wasn't a performance-driven design - Karl set out to create a bike, unlike any that had been seen before and it only takes one look to know that he has succeeded.

Karl is gaining further insight on the physics of the bike from a GOM 3D scanner.

The bike is currently a one-off design exercise although Karl has been surprised at the amount of interest and could consider making a production run if it continues. He currently has designed the frame around his own large proportions with the intention of fitting it with a 140-150mm fork and using it as an all-mountain bike. No geometry info is currently available. The best way to keep up with the project is to follow Karl on Instagram.




211 Comments

  • 623 4
 Weird flex but ok
  • 71 1
 5/7
  • 56 8
 Sounds like my kids at the dinner table.
  • 138 66
 @Tearsforgears:
OK Boomer
  • 13 0
 @browner: A perfect score!
  • 32 0
 This is the best use of this one-liner I have seen. Well done sir.
  • 76 17
 "Karl is using a strain gauge with measuring sensors on the cantilever to learn more about his design and how it can be improved for version 2."

Uh... put seat stays on it.
  • 28 3
 @colincolin: Who disabled this kid's screen time?
  • 21 47
flag me2menow (Oct 28, 2020 at 11:59) (Below Threshold)
 @colincolin: the boomers are getting real aggressive with that downvote button
  • 2 3
 Drop it like its hot
  • 1 0
 Lolllllllll
  • 2 1
 Gah. Fat fingers
  • 1 0
 @browner: With rice
  • 1 0
 @colincolin: No Boomer has kids that talk like that because a Boomer's kids are in their 30's and 40s now.
  • 2 0
 @CaptainSnappy: Millennial here. We talk like this.
  • 130 0
 Do no top tube and a lefty fork next!
  • 44 4
 so basically a moped
  • 14 0
 Replace the downtube with the old slingshot technology!
  • 119 1
 Looks snappy
  • 23 20
 In more ways than one!
  • 1 13
flag DirtbagMatt (Oct 28, 2020 at 11:09) (Below Threshold)
 @SJP: LOL!!
  • 16 0
 @SJP: Thanks for explaining the joke bro
  • 1 0
 @SJP: ????????????????????????????????????????????????????????????????????????????????
  • 2 0
 @SJP: the ??? Are supposed to be laugh emojis. Classic response
  • 86 2
 Looks very cool! And don’t forget it’s an engineering project to learn new stuff AND a bike. Not a production thing made to make $$$.

Great work!
  • 9 17
flag bogey (Oct 28, 2020 at 14:38) (Below Threshold)
 From what's been presented, I see this as a cool fabrication project and not an engineering project. I'm not saying that this wasn't done but I don't see it (design requirements, modeling, FMEA, etc).
  • 8 4
 there is no engineering problem that this solves. It certainly creates some though. B-b-b-b-but muh german engineering!!!
  • 84 2
 look ma, no seatstays
  • 71 0
 @Mikekazimer huck to flat test this
  • 5 0
 America
  • 3 7
flag stiingya (Oct 28, 2020 at 16:49) (Below Threshold)
 @jaybird951: the Beautiful....
  • 50 0
 Seat Stay if you've got to go away
Don't think I could take the pain (Stay now)
Won't you stay another day? (Stay now)
Oh don't leave me alone in this pit
Don't you say it's the final sit (Stay now)
Won't you stay another day? (Stay now)
  • 2 0
 haha well done
  • 8 0
 sorry - - can you help me out with the tune here?
  • 2 0
 @robokfc: E17, Stay.
  • 12 0
 There’s gonna be a whole world outside of the uk and a whole generation outside of yours (I’m assuming you’re mid 30’s) that haven’t got a scooby what you’re on about. Not me though, I love your work.
  • 12 0
 @pimpin-gimp: Not to mention the people that are now wondering why you're referencing a cartoon Great Dane..
  • 2 0
 @w0dge: OK, maybe you can help me out with how to pronounce that name in english.
  • 2 0
 @RayDolor: Say it East Seventeen. It's the London postcode where they are (were?) from.
The song was a big Christmas UK hit in the mid 90s. I know it is objectively bad but I still kind of love it
  • 6 0
 @RayDolor: Worth looking up them just to read the story of how one of them ran himself over with his own car after eating too many jacket potatoes. Yep.
  • 1 0
 @lacuna: PMSL Just spat coffee at the jacket potato part!
  • 1 0
 @lacuna: I heard he got high snorting Smash
  • 42 1
 Looks cute, might break later.
  • 3 2
 good comment, my thoughts as well.
  • 28 0
 I love the just because it's different I will do it attitude ...it from that that the one in a hundred great ideas come from. This is a great example of somebody trying to learn and experiment. Kudos!!!
  • 31 0
 I'm betting that in less than 10 rides it has no chain stays either.
  • 31 3
 First improvement: seatstays
  • 3 1
 Actually it would be nice to see it with belt instead of chain and with some suspension travel too.
  • 3 1
 @romkaind: It the chainstays were steel, it would act like a spring, it wouldnt move more than 5mm but it would take the edge off. And I agree, should have used a belt instead of a chain, especially if he wanted to build something different.
  • 28 5
 I appreciate thinking outside the box at the scale of both the frame and detail, in both design and fabrication (as with the post-weld machining). But design that is admittedly not performance-driven and different for the sake of different seems ... frivolous? I dont know, maybe something unexpected and useful will come of it.
  • 5 4
 Agreed, however; this is a hardtail. Ironically though, I would assume the byproduct of the paradigm breaking design, would actually be better trail compliance. After all, the rear stays would act similar to that of a leaf spring, even if its very minor.
Reality is, the market for hardtails is very niche, and ultimately I believe this design would actually gain some popularity among that crowd.
  • 3 2
 @jomacba: The stays act as cantilever beams and not leaf springs. Leaf springs have damping built into their design whereas this doesn't. This design is also horrible under torsional loading.
  • 3 3
 @bogey: No I fully understand the concept, however even a cantilevered structure will show more deflection compared to a supported structure.
Yes I will agree this design will also have defletion under torsional loading.
Reality is this, in my opinion hardtails are best suited for dirt jumping. They will never measure up to a proper full suspention design, no matter now you stack it.
  • 1 2
 Trek has been quite successful with this approach over the last decade....
  • 19 1
 "he had one goal in mind - make it different from everything out there."

Done. But why? Is this a sensibel goal.
  • 5 5
 It is a just a different approach. The traditional triangles are designed around the idea that it is lighter to design a truss structure where members are loaded by tension (which is most stable) and obviously some by compression (because you need those too or everything would just collapse). Loading a member by bending isn't ideal as it requires a bigger moment of inertia (hence a larger cross section, hence a larger volume, which favors materials with a lower density like aluminium). You'd do it if it gives you advantages like having more room to move for a rider. Which is why some designs (especially a decade ago) had a single large diameter beam instead of a top and downtube. Especially for downhill bikes or for aerodynamic reasons on time trials bikes. It seems brands are kind of moving away from that and go with separate tubes again. So yeah, we've been seeing it for front triangles. Not sure what's to gain in the rear triangle of a hardtail though. It is not like you've got more room to move as there is still a wheel. Rocky Mountain did it for a while on a full suspension bike yet even Orange seems to be moving away from it with their more recent bikes.

As I don't sit much on my bike but do value a low top tube, I'd actually be more interested if they'd make one with a bulky downtube (like the older Orange bikes), remove the top tube and do with a super short seattube (so that indeed you'd have a low monocoque rear "triangle" too). That would make actually be fun. But removing the seatstay but still have a conventionally high top tube, I don't see what you're gaining there other than maybe some mud clearance and maybe easier transportation with the rear wheel removed.
  • 2 1
 @vinay: FYI: a wheel keeps it toghether by tensil forces
PS - I've never hited on the seat stays!
  • 3 0
 @TDMAN: Yeah but I meant to say that with the wheel staying as it is, removing the seat stays doesn't give you more room to move around as a rider. Removing the top tube does, removing a rear rack or fender does, but the conventional chainstay on a hardtail doesn't. So yeah indeed, if you hit something it'd be the tire, never the seatstay.
  • 1 0
 He's a goth?
  • 6 1
 This bike is in its natural element on an engineer's CV. Elsewhere? Who knows and who cares?
  • 1 0
 @TDMAN: ... while the rim is being compressed.
  • 1 1
 @theobviousfaker: Due to geometry, a Rim won't suffer compression (meaning forces normal to the neutral axis)

I would say, the rim is loaded like a beam, unrestricted, and that will translate into compression and tensil force accross it's walls
  • 1 1
 @TDMAN: Interesting. I'd be inclined to think that due to the spokes pointing towards the hub (for a radially spoked wheel) would pull the rim parts together hence compress the rim in normal direction. Now of course we don't ride radially spoked wheels so it may imply that it depends on which section of rim you're looking at. But net I'd say the spokes still pull towards the center hence compress the rim in normal direction. I'd view it as the opposite of a wooded wagon wheel (where wooden spokes are loaded under compression) so you'd need a steel strip around the circumference to pull the rim together, which implies the rim itself (including the steel strip) is loaded under tension.
  • 16 0
 No surprise coming from Stuttgart. They have one of the craziest Formula SAE teams in the world. Seeing their car compete at Michigan Raceway in 2018 was insane. We couldn't even get ours running in time lolol.
  • 1 0
 They were crazy back in ‘08 & ‘09 too man. Them, Tu Graz and Univ of Western Australia were stunning cars that exuded F1 budgets and technology.
  • 12 0
 Access to all that metal forming equipment, and each chainstay is made from 4 pieces and nearly 2 metres of welding? That part would have massively benefitted from being formed, it would be relatively easy to halve the amount of weld needed.
  • 13 0
 I see room for at least 4 water bottles on this thing
  • 10 0
 Feels weird to only see shots of the bike from the non drive side. Almost like they’re hiding something haha.
Curious to see how strange it looks from the other side!
  • 15 0
 @HMBA106 Just uploaded one here for you: www.pinkbike.com/photo/19639403
  • 4 2
 @jamessmurthwaite: why does a hardtail need the idler/tensioner set up? does it flex that much or is it an all-in-one gearbox system that has it incorporated?
  • 7 0
 @AyJayDoubleyou: It would have to have sliding drop-outs if it did not have the tensioner.
  • 1 2
 @AyJayDoubleyou: That's definitely a part from pinion but I'm not sure why he's used it here...
  • 2 0
 @notthatfast: Because without sliding drop-outs, there's no way to adjust the chain tension.
  • 1 1
 @JVance: Yeah I guess... I'd have preferred to run a sliding dropout to get optimal chain tension rather than add a tensioner as they tend to work less well in my experience but I guess he wanted to preserve a certain chainstay length instead...?
  • 1 0
 @notthatfast: this guy obviously wasn't prioritizing chainstay length (or any other performance characteristic for that matter). The yoke area is so overbuilt that those stays must be 19". Look how far the bb is from the tire
  • 12 5
 Designs like this have been around for over a century. It’s a structurally inferior way to build a bike frame. It’s not innovation, just doing something differently for the hell of it. It on no way advances or improves the bicycle.
  • 2 1
 Agree, L=lots of road/track bikes used similar concept, however as history shown it is not something that brings benefits other than out of the box look (in this case with all - word look )
  • 5 0
 @nickmalysh: No seat stay may bring an aerodynamic advantage on time trial bike (see Diamondbak Andean), but not on an MTB.
  • 2 0
 @Will-narayan Agree on that, however I doubt that was the Goal with this "Прототип"
  • 6 1
 It's strange after all that borrowed equipment and ten years of youth full dreaming , how can a statement be made that performance or the fact that the design even works doesn't matter, he still succeeded? REALLY ? Sorry I still live in REALVILLE !
  • 7 3
 Lots of haters but I don't see you MF'ers welding a beautiful bike like this. Also as an engineer, I respect the innovation and new ideas. Frame flex as part of the suspension system is coming for sure and this could easily be a step toward the hard tails of the future. Great work Karl, way to be super thorough with your analystics. Keep at it bro!
  • 3 0
 I'm not an engineer so I won't even try to chime in regarding performance or durability, but I do think it's actually kind of an ugly bike. The transition from slim round tubing in the front to large boxy welded sheet metal is jarring and makes the bike look very cobbled together IMO. I feel like if the focus wasn't on performance, than aesthetics should have been more of a concern.
  • 3 2
 This isn’t a production bien with beautifully hydroformed tubing. Buddy just welded together a bunch of straight pipes and sheet metal. A production version would look much more refined as you wish.
  • 1 1
 Production bike*
  • 3 1
 Lots of other people saying do a Lefty build next time, but I think it can be taken one step further. Lefty fork, right side only “chain”stay. Asymmetric as can be. Rear brakes might have to be rim-only, but I’m sure there’s some other way around that issue!
  • 1 0
 @Austink: daaaang that's a sweet bike.
  • 1 0
 @sjma: yeah the builder does some absolutely wild stuff. Check out his other work for more craziness.
  • 2 0
 Yeah I don't get it... He says that if he was going to create something unique it had to work. I mean yeah, it's a bicycle that goes and stops, but I'm not sure it would actually 'work' on the trail as a modern mountain bike. That said, I'd love to be proven wrong.
  • 4 0
 I’m a big fan of aluminum frames, but I have to wonder if carbon is not a better material if you are trying to engineer flex in one plane.
  • 4 1
 Damn usually I am not a fan of hardtails but i find it beautiful ! The lack of seatstays bring something really unique to the overall design!
  • 1 0
 The only advantage I can see is that you can use a belt drive without the need of a splitable rear triangle (solvable problem). Otherwise structurally it's an absolutely inferior design compared to the traditional geometry. Just plain wrong in every performance aspect.
  • 1 0
 Just a thought. Back in the day there was a discussion about best alloys to use for suspension due to Stratos suspension bending stanchions on their forks, these were 6061. They ruled out using 7000series alloy, while it could resist flex and fatigue over time, it was more brittle and likely to snap without notice. Sometimes a bit if flex is a good thing.
  • 1 0
 Well, that's dumb. But, on the bright side, he had to overbuild the chainstay-yoke/bb area so much that the chainstays ended up being 19" long, so it's got that going for it at least.

And he's using a racing ralph on the front with his fox 36, so you just know he's really putting this thing through the paces.
  • 1 0
 I love that you are exploring this option Karl! And Pinion with belt drive sounds awesome! I suppose this isn't too far off from a softail concept that Litespeed came out with in the 90s. I believe Moots has a YBB bikepacking rig right now. Also, not sure on availability of titanium sheet metal or the workability, but you'd get more compliance out of it and would be far stronger than aluminum... infinite fatigue life as well. I hope you keep going with your research; I'm interested where you end up with this. Thanks for sharing!
  • 1 0
 Back in my day you had to draw your own solid models for your mock ups, no 3d scanner. And dont even get me started on paper lol. Boy do I feel old. I need some snow and a driveway to shovel. Bloody nice bike though, comrade! Just an idea, but what about internal gussets or like a lattice type framework for the chainstays?
  • 2 0
 What are they teaching engineers these days when the first thing they want to do when they get out of school is to avoid building a triangle for an application that calls for a triangle?
  • 1 0
 Meh.

This design could be used like a softtail, but aluminum is the wrong material for that. He has to add so much material to keep it from yielding (which puts the material in a low-cycle fatigue range where it will fail after tens of thousands of cycles instead of a million-plus where it should be) that there's no weight savings. Yes, 7000-series should help, but if that was the goal, then he should just go to 6/4 Ti and get double the strength of the 7000-series AND still likely get better ductility and fatigue all at a lower weight.

If it does have that vertical compliance--which would be good--I doubt it would have torsional stiffness, meaning you can probably watch the top of the back wheel move excessively right/left, not to mention lateral bending like a fish tail. I can't believe this thing handles well at all except for the mildest of riding.

So for a cruiser--sure, why not. For a mountain bike? I wouldn't bother.
  • 4 0
 More to the point, it has no dropper post
  • 4 0
 but if you want to eliminate chain slap you need to get rid of chain stays
  • 4 0
 Should have gone with the high-pivot and idler.
  • 1 1
 Imagine someone did this with a full sus. They could put the chain inside the swing arm too and lubricate it for zero maintenance.

I know this has never been done before because PB says... pretty sure millard racing might disagree though. Smile
Maybe a HT is more complicated to do this with than a FS, who knows. But the millard bike was raced and never snapped, even though the forces would be reduced due to the suspension in theory, or are they higher as you go faster...
  • 2 0
 So much effort and not belt driven? Start all over again and do it right next time, and after that give it some suspesion in the rear.
  • 4 0
 Holy fatigue failure, batman!
  • 3 0
 The german name of the bike should be "Sollbruchstelle" :-)
I like the design, looks really cool.
  • 2 0
 That is actually an amazing idea!
  • 1 1
 Super cool. I love seeing people push the boundaries. I imagine something like this but made of carbon. You could get a softtail and engineer the chainstays to act like a leaf spring. I think v1 actually sounds like more fun to ride than v2, provided the amount of flex isn't crazy noodly.
  • 1 0
 Ghost has a new design for their Lector, it has a leaf spring style to the rear triangle. Ghost lector SF
  • 1 0
 @OugaBooga: that bike is high on my list of bikes to try. I love seeing unique ideas.
  • 1 0
 By all means make something that looks different even if we all know it makes no sense. You know what might weigh the same and relieve all the need for extra material for strength..... A pivot and a shock.
  • 2 0
 "...strain gauges..." we have too many, find a use for them. Don't care how backwards the idea. Trimble. I'm sorry but this one gets five face palms, sorry, sorry.
  • 3 0
 Disappointed in the lack of lefty fork.
  • 1 1
 Not hardtail or gear box, but for those tripping out about the lack of seat stay I can think of two bikes off the top of my head with no seat stays. Chumba F5 and Rocky Mountain RMX.
  • 2 1
 see also every moto bike.
  • 1 0
 also reminds me of the 1992 Trek 9500
  • 3 0
 ПРОТОТИП.. Ok... БЕЗНОГNM comes to mind
  • 2 0
 More like БЕЗПЕРЬВ
  • 2 0
 Love the way it looks but I know I’d turn that flexing swing arm into a snapped swing arm
  • 2 1
 Probably less likely to fail than a long travel single crown fork. It does look like a failure waiting to happen but you have to think an engineer has figured it out to a certain extent.
  • 3 0
 Paging Jason Lucas... paging Jason Lucas...
  • 3 0
 looks like KUVALDA is finaly imploed by rusnano
  • 2 0
 Came just to browse the pictures, saw the machinery, saw a bike hooked up to a computer, must be German. Sure enough.
  • 1 2
 iam courius if the welds will be better/look better on the finished product. having so many big lines without smoothwelding or filling, i wont buy it. maybe have the 2.0 version with an cnc rear end? Smile

but cool design ! looks like a mix of nicolai and zonenschein
  • 4 3
 That's funny, I really like the more industrial looking welded aluminum bikes with straight tubes and big welds. It makes me super sad when companies use a bunch of hydroforming and smooth out their welds so their alloy bikes look like carbon. To each his own I guess!
  • 1 0
 @gibspaulding: Both is nice, i really like a nicolai, intense or ancilotti. but come on, you cant tell me this looks good to you?!
  • 2 0
 looks like a full suspension frame design ! but without the rear suspension it looks... snappy..
  • 2 0
 Fcuk it, why not swap fhe down tube for a bit of steel rope whilst you at it
  • 2 1
 Who cares about NO seat stay....
I wanna know more about the gearbox !! Gearboxes = the NEXT dimension beyond AXS wireless shifting (made from titanium Smile
  • 1 0
 140-150 Hardtail with a 120mm Stem ? wild. . . .but although the fork says something different this thin is maybe more of a gravel grinder than a shredder . . .
  • 2 0
 Some people definitely know how to play.
  • 2 1
 I think this bike looks rad! After bending my derailleur on my DH bike this weekend I am wanting a gearbox so badly!!
  • 2 0
 I love the look, and outside the “box” thinking
  • 1 0
 I’m glad someone took that napkin drawing everyone has drawn and made it into reality.
  • 2 0
 He's stacking dinner plates not dimes in that welding...
  • 2 0
 I can't take an MTB seriously without a dropper now.
  • 1 0
 Looks like a product from Grimm. Wonder if this will be there second bike? Grimm Cruller?
  • 2 0
 Can’t wait to see the huck-to-flat test.
  • 1 0
 Just a few huck to flatt and it wont have annymore chain stay either. Dosen't have water bottle cage and dropper either...
  • 2 0
 Orange Bikes called... they want their chainstays back
  • 1 0
 this is secretly the next Orange Crush
  • 1 0
 With this design there is no need to cut the seat stay to install a belt drive.
  • 1 0
 Just need to replace the frame after ever few rides.
  • 2 0
 I’m gonna give him props just for not putting a motor on it.
  • 2 0
 What’s the warranty like?
  • 2 0
 No seat stays and probably no chain stays if ridden hard
  • 1 1
 mount the seat from an extension of the down tube....eliminate the seat tube and the top tube and put in a pull shock on the down tube against a single pivot.
  • 2 0
 Tribute to RM's Thrust Link circa 2003?
  • 2 0
 anyone seen a lahar am i right wyn masters
  • 2 0
 Ahhhhh thats what it was reminding me off!
  • 2 0
 The only fork allowed on this bike is a Lefty.
  • 1 0
 Cool Hardtail! Please use tension/flex adjustable steel wires for seatstays on V2.
  • 3 0
 NOPE!
  • 1 0
 I’m not sure that this kids ‘idea’ needed sharing. I like reading about homemade stuff but it’s got to be useful.
  • 1 0
 OK, Pinkbike are here for the big feature on our amazing new bike, pass me that ugly ass firebrick to prop it up will ya...
  • 1 0
 Great idea for a road or gravel bike. I wouldn't ride a mountain bike without rear suspension.
  • 1 0
 Whilst I understand that only sith deal in absolutes, I would 100% break that.
  • 2 0
 Someone needs to put a LEFTY "fork" on this bad boy
  • 1 0
 This bike is sick I would one hundred percent buy this bike. One question why is the derailur in the front
  • 1 0
 sick project sick bike but should have went to school for welding ouf, overheating and puddles
  • 1 0
 Kinda like Lefty forks - it solves a problem that doesn't exist.
  • 1 1
 You must not know anything about lefty's. The lightest forks with the least amount of flex and best small bump compliance.
  • 1 0
 Looks cool but i wouldn't like to case anything bad with that!!!
  • 1 0
 F**k a seat stay, all my homies riding прототип
  • 1 0
 Looks like a HT version of arbr rb2....which I really like the look of.
  • 1 0
 Gonna be a snappy experience.
  • 1 0
 Why? What is the advantage?
  • 1 0
 Aerodynamics and you don't have to clean mud off the seat stays?
  • 3 0
 He would have never gotten on PB if it had seatstays.
  • 1 0
 This looks like a good idea, I wonder how a longterm test would be like
  • 1 0
 Just because something can be done, it doesn't mean etc.
  • 1 0
 Now thats some bike nerd stuff right thur
  • 2 0
 Oh hey, it's 2003 again.
  • 1 0
 2024 Super Caliber with 80mm travel
  • 1 0
 I wish i was smart so I could do something cool like this. )-:
  • 2 0
 No thanks
  • 2 0
 ALUMINIUM
  • 1 0
 I think it's more a soft tail than a hard tail...
  • 1 0
 Whats is the logic behind those 220mm rotors
  • 1 0
 I felt the back tire knock me in the head the moment I saw this.
  • 1 0
 and maybe it needs a Allsop Softride to complete the design.
  • 2 1
 Why is the name of the bike written in Russian? BTW it says Prototype.
  • 1 0
 i thnk i need to ride, it to believe it ! looks good though
  • 2 0
 Well. Its gunna snap.
  • 1 0
 He said strain gauge.????
  • 1 0
 Looks fast bet its snappy out the gate..
  • 1 0
 Here’s a thought..... pus some seat stays on there
  • 1 0
 When a hardtail isn't hard enough
  • 1 0
 This bike screams HUCK ME!
  • 1 0
 Soon is just gonna be dudes running holding two wheels.
  • 1 0
 Looks like a Brompton
  • 1 1
 YES! Looks like a Brompton, only looking at the wheels! "TAACCHTT* ----> PALM IN THE FACE"
  • 1 2
 I know I'm probably the first, but is it weird to have an erection while at a computer?
  • 1 0
 For some, it’s weird not to...
  • 1 0
 Looks like a Strider!
  • 1 0
 No pics of drive side?
  • 1 0
 What the blyad' is this?
  • 2 3
 Damn kids these days making awesome fucking bikes!
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