Bike Check & Interview: Evan Turpen's High Pivot Steel Beauty

Jun 22, 2020 at 7:37
by Dan Roberts  





Despite the flurry of home-crafted style bikes recently, we're still as keen as ever to see more. So, when Evan Turpen got in touch with details of his project we were of course interested.

But after only a couple of emails back and forth there were mentions of patents, performance drivers, high pivots and steel, which got our ears really pricked up. And with a visual taster of the bike it was clear that this was a home build on a slightly different level.

Delving deeper into the bike provided a cauldron full of information and insight into how this ex-racer took a simple note on a phone and made it a reality of a rideable bike, with all the challenges along the way.

This is a closer look at Evan Turpen's custom high-pivot steel beauty.





Bike Check Evan Turpen - Bike
Details
Rider Height: 5’ 9.5" / 177cm
Rider Weight: 180lb / 81.6kg
Hometown: Aptos, California, USA
Model: Prototype
Frame Size: Custom, but considered an L by today's geometry
Wheel Size: 29"
Travel: 140mm or 164mm
Suspension System: High single pivot with idler pulley. Linkage driven shock
Development Time: 17 months (developing & fabricating)
Fabricators: Evan Turpen & John Caletti


Bike Check Evan Turpen - Bike





History

When did you first get into bikes?


2000. I was inspired by a friend who had recently gotten into mountain biking. He had a beautiful Santa Cruz Bullit that I couldn't stop lusting after, especially after riding it around for the first time. As a money-less, job-less teenager there was no way I could afford such a nice bike, so instead I decided to dust off an oldie but goodie that had been sitting dormant for years. It was a Red Cannondale CAAD3 hardtail that was a Christmas present from my parents. About as far as you could get from a Bullit with its cantilever rim brakes, flat bars, and triple chainring, but I proceeded to ride the crap out of that thing! From that day on, mountain biking was all I wanted to do, and it was all that I did. I was obsessed.


When did you first start racing? And what discipline?


In 2001 I started racing downhill at a local race series. Somehow I managed to win the first race I entered as a junior and I was hooked on racing from that point on.


Views: 19,088    Faves: 359    Comments: 53



How long did you race for? Which disciplines did you race throughout your career and why?


Racing downhill, dual slalom, and the occasional 4-cross race was my life from 2001 to 2011. I raced because it gave me meaning and focus and despite the stress it was a hell of a lot of fun! As a privateer I never made any money racing bikes and struggled with coming up short results and sponsorship-wise. In 2012 I ran out of steam and took a break from racing to work on a small lift-accessed bike park in the Sierra Mountains. While building and maintaining trails at the park I decided to give enduro racing a go and signed up to race the Trans Provence later that year. I had no idea what I was getting into, but the concept of blind racing in epic locations was rad. Since then I've raced quite a few more enduro races and I will continue to race enduro for as long as I can. Don't get me wrong though, I still have a soft spot for downhill and dual slalom. I'm turning 35 this year, but I wouldn't say I won't race a downhill bike ever again.


How did your riding and racing background influence you into creating your own bike?


Through racing I was always very focused on trying to have the best equipment possible. Ultimately, the realization came to me that nobody makes the perfect bike. Most companies are limited by none other than themselves. Engineers have to make products fit into a particular box for marketing and sales reasons and therefore are unable to think outside the box. The design of this bike wasn't limited. It was a clean slate aimed at getting the most performance possible out of a bike with absolutely no obligations to anyone but myself.


What do you do aside from bike riding and making bikes? What’s your current profession?


My current professional title is "unemployed". I am actually a professional bike mechanic by trade. Up until October of last year I was the lead mechanic at a local shop. When I left the shop, I took out a $20,000 loan to help cover living expenses and give me the time I needed to focus on the bike design and fabrication. It was a bit of a risk for me as I had never made a bike before and didn't know if it would pay off, but after riding the first prototype I am 100% confident that this was the right decision.


Bike Check Evan Turpen - Action





Development

When did you first start developing this bike?


The bike started as a note in my cell phone in August of 2018. It was basically a wish list of characteristics and features that I thought would make the "perfect" bike.


You mentioned that you’re not an engineer. Which hurdles did you have to overcome and which areas do you feel you've learned the most in to get to the end goal of a physical bike?


The first major hurdle was designing the bike in 3-D since I didn't have access to or the skills to use 3-D design software. I eventually managed to get a student license of Creo Parametric 3-D design software. I took an online Creo class and within 3 weeks had learned enough to have a very rough 3-D assembly. It was a proud moment to actually cycle through the travel to check clearances on the frame in the computer.

The next big hurdle was my lack of engineering experience as it relates to design. I shared the design of the bike with a friend who's an engineer and he suggested that I look at the forces generated on the links and frame using FEA (Finite Element Analysis). Up to that point I had been designing the bike by the seat of my pants based off what I thought a strong bike looked like. Learning and using FEA changed my life. I tested my links and my frame and I found that some aspects of my initial designs would have failed under hard bottom-out situations. My bike would have actually bent. Luckily using FEA I was able to come up with solutions that exceeded my requirements for strength and avoid these major headaches.

The last major hurdle was learning how to fabricate metal parts using a manual mill, lathe, and hand tools. Learning how to hit very precise tolerances over and over is very difficult, especially when the machines are cheaper Chinese ones! I generally try to hit a tolerance on critical parts of plus or minus 0.01mm. That's a full range of less than one one-thousandth of an inch. The equivalent of 5 times smaller than the thickness of an average human hair. I would say that I've definitely come the furthest with my fabrication skills. Something that is extremely valuable going forwards with developing the next version.


Bike Check Evan Turpen - Fabrication
Bike Check Evan Turpen - Fabrication
Bike Check Evan Turpen - Fabrication


What factors did you give high priority in your development? You mentioned you wanted the fastest bike possible for its intended use.


Everything. But the main focus was always on speed and control, so priority was given to the kinematics and geometry: axle path, leverage ratio, anti-rise and anti-squat had a heavy focus. Carrying speed, predictability and generating grip are all really high on the list. I'm particularly proud of the anti-squat I achieved with this design. To the best of my knowledge no rear derailleur driven high-pivot bike has achieved what this one does.


How, from all the available choices, did you narrow down to this suspension layout and design?


I like simple things and I like smart things and I really like simple and smart things. When exploring all the different ideas that I had this was the simplest layout that consistently achieved the highest number of goals I had set for the bike. To the untrained eye and even to the trained eye it looks like a simple linkage driven high single pivot. And that is technically correct, but what it achieves goes well beyond the preconceived notions for that style of bike.


Were there any avenues that you went down, only to find you needed to backtrack and find another?


For sure! The first design that I thought was the end-all be-all had extremely high pivot forces. It would have tried to rip itself to shreds. Multiple iterations leading up to the current design had issues too. I would get really far along in the design only to find some death-blow clearance or strength issue that I couldn't work around. So many disappointing failures, but you learn from each one and hopefully don't repeat them ever again.


Bike Check Evan Turpen - Fabrication
Bike Check Evan Turpen - Fabrication
Bike Check Evan Turpen - Fabrication





The Bike

What are some specific details on travel, geometry, suspension characteristics?


I designed the bike with two travel settings so that I could have two bikes to test in one. It has a 140mm setting and a 164mm setting that both use the appropriately sized shock for that travel. I am about 5 foot 9-1/2 inches tall (177cm) and the frame has a reach of 480mm which is just perfect for me. The seat tube angle is plenty steep for climbing too. At my saddle height the effective seat tube angle is 77.9 degrees. Head angle is set to 64 degrees and I am running an extra short 37mm fork offset (something that I had been testing on my prior bike). BB height is 341mm in the 140 and 350mm in the 164. Reach, stack, headtube and seat tube angle remain identical in both travel settings. Chain stay length is 435mm in the 140 and 432.4mm in the 164. Because of the rearward axle path both bikes sit around 445-448mm chain stays at sag.


Bike Check Evan Turpen - Leverage Ratio
Bike Check Evan Turpen - Anti-Rise
Bike Check Evan Turpen - Anti-Squat
Bike Check Evan Turpen Pedal Kickback


Kinematically the anti-squat is 100% at sag in every gear combination and is extremely stable even if you venture outside the sag zone. It pedals amazing. Anti-rise is 100% at sag. This bike is super stable under braking. Watch a Formula 1 car braking hard for a corner...It barely moves, it's just stable and planted and allows for the best control under braking. That's what this bike does. The axle path is also 100% rearward, but isn't so extreme that it creates awkward handling. This really helps the bike carry speed well through rough sections. The other benefit of the rearward axle path is increased front end grip from the bike naturally loading the front tire as you load the suspension into a corner. The bike really does create an "All Wheel Drive" feeling of traction and control for you. The leverage rate is also progressive and designed for increased small bump sensitivity and great bottom-out resistance. It is both coil shock and air shock compatible and you don't have to stuff air shocks completely full of volume spacers to get enough ramp up.


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Who built the frame?


I built the frame, but I hired John Caletti of Caletti Cycles to TIG weld it. He's a local high-end frame builder who specializes in titanium and steel frames. He is an absolute wizard with a welding torch and there's no way I would have trusted the frame if I had welded it. I also hired local machinist bad-ass Dave Mather of Mather Machining to CNC machine my links and idler pulleys. He did a tremendous job of nailing the tolerances I specified and I will definitely work with him again. I bought my headtube, dropouts, brake mount, cable guides and seat tube sleeve from Paragon Machine Works. All other parts you see on the frame were machined by me on a manual mill and lathe. And some parts were made with saws, files and a power sander with a careful eye.


Why steel for the first frame?


Because it looks bad-ass! And I grew up during the heyday of Brooklyn Machine Works. Well, actually this was a decision I made in the first few months of researching fabrication techniques. It also came down to the fact that Santa Cruz County has some really amazing custom frame builders that work in steel and titanium. Aluminum has a couple extra steps required as well. After welding an aluminum frame it has to be baked in an oven until it is in an "annealed" state. This makes the frame very soft so that you can properly align everything (bend it all back into shape) after the distortion from welding. After it is aligned, it has to be heat treated which is another trip to a special oven in order to bring it back up to its original strength. If you don't take these additional steps, then your frame will be much weaker and likely fail.

Generally welding 4130 chromoly steel doesn't require post welding heat treatment to be strong enough to ride. Also, my welder, John, did an amazing job keeping the frame straight and minimizing distortion from welding. This frame is straighter than most production welded bikes and my geometry and kinematics were maintained really well because of this. 4130 tubing is also stiffer than aluminum in a more compact package so it allowed me more clearance to work with while maintaining a great level of stiffness. Going forwards though, if done right, aluminum can save quite a bit of weight over steel and maintain a good level of stiffness if tubing size goes up.


What challenges did you find from going from a computer model to a physical bike?


Too many to list. The biggest challenge was jig design and figuring out the best way to accurately hold everything in place so the frame was actually what I designed when it was done. This is probably the most important step when making a frame. That and mitering the tubes to fit as tight and straight as possible.


Bike Check Evan Turpen - Bike

Bike Check Evan Turpen - Bike
Bike Check Evan Turpen - Bike


Did you need to go backwards and forwards between the computer and manufacturing a lot or did you know exactly how you wanted to make the bike while you were in development?


Sometimes. A lot of times when I would have an issue figuring out how to accurately make something I would improvise and create a one-off special tool just to perform one single task. If it allowed me to make the machines do the dirty work in making the part I was all for the increased time and effort it took.


When did you realize you could apply for a patent?


Pretty early on in designing the bike I realized the uniqueness of what I was able to achieve with anti-squat, anti-rise, and axle-path and I knew I needed to apply for a patent on the design. The anti-squat is the most unique feature of them all. To the best of my knowledge no current or past high pivot bike with a rear derailleur based drivetrain achieves 100% anti-squat at sag in every gear combination. With a gearbox and single final gear this is easy to accomplish.


How has the bike been received by your peers? What’s the feedback?


Well...so far, the only one to ride it properly has been me. First ride on it was one-week ago. I am really looking forward to getting as many people on the bike to offer their opinions, feedback and experiences with how it rides in the near future. I'm not afraid to see what other people think. And I'm really looking forward to pitting it against the clock through racing and back-to-back comparison testing. The clock doesn't lie!


Is the adjustability in the bike for a specific geometry or kinematic purpose or just for you to play around with things and learn?


The adjustability is simply there so I can test this suspension design in two major different categories without having to make two bikes. The shorter travel is more of an aggressive trail/all-mountain setup and the long travel is a full on big-hitting park/enduro bike. Both configurations weigh pretty much the same, so it's really only testing suspension performance and how that relates to the experience on the trail.


Bike Check Evan Turpen - Bike
Bike Check Evan Turpen - Bike
Bike Check Evan Turpen - Bike


There have been a few emerging high pivot bikes recently, what do you say this bike has over its competition?


Everything at the moment. Well, almost everything... it's not carbon fiber so it is heavy. I wanted to take the performance benefits of a high pivot bike and eliminate the negative traits I've experienced while riding them in the past. Kinematics were huge, but also drivetrain efficiency and noise. My idler is 22-teeth for better durability since the loads are distributed over a larger surface area and the angle change that each link has to make as it enters and exits the idler is less. It also utilizes a really nice bearing that can more than handle the loads that it sees without being damaged. With my idler location being so far forwards the angle that the chain sees at the extreme ends of the cassette is noticeably less too. This gives you less efficiency losses in your climbing gears where you spend the majority of your time. And also, better efficiency further down the cassette when you are going really fast! I'm excited to eventually perform scientific efficiency tests on this design compared to a "normal" drivetrain and post the results. Judging drivetrain efficiency by feel is great, but you can't argue with actual numbers.


The devil is in the details, as you say. Which is your favourite detail? Is there a story behind that particular one?


One little detail that I really like as a bike mechanic is the lack of spacers required for the BB and cranks. This bike uses Super-Boost Shimano XT 12-speed cranks paired with a DH 157mm rear hub. The cranks are designed to be installed on a 73mm shell frame with 3 different spacers in various locations. I utilized all the space that would have been taken up by spacers to widen my BB shell as much as possible for an even wider and stiffer BB pivot and widest stance possible for the BB bearings. This also made it so there were no spacers to mess around with when installing the cranks. It's nice being able to do whatever I wanted since this was a one-off bike made just for me.





The Next Bike

You’ve mentioned you’ve learrned a lot from getting to this bike. What were the biggest things that you’ll take into the next bike?


So many things! Namely jig design to improve weldability, lowering the forces acting on the frame so it can be made lighter and stronger, and designing the bike smarter to make it easier, and less expensive to fabricate. Stuff doesn't have to cost more to be better. Smart design can make products less expensive, lighter, and stronger.


Have you now invested more into the next bike with the move to an aluminum construction?


I haven't invested anything yet. I don't have any money to invest! I'm actually going to fully run out of funds by August of this year. The goal is to plan out the next steps and secure enough funding to keep moving forwards. If I have to go back to working as a bike mechanic full-time my progress on this bike will slow drastically.


Bike Check Evan Turpen - Bike


Is this looking like a venture to selling the bikes at some point?


100%. Yes. The plan is to start small with a batch of at least 25 to 50 high-quality frames and then go forwards from there. They will be aluminum versions to save weight and be built entirely here in the U.S. Doing so helps ensure the best quality product, a timely development cycle, and a very enjoyable experience for those that choose to buy one of my future bikes. Carbon is something that I would like to do eventually too, but just doesn't make sense right now with such small initial numbers.


When are you planning to have version two?


The goal is to push hard to have version two ready to ride sometime in the fall of this year using everything that I've learned from this bike and more. It will also be my first foray into building an aluminum frame that will be much more representative of a production bike.



A big thank you to Evan for all the information and sharing his bike with us







147 Comments

  • 136 2
 Just gonna put this out there: I'd buy one.
  • 55 21
 This bike is so SICK i just got COVID !!!
  • 3 1
 Ditto.
  • 2 0
 @filmdrew: to soon? :-))
  • 12 0
 Doesn’t look like a trek session
  • 3 0
 What's the weight at this stage, cause I might be wrong but it looks like it's gotta be 35lb +
  • 11 2
 @landscapeben: less than an average Commencal
  • 2 0
 @pdxkid: I'd be surprised if that were true.
  • 6 0
 @landscapeben: 39 lbs complete, 12.5 lb frame including shock.
  • 1 0
 @EvanTurpen: wow that's a big boy!
  • 1 1
 @EvanTurpen: who cares if it's heavy, it'll just be faster on the downhills, and that's all anyone cares about (right?)
  • 1 0
 @EvanTurpen: yo what's the status?
  • 2 0
 @englertracing: Still working on the design of the next version...It's getting close...The hardest part has been packaging it all into a small frame version. It's so much easier to make things fit on the larger frame sizes. I want to make sure that I have a bike for almost every height of rider and not just tall folks.
  • 1 0
 @EvanTurpen: I can't wait to see it!
  • 49 1
 That’s awesome. I was reading and I scrolled down and seeen the “weight” was 180lbs haha I was like holy shit what a tank
Took me a while to realize I was looking at the riders weight not the bikes weight
  • 7 35
flag vjunior21 (Jun 23, 2020 at 12:28) (Below Threshold)
 You thought is was an E-Bike at 180 lbs so it made sense. Then you saw the pictures, realized that it did not have a motor and that the 180 was the rider weight. LOL
  • 30 3
 Speaking of rider attributes, I chuckled at "I am about 5 foot 9-1/2 inches tall". Definitely an engineer perspective!
  • 1 0
 did the same.
  • 20 1
 @deadflat: Everyone under 5'10" adds the extra 1/2" if it's there. (Source: I'm 5'8-1/2" tall)
  • 3 7
flag takeiteasyridehard (Jun 23, 2020 at 19:53) (Below Threshold)
 @kazomado: usually not women...
  • 6 0
 @kazomado: If you measure your height first thing in the morning it will be about 1/2" more than just before you go to bed as your semisoft tissue such as cartilage compresses throughout the day and decompress at night. I saw this in the old movie 'The Incredible Shrinking Man' and thought 'pffft', but I found it to be true.
  • 12 1
 @deadflat: The Metric system does exist.....1765.3mm...There you go
  • 1 0
 @iamamodel: As physiotherapist it's the intervertebral disks that got compressed by the weight.
  • 1 0
 @kazomado: me? I'm 5 10 3/4. Didn't make 6, see?
  • 37 1
 +1000 for the squish video
  • 5 2
 Agreed!!!
  • 32 0
 I am so unbelievably stoked to see this bike come to life!! Seeing it come together over the last 2 years has been incredible and I am so happy for you Evan!!
  • 8 0
 Very cool, congrats! hope to see y'all (and this) in the woods.
  • 32 1
 Fukcing rad, I would be over the moon if I created that.
  • 47 0
 I'm sure it's great for jumping, but i think you're a bit optimistic.
  • 10 0
 No doubt! Sometimes I get my toast wrong and cook the bread with the jam on it.
It’s a marvel I’m wearing pants today actually.
  • 3 0
 @dinklecorn: hey, if the cow can do it.
  • 1 0
 @Waldon83: At least your underwear is on the outside right?
  • 1 0
 You have to wear underwear with the pants?
Man have I got a lot wrong in life
  • 25 1
 I was fortunate to meet Evan a few weeks ago, see his bike and learn about this awesome project. He complemented my fresh Ripmo build. When I asked what he was riding, he “said, my bike”. “Yeah, what kind?”. “My bike, I built it”.

I was aware of the benefits of high pivots and their design challenges, and was extremely impressed with everything I saw and heard. Evan allowed me to pedal this bike up hill, twice, sprinting very hard the second time all the way down the cassette. I’ve never felt anything like it. A hardtail comes closest, and I described it to Evan that way. To be clear I was referring to its pedaling efficiency. It obviously had superior traction, but that rear suspension didn’t react to my sprint at all, yet the rear wheel tracked the ground. Hence the benefits of the high pivot. The nearly flat 100% anti-sag shown in the article across the gear range and sag suggests the suspension won’t strongly react to pedaling forces, and that’s exactly what I felt. Similarly, the rear didn’t rise under braking, feeling again like a hardtail, but with tons of rear wheel traction. I repeated the same tests with my Ripmo, and despite being around 9lbs lighter, it felt much slower uphill because so much of my power was being dissipated in the rear suspension, especially down in the 10t.

It’s awesome to see this article, and the well deserved buzz. Best of luck to Evan and this project.
  • 24 0
 Absolutely beautiful work and putting most brands to shame. That pedal kick with that antisquat is hard to get on a high pivot
  • 22 1
 Art. Pure art...
  • 14 0
 Hey, Evan where is your "Go fund me page". I would send you a few bucks. It looks like the bike you have build might be just different enough to make people curious about how it will ride. I'm curious.
  • 13 0
 No Go Fund Me page...not really a believer of putting the investment responsibility on my potential customers. I plan to fully develop the bike first and once it is all ready to go, make it available. I don't want a "Sick" situation...
  • 4 0
 @EvanTurpen: Much respect for your approach. Also, I am a big fan of your desire to go with steel and would probably support the idea of staying with it if you can source a lighter weight gauge steel (SuperTherm).

On the flip side, I have worked with a handful of companies with R&D and have seen good bikes/products not make it to market or succeed after getting to market because the designer/builder believed they could handle everything on their own, in house. I would be happy to talk stories with you and provide some insight based on my years of experience in this industry if you want to message me directly... Otherwise, good on ya.
  • 14 1
 Has your patent application published yet? As a patent attorney/cyclist, PB's drops of bicycle related patents are definitely among the high points of my online activity. Good luck with the frame building venture.
  • 4 0
 Not yet...the provisional patent has already been submitted and I still have a little more time to submit the final "non-provisonal" patent which will claim the priority date of the provisional application.
  • 3 1
 @EvanTurpen: Cool. Make sure that non-provisional app gets filed, lest someone at Cotic or Production Privee get "over-inspired". Smile
  • 11 0
 Bike looks rad! Hopefully the production model will be out soon. Great work Evan.
  • 13 0
 Great work ET
  • 3 0
 Thanks Logan!
  • 11 0
 Very cool bike! Way to dive in big time and chase your dream Evan!
  • 11 0
 Just awesome. Some refreshing reading too.
  • 7 0
 Wow. That is just amazing. As a taller person for whom there are very few full suspension bikes to really choose from beyond Geometron (and no high pivot idler bikes that I know of) I'm on the lookout for a design that's doable as custom, which a steel bike definitely is. Evan - DM me!
  • 7 0
 How many chainlinks are on this thing? I counted about 144.
I like that the chainwrap is decent on the idler and chainring, more so than the Supreme DH's idler.
Absolutely digging this bike, needs an awesome name to go with it!
Sign me up if you are expanding operations.
  • 4 0
 If I remember correctly it took one full length Shimano XT 12-speed chain which is 126 links + a 10 link section (including the extra master link). So 136 links. Hopefully Shimano and SRAM will sell bulk continuous rolls of chains to me in the future so that I can have only one master link on production bikes.
  • 6 0
 As an engineer... no I'm kidding, but as someone who's spent a bit too much time doing high pivot bikes on Linkage and in 3D, I'm a fan.
Several times I moved the pivot forward like this, and I also tried to get the shock activated from behind, and I also wondered about having another "tube" angled like this in front of the seat tube, but I never thought about mixing all of it and refining it until it's perfect.

And there's enough space for a water bottle Wink
My only reserve would be the exposition to dirt. And maybe leg exposition to the chain.
  • 6 0
 This bike is awesome. I also am about your size, live fairly close, and would be interested in testing it and maybe even buying one down the road. So if you're serious about people riding it.... please let me know. I'd even pay for the privilege.
  • 7 0
 I've seen a lot of bikes on this site by people doing hodge podge, diy suspension with steel bikes. THIS BIKE IS BY FAR the most well thought out design I've seen. It's very, very cool. Super rad job Evan and John!!!
  • 10 1
 This is so sick... AND he has dominions!
  • 8 0
 Masterful execution through the learning curve. Full credit Evan, great job!
  • 5 0
 Oh my gosh even as an engineer I hate using Creo! Sorry you had to suffer through that.

For version 2 I'd recommend looking into something a bit friendlier like Fusion 360 or onshape or even IronCAD.

Also while less user friendly than the above 2, but easier than Creo is SolidEdge. It has good support for designing frames and a free student license is available (though not sure if it includes the frame design module in the free version.)
  • 3 0
 Thanks for the hot tips! I may try Fusion 360 since a license is WAY cheaper...
  • 1 0
 Agreed, I've been using Creo for the last three years, and its still immensely frustrating at times! I used solid edge for a year before that, and found it very opaque to learn, but mostly pretty good to use after the initial learning curve
  • 6 1
 Dude, Evan, your bike looks incredible! Forget the coolness of the steel tubing, just the concept of the high single pivot alone, along with that well thought out linkage, is so good! Congrats on making your vision a reality! Hope to see you find a way to produce more of these soon- and in whatever material you determine is best! I'm not a steel hater, I just don't want to have blinders to the fact that the design of this bike is extra special-not just the material! Well done!
  • 8 2
 Fantastic job Evan!!! Such a pleasure to read your interview.
I hope we`ll hear from you soon, in a near future Wink
  • 5 1
 Way to go Evan! So awesome to see someone actually take an idea and make something tangible out of it. I'm sure the bike rides great too.
  • 5 0
 That is some seriously good fabrication work.
Kudos to all involved; that's a piece to be proud of!
  • 6 0
 Hell yeah ET this turned out sooo rad!! Friggin' props
  • 2 0
 I too grew up in the era where nothing was radder than a Brooklyn. I've always had the mission that someday I'm gonna learn to build my own bikes and build a modern BMW link bike. This guy did it (I was just gonna change the angles and BB height, he went all out).

Crazy that 15-20 years ago a BMW frame + cranks was $3600 and it was exorbitant. Be a bargain these days.
  • 2 0
 Damn, Evan. I remember riding with you to Northstar about 13 years ago and you being all excited about designing a bike in linkage and asking Bill about the patent process. Really cool you followed through. Not only designing a super rad bike, bike quitting your job and taking out a loan takes some serious grit. Well done. BTW, check out Fusion 360. Not sure about their FEA, but Creo and Solid Works are pretty cost prohibitive for a startup.
  • 2 0
 Brilliant job on geometry and layout, Evan! How is rear axle torsional stiffness on off-camber sections? Does the rear axle/wheel twist relative to the bike's centerline with the steel rear?

I notice that you're in Aptos. If you don't know Dave Smith, Structure Cycleworks' rep in CA, drop him a line at dave@structure.bike. You are definitely two guys who ought to swap bikes for a day!
  • 7 1
 SO SICK !
  • 6 0
 Well done indeed!
  • 5 0
 Great job Evan!!! This is a dream bike!
  • 3 0
 This bike looks amaaaaaaazing! You are my hero for providing a suspension squish video. Everything looks really well thought out.
  • 5 0
 Be steel my beating heart.
  • 1 0
 Probably been covered already but "I didn't have the resources or access to CAD" is no longer a valid excuse for not working on a project or designing something like a professional engineer would. AutoDesk fully supports DIYers and small businesses by providing access to Fusion360 for FREE which includes CAD, CAM, FEA plus a forum and tons of YouTube videos to educate yourself.

Anyway awesome story and really cool bike. Well done Evan!
  • 1 0
 I have a feeling there there is more advanced kinematics beyond the usual anti-squat/anti-rise standard limited knowledge mantra. I see the front chainwheel being the MAJOR hurdle to mainstream acceptance for many reasons, like what if someone wants a 28 or 30t chainring? Weight, increased complexity and cost for the linkage and frame. Simplicity is always important on so many levels.
  • 5 1
 This is a better donut!!!
  • 4 0
 Unreal! Amazing job, nicely done.
  • 3 0
 That’s an awesome looking bike for a prototype! Looking forward to seeing the production version ????????
  • 2 0
 Interesting how bearing at bb link will be rotating round bb axel & moving with the link, will that cause bearing kick back?
  • 4 0
 The bottom bracket/pivot axle does not rotate with the lower link. It stays static in relation to the front triangle. The lower link rotates around the static bottom bracket pivot axle on a pair of 40mm inner diameter MAX type bearings. The only kickback is the regular chain induced kind shown in the charts. It is fairly low compared to a traditional non-high-pivot bike.
  • 1 0
 @EvanTurpen: Good to know! Does look good !
  • 1 0
 That name brings back good memories, i dont know how often i watched the old DH racing videos back then, and i remember his name popping up quite a lot of times. Glad hes doing well.
  • 2 0
 Beautiful build Evan! Being a welder and cyclist I’ve always wanted to go this route. I can’t wait to see this go into production!
  • 3 0
 Very nice. Maybe Nicolai can help with the alu thing?
  • 2 0
 And hopefully gearbox?
  • 2 0
 How's that rear tire clearance in mud because it looks really tight to that lower link.
  • 2 0
 I haven't ridden it in mud yet since it is summer in California and the bike is currently raw unpainted steel. If you watch the suspension squish video you can see that when you are sagged in the clearance on the link increases dramatically. This allows it to clear debris quite well.
  • 3 0
 BROOKLYN MACHINE WORKS FOREVAAA
  • 3 0
 fuckin A! can't believe u just ent n did that
  • 3 0
 I’ll take one in titanium
  • 2 0
 WOW ... those pedals do not even move when going through the suspension stroke!
  • 1 0
 Very cool! Always like to see small builders still out there! Also kind of laughed at the NWUs being used as welding apparel.
  • 1 2
 I'm not interested in buying one (I already have a great bike I don't intend to replace anytime soon). But I would definitely be interested in testing it out and giving feedback. I do really big days on an already heavy bike, would be interesting to compare how it performs.
  • 1 0
 “ I had no idea what I was getting into, but the concept of blind racing in epic locations was rad.”

Wish the UCI thought like this...
  • 2 0
 So cool. Thank you @evanturpen for following your hunch and making this real.
  • 2 0
 Thanks CHAR!!!
  • 1 0
 Please keep us posted as to the availability of this frame. I am in the SF Bay Area & will be in the market for a new alum bike next spring.
  • 1 0
 For sure! I will eventually have a website where you will be able to signup to a newsletter if you want to be kept up to date on progress and eventual availability on production bikes.
  • 3 0
 Increible
  • 3 0
 hell yeah!!!!
  • 3 0
 Neato!
  • 2 0
 You had me at externally routed rear brake hose!
  • 5 0
 As a mechanic I am a big fan of external cables. They may not look as fancy as internal cables, but they don't rattle and when your brake inevitably has some issue you can simply put a new one on without even having to bleed it.
  • 3 0
 Stunning.
  • 2 0
 Wow, what a cool bike, Love it!
  • 2 0
 Thanks for the shout out Evan! Funnest machine shop project ever!
  • 1 0
 Hell yeah Evan!! So stoked to finally see this off of the computer screen!!! This is amazing
  • 1 0
 Wow congrats Evan. My bike will miss your expertise at SVCS but we are both very happy you are following your passionSmile
  • 1 0
 The sight of a unique rig like this one scratches an itch I didn't even know I had. Magical!
  • 1 0
 Love the bike Evan.. I would deffo buy one, if that ever goes into production!
  • 2 0
 someone fund this man so I can buy this bike!
  • 2 0
 I would buy one if it comes available to public
  • 2 3
 If you love custom high pivots check out what Daren is making.
I had him make me one in 2015 and it is sick.
www.facebook.com/wraithbicycles
  • 3 1
 Looks like a Brooklyn.
  • 1 0
 Exactly my thought - and a Balfa.
  • 2 0
 So dope Evan!!!
  • 1 0
 Standing by for 3rd party review!
  • 1 0
 "..Why steel for the first frame?
Because it looks bad-ass! "

What ??
  • 1 0
 this is badass bike; BB just super rad looking
  • 1 0
 Bushings in the suspension pivots? Great looking bike...
  • 3 0
 No bushings in the pivots...It has double, double-row MAX-type sealed cartridge bearings in the main pivot and upper link to swingarm pivot on each side. The lower link has 2 massive MAX type bearings that are concentric to the BB and the lower link to upper link pivot only needed one double-row MAX-type bearing per side as the forces were lower here. The rear shock currently has the stock Fox IGUS bushings instead of the needle roller bearing setup because they hardly see any rotation and the bushings can take higher loads without getting damaged. The back end is incredibly smooth when cycling it without the shock installed and is super smooth off the top when the shock is installed too.
  • 1 0
 What an amazing bike! Congratulations. I would buy one for sure
  • 1 0
 @gnarnaimo: Dude. Just wait until you hit 65.....
  • 1 0
 That suspension linkage
  • 2 4
 I would be afraid of getting my ???? ⚽️’s caught in that upper sprocket.. Don’t want any more teeth down there between my legs than necessary
  • 8 0
 Damn dude. I would never normally say this, but you might want to consider some plastic surgery if they hang down that low. Also, avoid wearing shorts around schools maybe.
  • 1 0
 @gnarnaimo: Thank you for the advice.. It’s a serious problem for me.
  • 1 0
 Nice bike
  • 1 0
 Very nice.
  • 1 0
 Trust in rust ????
  • 3 0
 It's currently raw but lightly oiling it every once in a while is keeping the rust away until I get it painted.
  • 7 9
 Awesome! But why spoil it and make it from aluminum? Kinda takes the magic away. Not enough steel bikes on he market.
  • 16 1
 Great thing about PB articles are that there's always some who doesn't read it.
  • 3 0
 Cause not everyone wants a super heavy bike.
  • 2 0
 Because probably the number one complaint on PB is "too heavy" when it comes to EVERY bike.

(I ride a 40 pound bike, so, not me)
  • 3 0
 It really comes down to weight and stiffness. If somebody wants a 12+ pound frame to pedal all day maybe I'd consider making some. I love the look and feel of steel, but it's hard to make light when you start adding linkages, burly bearings, and an idler. There's a reason why most of those steel full suspension frames out there are fairly simple single pivots.
  • 1 0
 @EvanTurpen: how much difference are we talking? How heavy is this beast anyhow? stanton makes a half and half bike. Steel triangle and aluminum rear triangle. That must be there reasoning too. I’ve never been one to care too much about bike weight.
  • 1 0
 @Ajorda: I read it that’s how I know the production version will be aluminum. I know the reason is weight but some propensity really don’t care much about that.
  • 1 3
 This bike flex has to be next level. I like the whole process but doubt about driving characteristics
  • 2 0
 It's actually quite stiff. The lower concentric bb link and the upper link connect to the swingarm just in front of the rear tire. This adds a tremendous amount of support to help negate torsional flex from the long overall swingarm length. For comparison...my friend owns a Firebird 29 with the Super-Boost 157 back end. This bike is considered to have a very nice level of stiffness out of the back-end. Not overly stiff, just nice. He is over 200 lbs and he rode my bike, did the "standard" non-scientific "pushing on the cranks from the side with your foot "and the "wiggle the back wheel with your hand" test, back to back between his Pivot and my bike and he said they felt practically the same. In the time that I have been riding it, I haven't had anything stiffness-wise with the frame to complain about. The next version should have many improvements to make the bike even a little stiffer and lighter at the same time.
  • 2 4
 Gotta buy two chains
  • 15 0
 @Ajorda: Two wheels too. Coulda bought a unicycle and saved big. Eh?
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