When Gerard Vroomen and Andy Kessler launched Open Cycles back in 2012, they wanted to push the limits of lightweight and stiffness on mountain bikes. And their original Open 1.0 did a pretty good job of kicking things off. Then they released a special edition AXX1 model and others that brought the complete bike weights lower thanks to a very, very expensive builds.

Now, they’ve gone back to the frame to eek out a bit more performance and shed a few more grams. The new Open One will be made in Germany using a new layup process and unusual frame details. The result is a frame that comes in as light as 796g for a Large…


One of the biggest visual changes is the dropped drive side chainstay. This layout let them improve clearance for the chainrings and tire without having to use an overly tall tube shape. They say it provides all the stiffness they want with minimal material. From there, the chainstays flatten slightly to work with the bowed seatstays to improve vertical compliance.


The seat tube was slimmed down a little, then vertical ribs were added to the sides to prevent lateral flex and reduce the likelihood of buckling. The slimmer size better fits the slightly narrower PFBB30 bottom bracket. Before, they used BBright since it provided an ultra wide and very stiff platform. Thanks to an extended BB shell that creates a thick bridge going back to the chainstays, they maintained stiffness while making a frame that’ll work with many more cranksets.

Out back, they switched to a very slick thru axle. The threaded end doubles as the mount for the rear derailleur hanger, keeping the overall weight the same as with QR but much stiffer.


Part of the reason for moving production to Germany was access to premium pre-preg fibers. They wrapped hi-mod UD fibers from the top and down tubes around the head tube. The woven fibers are a lower mod (but not lower quality) with what they say are very high end resins. These provide the necessary strength while the high mod stuff improves stiffness.


All in all it’s a very good looking frame. Production weights are simply claimed as “under 850 grams”, which pushes the boundaries of light weight for mountain bikes. Some of what you’re seeing here can also be considered a teaser for a (near) future full suspension bike. Droooooool.


  1. So, in order to save 50g they had to absolutely ruin the rear cable routing to the point that it has an outrageous kink in the housing? No doubt we’re talking about triathletes here….

  2. Let’s be honest, we’d all be happy enough to ride one…but I’m not buying the “upend traditional hard-tail design” idea 🙂 Giant XTC hardtails have just as much going on with their own factory-made carbon and it is good enough for a lifetime frame warranty. (Yes, I’m clearly a proud owner).

    Show me your warranty terms, Open, then we’ll talk.

  3. Looking at the first open bike it was pretty clear it was a mtb designed by people that think a flat fire road is mountain biking. This one is even worse… That kink that will make the most expensive drivetrain money can buy shift worse than alivo is bad enough, but it’s one of their glamor shots, meaning they don’t even know enough about bike mechanics to know that it’s wrong.

    I’d consider $6-700 a fair price for this frame, but I bet it’s the most expensive hardtail frame you can buy at over $3000.

  4. As an owner of the first Open I can assure you that these frames are made for use on all rough and rocky mtb trails. I have absolutely punished mine in Australia for the past 12 months with lots of large drop offs, jumps and rock gardens with no issues what so ever. In answer to Michael’s question regarding warranty, Open offer 10 years on the frame.
    My Open is by far the lightest bike I have ever owned and the most responsive, looking forward to checking this one out and the Dual Sus when it is launched.

  5. did they put enuf clearance for anything bigger than a 1.9 in there yet ?? modernize the geometry from 2002 this time around ?? mtn bike from a tri-guy. ahem.

  6. Leave it to Cervélo (founder) to again puch the boundries of bike tech, this time in mtb! For those that don’t understand carbon frame tech or know the history of carbon road bikes need to open the history books.

  7. Who cares about that kink you weirdos, that is not a show stopper. This is an awesome feat to make a got d*mn 800g mountain bike frame. i love the look with the AX parts too.

  8. Actually while building this bike, I was thinking the same. The cable bend is pretty extreme, but I can report that shifting was not compromised at all.Nevertheless this frame begs for Di2. For anyone that has put a leg over an Open Cycle, knows,these bikes are for the most discerning of riders. The feeling of riding an Open,let alone the One,is unlike any hardtail composite 29er I have ridden. Pure point and shoot acceleration all while never asking for more compliance.Once again Gerard has perpetrated his spirit into production of another discipline.

  9. The kink is a showstopper. It makes a multi-K drivetrain work worse than Alivio (which I would argue, works OK). Give us external routing, please.

  10. Guys, please stop completely misusing the word “showstopper” – it’s definition is pretty much the opposite of what you mean. I believe “deal-breaker” is the phrase you’re looking for.

  11. Mark here with Pro Bike Supply. We put this bike together and although there are a few details that need some tweaking, overall this is a very impressive frame especially considering that this is the very first frame off the production line. I agree that the rear cable routing does need a little work and Open is considering alternative options.

    What really blows me away about every frame that Open Cycle produces is the stiffness, compliance and exceptionally low weight. There is no other frame on the market that comes close the lateral stiffness of an Open while at the same time being comfortable to ride even after 6 hours in the saddle. Factor in that they also make some of the lightest hardtail frames on the market and you then get a real understanding as to why this frame is a showstopper.

    Hardtails are not for everyone but if you are considering buying one then this frame should be at the top of your drool list.

  12. I’d like to see a comparison of stiffness (lateral/vertical) to other more popular brands (S-Works SJ, C’dale Flash 29, Trek Superfly, etc). Looking at those chainstays and I’m thinking this rear end feels like a wet noodle.

  13. Pretty sure Specialized tried this routing when they redesigned the Roubaix a few years ago. Our shop got three of them in and we couldn’t get the shifting to work properly.

  14. This frame is the part. It would win any test compared to spesh, trek, cannondale and all that (deleted). Specially if you consider weight stiffness ratio. This is no asian crap, this is made by the German guys who are asked to do parts for quite a few formula one teams for a few years now. Those don’t work with asian (deleted).

    That been said, at 4200€ (about 6000$), well…

  15. Guys, a frame can only get but so stiff before it becomes a moot point. $6000 frame from Cervelo? That’s a joke, and it’s not even funny. Also, when you’re trying to compete in this kind of market, thinks like super janky cable routing do matter. You pretty much lose all credibility if you can’t get something as simple as that right.

  16. I wouldn’t call this cable routing “super janky” – probably not ideal, but as Marc said, it seems like it doesn’t compromise shifting that much. And yet the comments about “this thing MUST shift like crap” keep on flowing…I’m willing to bet half the people criticizing don’t get the weird perspective going on in the photo. The housing loop is tight, but not pinched – it bends out quite a bit. And if you can’t get this to shift smoothly (even WITH alivio) then you clearly don’t know how to treat housing ends properly after cutting them.

  17. An old school avid roll-a-ma-jig would be a quick solution for that rear cable problem. I don’t know about putting one on a 4800 frame. It seems for that kind of money cervelo could engineer a better solution.

  18. First, It’s not a Cervelo. Secondly, I own an Open O 1.0 and can attest to the stiffness. I greatly preferred the rear braking performance of the Open over the Sworks stumpjumper. In full disclosure I also have a 29″ Epic (2014 carbon expert) and a 26″ epic (2012 sworks) and wanted to like the Spec product, just hated the rear brake chatter (XTR on demo). Additionally, I feel the Open has better stiffness when applying power and better handling. The low speed, climbing handling of the Open is exceptional and my favorite aspect of this bike. I have raced it since December 2013 (short track and one 100K race) and have been very pleased with the bike as well as the quality of customer service. As mentioned previously, I am the anti-bike rumor and own 2 specialized bikes and love them both. If I have an issue with my specialized there is a substantially longer paper trail and time delay in getting it addressed, it is still addressed and addressed well, some of what I like about specialized. With Open, I email Andy and he responds; rapidly. I’m not a UCI pro racer but it’s nice to be treated as one when you spend the money for a product such as this.

  19. Thanks to those with constructive feedback. Regarding the kink in the cable, we definitely wouldn’t sell it like that. This exit position is perfect for something that wasn’t available quite yet at SeaOtter. For the standard set-up including XX1 which this frame in the end was built up with, it will have different routing.

    As for those predicting lack of stiffness, shattering carbon in crashes, etc, sounds like the same things the same people were predicting with the O-1.0 and of course none of that ever occurred.

    @TmonT Most run 2.1″ or 2.2″, some 2.25″ on their OPENs, so you must have been confused about something.

    And to clarify the pricing, it is $4800 plus tax, the $6000 misunderstanding probably came from somebody converting the Euro price but that includes Euro sales tax. Not that $4800 isn’t high, it is.

What do you think?