The OPEN U.P. frame

Unbeaten Path



Velo Atelier are very proud to be one of only a handful of retailers in Europe working with OPEN. Andy and Gerard's philosophy of only offering their frames through retailers that are knowledgeable and able to properly size, fit and build each customers dream bike to the highest specification, is truly refreshing.


U.P. (Unbeaten Path) and U.P.P.E.R. (lightweight version) combines a performance-oriented cross/road geometry & parts with clearance for mountain bike tyres. So you can ride anywhere, and ride fast.


Get out of town on asphalt, hit the gravel roads or switch to singletrack. The geometry gets you there fast; the big tyres make you unstoppable.

The frame is available in two versions:


-  The standard U.P. with 3T Luteus II fork for post-mount disc brakes

-  The superlight U.P.P.E.R. with OPEN U-turn fork for flat-mount disc brakes


Overall, the U.P. and U.P.P.E.R. share the same principles of intended use, same tire clearance, same exact shape and geometry. But they differ in layup, weight, fork, disc brake mounts, thru-axles and colour.

Tyre clearance

The U.P. fits mountain bike tyres up to 2.1” wide. But you can also fit a 40mm cross tyre, or a 28mm road tyre, or anything else in-between (exact tyre sizes depend on manufacturing tolerances and rim width, so this is a guideline. Always make sure you have 6mm clearance between tyre and frame).


How do we fit such a wide range of tyres without affecting the handling? Let's start with the numbers; below is the outside radius for various wheel+tyre combos:


Radius Rim Tyre

341mm 700c/29er 28mm road

344mm 700c/29er 32mm cross

350mm 700c/29er 40mm cross

342mm 650b/27.5" 2.1" mtb

365mm 700c/29er 2.1" mtb

As you can see, the top-4 wheel+tiye combos (700c cross/road tyres and 650b mountain bike tyre) are very close in radius, the bottom one (the 29er mountain bike tyre) is way off.

So you’ll hardly notice a difference in geometry swapping 700c cross/road and 650b mountain bike tyres on the U.P., while 29er tyres would make a total mess of the handling.


There is a second reason we designed for 650b and not 29er tyres. They would require very long chainstays, while the U.P. now sports a very short 420mm rear end. Most gravel and cross bikes have longer chainstays than that yet they can't fit anywhere near the same size of tyre.

Crank clearance

Behind the bottom bracket, the chainrings, frame and tyre all fight for space. And with the need to fit big mountain bike tyres and narrow Q-factor cross/road cranks & chainrings, the U.P. presents the toughest possible packaging problem.


Dropping the right chainstay moves it out of this crowded area, allowing it to be wider and therefore stiffer (a huge effect; with the same amount of material, twice the width will give you eight times the stiffness!).


TRCinTRS™ technology

“100% hi-modulus carbon”, “aero-space grade”, etc. Useless – and hopefully false (we’ll get to that) – claims meant to impress you.


It’s not about high- or low-modulus, it’s about the right carbon in the right spot. And because the bike industry loves techie-sounding abbreviations, we’ll humor them and call it TRCinTRS™.


Fact: stiffer carbon is more brittle. Strategically placed ultra-high-modulus carbon is a good idea. Making the whole headtube out of it when you have big impact loads is not!

The best lay-up is not 100% of one modulus; it’s a blend. We use the highest modulus (stiffest) carbon of any bike manufacturer where we can, and tougher grades of carbon where we must. That’s how our frames are both light and durable.


The rear triangle has to provide lateral stiffness for an efficient drive train, but vertical compliance for better comfort. The U.P. features chainstays and seatstays that are extremely thin vertically to provide that compliance, while their lateral width and layup ensure rock-solid propulsion. Truly the best of both worlds.



Flat-out downtube

The downtube is the key for stiffness, connecting the steering center of your frame with the drivetrain. The flat-out downtube’s characteristically flat outside faces allow us to strategically place strips of ultra-high modulus carbon far away from the center plane. The stiffest carbon exactly where it matters, guaranteed!

Zero-setback seattube

With a minimalist 27.2mm diameter we maximize the flex in our seatpost & seattube. This is especially a big plus on rough terrain. The seattube angle is designed around the use of a straight, zero-setback seatpost rather than a regular seatpost with setback (we’ve never understood those). Zero-setback posts are lighter, saving you another 10-30 grams (every little bit helps and you can then put that saved weight into a 500g saddle like the Brooks!).


Fully-internal cables/hoses

External cables & hoses collect dirt, risk getting stuck behind objects (particularly expensive with electronic shifting) and frankly, they are ugly. So the U.P. runs them internally.


With our proven MultiStop design, you can customize the frame for 2x10/11, 1x10/11 and Di2 shifting. Just pick the right insert. In case you run a single chainring, you can also remove the front derailleur hanger to further clean up the frame.

ThruThread dropouts

Most thru-axle frames are heavier than quick-release frames. Extra carbon for the dropouts, heavy hangers, and the axle itself. But they are stiffer, So what do you want most? The answer for most people is “both”, and so we introduce the first frames that combine a thru-axle with a lower weight. How?


The ThruThread design uses the same threads that hold the thru-axle to lock the derailleur hanger into the frame. Simple, light, effective.


We didn’t just redesign the dropout, the entyre seatstay and chainstay design is optimized with the added stiffness of the thru-axle in mind. For the thru-axle itself, we recommend the stiffest design available, the Syntace X-12, but you are free to use a different 12mm thru-axle if you  want

Toptube bag mount

For handy storage of your phone, camera, some tools or food, you can use the toptube bag mounts. It fits the standard toptube bags from for example Dark Speed Works and XLab as well as dedicated ruggedized bags from for example Revelate Designs.

SafePost™ Pilot hole

Seatposts usually indicate a minimum insertion dimension. That keeps the seatPOST safe, but it’s also important that the seatTUBE is supported properly. The minimum insertion for that is indicated by the SafePost Pilot hole.



Bottom bracket

The U.P. uses the 386 EVO bottom bracket standard. The wide (86mm) BB shell is perfect to attach the dropped drive-side chainstay to. Furthermore, it fits most of the cranks on the market, from Shimano, Campagnolo and SRAM (the GXP versions) but also smaller brands like THM, Rotor and RaceFace. 386 EVO even allows for the installation of many mountain bike cranks.

Disc brake mounts

One of the key differences between the U.P. and U.P.P.E.R. is the disc mount standard. The U.P. uses post-mount, whereas the U.P.P.E.R. is designed for flat-mount. We don't like how the bike industry keeps “inventing” new standards, so we always investigate if they are an improvement before we use them.


Post-mount brake calipers work very well, and the main argument for flat-mount is that it looks better (sigh) while a significant drawback is that the front brake always requires an adapter for mounting, adding weight and reducing braking efficiency.

So why did we decide to offer the U.P.P.E.R. with flatmounts? Three reasons:

1.  Shimano has decided to make the new DuraAce group only available for flat-mount. So to use their top group, you need a flat-mount frame or an adapter to fit post-mount brakes on a flat-mount frame.

2.  SRAM does offer all its brakes in flat-mount and post-mount versions, but the flat-mount calipers are lighter.

3.  We designed the U-turn, a new fork that accepts flat-mount calipers without the In conclusion, to use the lightest possible brakes from both Shimano and SRAM, you need their flat-mount brakes. And thanks to the U-turn fork, you can make those set-ups even lighter by removing the normally required adapter. A win-win.


The disadvantage is that you cannot spec the U.P.P.E.R. with post-mount brakes, so for example the exotic combination of using XTR mountain bike brakes on the U.P. is not possible on the U.P.P.E.R.


One more way we have squeezed some weight out of the U.P.P.E.R.: while the new U-turn fork is set up for 160mm rotors up-front, the frame will accept 140mm rotors in the rear. Since it’s the front disc that is the limiting factor in braking, this combination of bigger up-front and smaller in the rear makes a lot of sense and saves 10-20 grams depending on the brand of rotor. If you really want to use 160mm discs in the rear of your U.P.P.E.R., then Shimano and SRAM flat-mount brakes also offers that option with their dedicated adapter (but as you know by now, we’re not big fans of adapters).for that silly adapter. So that disadvantage is eliminated for OPEN.



For the U.P.P.E.R., we designed a new fork that accepts flat-mount calipers without the need for an adapter. So you can get your Shimano or SRAM flat-mount caliper, remove the standard adapter it comes with, and bolt it directly onto our fork.


This saves weight and increases the stiffness of the braking system.


We do this by making the fork dedicated for 160 mm brake rotors (140 mm is a bad idea anyway on this type of bike) and using the same through-bolt design that is normally reserved for the rear.


Some may not like the exposed bolt heads on the front of the fork leg instead of them being hidden, but we actually like it. It’s a technically superior design, so this engineering choice should be clearly visible.


But the U-turn fork doesn't just save you weight on the flat-mount brake, it is also extremely light itself. At 375 grams, it is by far the lightest fork that fits GravelPlus tires. And to save even more weight, it is comes with an extremely light 12mm Carbon-Ti custom axle


So the U.P.P.E.R. ships standard with the U-turn. Since the U.P. is a post-mount frame, it ships with a post-mount fork, the 3T Luteus II.


Clearance for cross, road and mountain bike tyres, a cross/road position and compatibility with cross/road & mountain bike drivetrains make the U.P. geometry the most complicated we’ve ever worked on. But we’re ecstatic about the result.


Keep in mind that the seattube is designed to be offset, so that your seatpost doesn't have to be. This saves a bit of weight. It also means that the toptube length appears a bit longer than the frame really is, yet another reason why toptube length is a bad measurement to rely on. Best to use stack and reach.


Frame: OPEN U.P.

Frame sizes: S, M, L, XL

Frame weight: 1150g (size L)

Fork: 3T Luteus II Team with 15mm thru axle (included)

BB std: BB386EVO

Chainring fit: Max inner ring: 36t

Max outer ring: 50t (more is overkill with the bigger tyres)

Max single ring: 50t (flat rings, best cassette alignment)

Max single ring: 46t (SRAM 1x offset ring, GXP axle)

Max single ring: 44t (SRAM 1x offset ring, 30mm axle)

Headset std: Integrated Tapered IS42/28.6 | IS52/40

Seatpost Ø: 27.2mm

Rear axle std: 142x12mm thru axle

Rear brake std: Post mount for 160mm disc

Cable routing: Internal via exchangeable MultiStops for 1x10/11, 2x10/11, Di2

Bag mount: 100mm front-post-to-bearing-bore-edge

Incl. in box: Frame, fork, headset, seattube collar, front thru-axle, spare rear derailleur hanger

Frameset Price: £2,230

Unit 9, Hatton Technology Park, Warwickshire. CV35 8XB                  Tel: (+44) 01926 842469


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