Open U.P.P.E.R Frameset

Tire clearance

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

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

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

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

There is a second reason we designed for 650b and not 29er tires. 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 tire.

Crank clearance

Behind the bottom bracket, the chainrings, frame and tire all fight for space. And with the need to fit big mountain bike tires 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.

For the U.P. and the U.P.P.E.R., we use different lay-ups, meaning the shapes of the plies and the ratio between the different materials is different for the two models, with the U.P.P.E.R. using an extremely complex lay-up.

Wire-stays

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 2×10/11, 1×10/11 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 entire 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.

Disc brake mounts

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

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.

U-turn

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.

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 and SRAM but also smaller brands like THM and Rotor. 386 EVO even allows for the installation of many mountain bike cranks. Not all versions of each crank fit though, so be sure to check with your local OPEN retailer if you have questions.

Geometry

Clearance for cross, road and mountain bike tires, 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.

As you can see, the chainstays are quite short for a cross/gravel bike, despite the ability to fit the massive 54mm tires in. That’s one of the benefits of the dropped drive-side chainstay.