Introduction

In 2012 we introduced the O-1.0; the world's first sub-900 gram hardtail. It was the perfect XC racing machine as our customers (you!) have proven that time and time again, from World Cup cross country races to Cape Epic wins (without sponsorships!)

By mid-2015, we were almost ready to introduce the ONE, but a delay in manufacturing and the introduction of the Boost standard made us change our mind. Boost increases wheel & frame stiffness and improves tire clearance. This was too good a chance to pass up, and so we reworked the frame completely into what is now the ONE+

The ONE+ is still that zero-compromise XC racing machine; our customers expect this from us and so we made absolutely no compromise here. Boost, a BB92 bottom bracket and our Thru-Thread thru axle increase drivetrain stiffness further, while new Wire-stays improve vertical compliance & traction. A dozen more tweaks and updates make the ONE+ a much, much better frame than we ever thought possible.

And then the bonus: Boost gave us enough space for 29x2.4” tires and tons of mud clearance, perfect for the ever more demanding XC courses. And similar to what we did on the U.P. the ONE+ also provides space to put in a 27.5x3.0” tire! While there are other frames that offer to fit both wheel sizes, they are usually heavy and not that much fun. Because the ONE+ has a zero-compromised XC frame that is still sub-900 gram, it’s super light not only as an XC racer but also as a 27.5+ tire go-anywhere bike. This makes it not only an interesting option for tough, fun rides but even for very demanding XC courses. More tire, more fun, more speed!

Tire philosophy

The ONE+, like its predecessor the O-1.0, is all about agile handling and efficient power transfer in a super-light package. For the new design we made two small tweaks:

With the cross country geometry dialed in, we focused on a third, much tougher change: how to offer the option of fitting 3” wide tires onto such a cross-country racing machine without compromising the handling.

We faced a similar problem for the U.P. model, and the solution is also similar. Had we simply made space in the frame for 29er tires that are 3” wide, the resulting bike would have been a disaster for two reasons:

Obviously this was not an option for us; we do not wish to compromise the cross-country handling of the frame at all.

So we went a different route. For the 3.0” tires, we went with a 27.5” rim (26” for size S). The smaller radius of this rim in combination with a bigger tire renders the same overall wheel size as a bigger radius rim with a smaller tire.

Same overall wheel size, same handling, no compromise. That simply doesn’t work with 29x3.0” Plus tires, only with 27.5x3.0” Plus tires. Here it is in numbers:

Boost

Lots of confusion in the mountain bike world nowadays, between three wheel sizes, several axle standards, Fat & Plus tires, Boost, etc.

So let’s talk about Boost. It’s really quite simple, Boost moves the chain outward by 3mm without changing the Q-factor (pedal stance) of the crank. It basically uses up the space created when high-end bikes stopped using triple cranks.

Also moving the cassette out 3mm plus another 3mm on the disc brake side means the rear wheel axle grows from 142 to 148mm. This improves the angles for the spokes to create a stronger, stiffer wheel. Great for big 29er wheels but really a good thing for every wheel size.

Bottomline: same pedal stance/Q-factor up front for good pedalling efficiency, wider spoke stance in the rear for stiffer, stronger wheel builds. If you want, you can also do the same trick in the front with a Boost front hub (110mm vs 100mm) but that’s optional.

Why do we add Boost to this frame? Because it adds stiffness to the build, because it works well with the wider rims that we prefer and because it creates more tire clearance between tire and chain. Aside from these advantages, there really aren’t any drawbacks now that all manufacturers have started making their components in Boost versions.

Dropped chainstay

To create space for bigger tires, the ONE+ features OPEN’s trademark dropped chainstay. A clean and simple method to move the chainstay away from the most crowded real estate on a frame and towards an area where we can boost the chainstay size for the most efficient power transfer.

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.

Wire-stays

The rear triangle has to provide lateral stiffness for an efficient drive train, but vertical compliance for better comfort. The ONE+ features chainstays and seatstays that are extremely thin vertically to provide that compliance, while their lateral width and layup ensure rock-solid propulsion.

The seatstays are pre-curved so they can absorb even small bumps very quickly. But lay the bike into a turn and you’ll notice how stiff they are laterally. 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).

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 ONE+ 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.

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.

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 ONE+ uses a 92mm bottom bracket standard. This allows you to directly mount a Shimano or SRAM 24mm crank in the frame (the wider BB shell replaces the outboard bearing cups, essentially integrating them into the frame structure).

You can even fit cranks with wide, 30mm axles by using a special super-light bearing set (for example the THM M3 and RaceFace SL cranks) for the stiffest, lightest possible set-up.

Geometry

PLEASE read this before you jump into the numbers, so at least they make sense:

1. The geometry is based on an unsagged 100mm suspension fork
2. The size Small is designed around smaller wheels and hence a shorter fork. If you size by stack & reach, this doesn’t matter as they are independent of wheel size. But if you look for example at headtube length, you will see “strange” things like the Small having a longer headtube than the Medium. That’s not because the Small is taller, but because the whole headtube starts lower because of the smaller wheels.
3. The ONE+ is designed around narrow 29er cross-country tires and wide 27.5” “semi-fat” tires. Both have very close outside wheel diameters so the geometry doesn’t really change between one or the other. Of course there will always be small differences from one tire to the next, a 2.1” tire from Schwalbe has different dimensions (in width and diameter) than a Continental or WTB. And of course a 2.4” tire will be slightly different from a 2.1” even if the make and model are the same. ll these dimensions are also affected by rim width. For the handling, that all falls within the range that we design for, but you do have to realize that for example standover height is slightly effected by this. This is obviously not unique to the ONE+, this applies to any bike.
4. Standover height is measured to the top of the toptube directly above the bottom bracket and depends slightly on the exact tire size used.

size

standard
wheel

semi-fat
wheel

stack

reach

headtube
angle

seattube
angle

fork
axle-crown

headtube
length

toptube
length

seattube
length

BB
drop

rear
center

front
center

wheelbase

standover
height

S

27.5"

26"

584

401

71.0°

73.0°

487

102

576

420

40

423

635

1056

728

M

29"

27.5"

615

419

71.4°

72.5°

506

97

602

445

57

440

655

1092

752

L

29"

27.5"

647

436

71.4°

72.0°

506

135

643

500

52

440

684

1121

809

CUSTOMER BIKE SHOWCASE

One of our favorite aspects of OPEN is how many customers we are in regular contact with. Often the discussion will involve bike spec, leading to many very interesting builds. Below you can find them, and if you haven’t uploaded your build already, we’d love to see it.