Open's distinctive, bright orange UP (which stands for Unbeaten Path) combines a light and stiff carbon fibre frame and fork designed explicitly to perform on dirt and gravel with huge tyre clearance, so you can fit just about any tyre you want including mountain bike options. It's packed with nicely executed design details, but it does command a high price.
The Open is a bike you can ride pretty much anywhere. The same can be said of a growing number of gravel and adventure bikes, of course, but where the Open scores highly is in that huge tyre clearance. Everything from 28mm slicks for road riding to 38-40mm gravel-specific tyres, 47mm-wide 650Bs and even 2.1in mountain bike knobbly tyres fit inside the cavernous clearance front and rear.
I found a 38-40mm low profile gravel tyre like the new Hutchinson Overide or Panaracer Gravelking the best fit for the sort of riding I was doing with the Open, predominantly off-road with interlinking road sections. That's the beauty of the Open, you can build it up with the tyres that suit your riding style and intentions.
Make your tyre choice and take the Open off-road onto gravel roads or narrow bridleways and the bike instantly feels at home. The geometry gives the bike a measured stance, with the slowish steering ensuring it never feels nervous or twitchy when the tyres are scrabbling for grip or you're screaming down a loose and fast descent. While the stability makes it an easy bike to travel fast across rough terrain, there's a lively edge to the Open's handling when you ask for it, and it nips and tucks through corners and carves beautiful turns with solid ease.
Where the geometry really shines is in just how far you can push the Open in tricky and technical terrain. Its limits far exceed that of a cyclo-cross bike, especially if you go to as wide a tyre as you can fit in the frame, and there's no need to tip-toe over roots or rocks, you can charge full bore through and over them. I was able to ride many of my easier mountain bike trails on the Open, not something I've ever tackled before on a road bike.
It's a comfortable ride too, for long periods in the saddle. The skinny stays and 27.2mm seatpost help to provide noticeably more isolation from trail chatter and vibrations than an aluminium alternative such as Mason's Bokeh, to pick one example. It really looks after you on long rides, and you'll feel as fresh as can be expected when riding a lightweight carbon bike with no suspension other than large volume tyres across rough terrain...
It's not only in off-road situations that the Open shines. Swap the knobbles for slick tyres – I went for a 28mm – and its road riding manners prove to be more than adequate for long rides. It's not a full-fledged road bike, but the carbon frame and fork, along with the oversized bottom bracket and large profile chainstays and down tube, give the Open a high level of stiffness. This makes it responsive when you inject some pace into proceedings, and it fairly belts along the road. It's quick enough that you can keep up with your buddies on road bikes most of the time, though some deep-section wheels would certainly add some extra oomph.
Transitioning from the road to off-road, with a focus on exploring the 'unbeaten path' – to use the bike's full name – is what it does so well. With the right tyre you can ride anywhere and over everything and not feel overly compromised at any point. You're not constrained by the terrain and this results in huge smiles – it's the most fun bike I've reviewed in ages.
The full carbon fibre frame and fork are beautifully finished, and not just because of the orange paint... Designed by ex-Cervelo founder Gerard Vroomen (also responsible for the more recent 3T Exploro), the 55cm frame here weighs 1,150g, which isn't bad for a bike designed for rugged off-road riding.
It's packed with interesting features and nice details and really does stand out from the crowd (and not just because it's bright orange...). By far the most intriguing is the dropped drive side chainstay. It's shaped this way to provide the necessary tyre and chainset clearance while keeping the Q-factor narrow and the chainstays short. It's something we've seen on mountain bikes, and a few other road bike brands are starting to adopt a similar approach.
Other details include a tapered head tube, BB386 EVO bottom bracket and full internal cable routing, compatible with any combination of mechanical or electronic gears, hydraulic brakes and 1x or 2x chainsets thanks to Open's MultiStop system of inserts.
The down tube has flattened sides, said to improve frame stiffness, while the seatstays are pencil thin which, in unison with the 27.2mm seatpost, should provide a reasonable level of comfort. To ensure the correct amount of seatpost is installed, there's a tiny SafePost Pilot hole near the top of the seat tube.
It's a disc brake-specific frame using the post mount standard and thru-axles – 142x12mm at the back and 15x100mm at the front.
This is the only area where the Open UP has been slightly overtaken by the rapidly changing standards in the time since it was launched, with flat mount and 12mm front thru-axles increasingly looking likely as the de facto choice. Still, there's nothing actually wrong with post mount or 15mm thru-axles of course.
As well as two regular bottle cage mounts, there's a third on the down tube, which would also serve as a handy place for a tool keg.
There are also two bolts on the top tube for fitting a top tube bag but actually getting hold of a compatible bag provide a tad tricky, and with the prevalence of strap-on top tube bags, I simply removed the bolts, slapped on some helicopter tape, and used a top tube bag.
There's a lot of versatility baked into the Open UP, but the one detail it's arguably missing is the addition of mudguard mounts that would ensure it meets the needs of the all-weather British cyclist.
This is a frameset review because Open doesn't sell complete bikes, so I won't go into too many details on the equipment. Suffice to say, I used a SRAM Rival 1 groupset that is an ideal option, with the simplicity of the single ring drivetrain (I chose a 38-tooth) and a wide range 11-36 cassette offering all the gearing I needed – especially when it came to tackling the climbs of the Dirty Reiver course. You can, of course, fit a much wider range cassette.
The low-focused gearing was fine off-road and adequate on the road, but you do spin out more easily on descents. A switch to a bigger chainring is an easy solution – or you could simply freewheel when it gets that fast and use the descents to recover ready for the next climb.
I swapped the rest of the parts out loads during the test, changing wheels a few times but settling on the excellent Praxis RC21 carbon tubeless wheels. They have a wide profile rim that works nicely with wide tyres, tubeless installation is easy, and they proved durable and tough.
The rest of the kit included a carbon Bontrager bar, Ritchey stem and Enve seatpost, plus a Fabric saddle and Fizik bar tape. I used an Apidura framebag for the Dirty Reiver and covered the frame in helicopter tape to prevent it from getting scratched.
There are a lot of rivals operating in the same gravel/mixed terrain space as the Open UP, and more affordable complete bikes with similar purpose and poise, such as the £2,900 GT Grade and £2,600 Specialized Diverge. At £2,000 the complete Raleigh Roker Pro is less than the Open UP frame and fork.
The £3,100 Mason Bokeh runs the Open UP close in terms of performance, but the Open UP edges it in pure agility and smoothness.
If you look at the Open UP as two bikes in one with just a change of tyres or wheels, the premium price tag is a little easier to justify. Putting the price to one side, the UP is a beautifully made and finished product, packed with smart design features and offering a level of performance for off-road and mixed terrain riding that ensures it's one of the best options in the gravel/adventure category.
Superb multi-terrain adventure and exploration bike – if you can afford it
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road.cc test report
Make and model: Open UP gravel/adventure bike
Size tested: 55cm/M
Tell us what the frameset is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about the bike?
Open says: "U.P. (Unbeaten Path) combines a performance-oriented road geometry & parts with clearance for mountain bike tires. Start on asphalt, hit the gravel, switch to single track. Its geometry makes you fast; its tires unstoppable.
"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!
"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.
"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
"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.
"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."
State the frame and fork material and method of construction
Frame: OPEN U.P.
Frame sizes: S, M, L, XL
Frame weight: 1150g (Large)
Fork: 3T Luteus II Team with 15mm thru axle (included)
BB std: BB386EVO
NOTE: For single chainring set-ups, we recommend flat rings, not offset rings, for the best chainline. For "regular" oval rings, deduct 2 teeth from the below spec. For extreme oval rings, who knows. Max inner ring: 36t
Max outer ring: 50t (more is overkill with the bigger tires)
Max single ring: 46t (offset rings like SRAM 1x)
Max single ring: 50t (flat rings, better cassette alignment)
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 & rear thru-axle, spare rear derailleur hanger
Tell us about the build quality and finish of the frame and fork?
Open uses the "right carbon in the right spot" it says, in a process it calls TRCinTRS. "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."
Tell us about the geometry of the frame and fork?
Similiar to a cyclo-cross bike but with shorter chainstays and a lower bottom bracket.
How was the bike in terms of height and reach? How did it compare to other bikes of the same stated size?
The 55cm size frame fitted well, and the position is on the long and low side compared with some bikes with a higher stack.
Riding the bike
Was the bike comfortable to ride? Tell us how you felt about the ride quality.
The carbon frame and fork provided a very smooth ride over rough terrain, nicely soaking up impacts and vibrations.
Did the bike feel stiff in the right places? Did any part of the bike feel too stiff or too flexible?
The oversized bottom bracket and main tube profiles give the UP plenty of stiffness when putting the power down.
How did the bike transfer power? Did it feel efficient?
Very well for a gravel/adventure bike.
Was there any toe-clip overlap with the front wheel? If so, was it a problem?
None at all.
How would you describe the steering? Was it lively, neutral or unresponsive? Relaxed.
Tell us some more about the handling. How did the bike feel overall? Did it do particular things well or badly?
It's relaxed at high speeds and nimble at low speeds, a very well balanced ride over mixed terrain.
How did the build components work with the frame? Was there anything you would have changed?
I was happy with the equipment I built up the frame with, the SRAM 1x11 groupset is a good choice for this style of bike.
Did you enjoy riding the bike? Yes
Would you consider buying the bike? I did consider buying it very seriously.
Would you recommend the bike to a friend? Yes
Use this box to explain your score
The Open UP might just be the best adventure bike I've ridden, and it easily earns a high mark, but the price is tough to swallow.
About the tester
I usually ride: My best bike is:
I've been riding for: 10-20 years I ride: Every day I would class myself as: Expert
I regularly do the following types of riding: road racing, time trialling, cyclo-cross, commuting, touring, mountain biking
David has worked on the road.cc tech team since July 2012. Previously he was editor of Bikemagic.com and before that staff writer at RCUK. He's a seasoned cyclist of all disciplines, from road to mountain biking, touring to cyclo-cross, he only wishes he had time to ride them all. He's mildly competitive, though he'll never admit it, and is a frequent road racer but is too lazy to do really well. He currently resides in the Cotswolds.