Test review from CYCLIST magazine

The spec Model Open UP (Unbeaten Path) Groupset Sram Force 1x Deviations None Wheels Hed Ardennes 650b Finishing kit Enve Compact Road handlebar, Enve Road stem, Enve inline seatpost, Fizik Antares R1 braided saddle Weight 7.9kg Price £2,230 frameset Contact

In the beginning there was the road, and there was the road bike, and the road was good. Then consumers wanted to ride on more exotic terrain, without venturing into mountain bike territory, and thus the ‘gravel bike’ was born.

Gerard Vroomen, co-founder of Cervélo (alongside Phil White) has taken things further. His brand, Open Cycles, developed the UP (Unbeaten Path) to do away with categories: ‘People see in the UP whatever type of riding they like to do. That’s how it was conceived.’

Vroomen says the UP, despite appearances, is no road bike. He defines it reluctantly as GravelPlus – a bike that’s designed to be ridden quickly, but can handle all terrains.

It’s built around 650b wheels – smaller diameter rims, closer to the size of 26-inch mountain bike wheels than the 700c road wheels we’re all so used to. Open noted that a 650b rim with a 2.1-inch mountain bike tyre has nearly the exact same circumference as a 700c rim with a 28mm tyre, meaning the UP preserves the geometry and feel of a road bike. Plus, because it uses disc brakes rather than rim brakes, the UP’s wheels can be freely switched between the off-the-peg 650b wheelset and any normal disc-equipped 700c road wheel. With wide clearance at the rear and front, any variety of tyre size and width can be used.

Open isn’t the first to release a bike with such versatility, but it stands out as an innovator. Hed’s own Triple Crown frame was designed to do exactly the same wheel switch between 650b and 700c wheels, while Cannondale’s Slate was also designed around 650b wheels. However, the Triple Crown is a fairly weighty touring-minded steel frame, while the Slate is limited by its Lefty suspension fork – there are currently no specific compatible 700c road wheels available. Crucial to the UP though is the design of the chainstays, engineered to a tight 420mm length to give sharp, racy and consistent handling across all wheel types (see The Detail, below).

The idea is that the bike should be as comfortable riding rough trails as it is on the tarmac, but Vroomen reiterates that reserving it for the road would be like ‘keeping a lion in a cage in your apartment’. So with respect to Vroomen, I tested the UP on a variety of terrains, but also rode it on the road just as much as I would any normal road bike. The result was startling.

Eye catcher

I was stopped a total of 12 times in my first week of riding the Open UP. Road riders, mountain bikers, pedestrians and motorcyclists all stopped me to ask about the bike and compliment its unique looks. What drew attention wasn’t just its striking colour, or the oddity of its 2.1-inch wheels, but possibly the fact that the UP is surprisingly rapid, despite its wide tyres.

Riding the UP is an education in tyre pressure. The balance between grip and speed becomes palpable. At a relatively high 60psi (for 2.1-inch tyres), the bike zips along happily, and I found myself cruising with ease on the flats at around 30kmh. Once you go above 40kmh, friction does seem to get the better of the equation, and holding speed becomes a real effort. At any speed, though, the amazing thing about the UP is that it feels fast. Partly the small wheels, partly the stiff frame, and partly the light overall weight means that it accelerates unnaturally quickly for its size – a little like a lightweight Brompton spinning away from a set of lights. It just feels animated and alive in a way that few other bikes can achieve without feeling wildly uncomfortable.

Even when I did puncture, the tyre self-sealed with