The Dutchman Gerard Vroomen, known as co-founder of Cervélo and creative lateral thinker in the bike industry, is one of the people behind Open. The highlight of the U.P. is the option of fitting either 28-inch wheels with road or cross tyres or 27.5-inch wheels with mountain bike tyres up to 2.5 inches wide. As the frame and fork are designed for disc brakes and thru axles, the wheels can be swapped without any further adjustments.
Different wheel sizes in one frame? A look at the outer diameter of the different wheel/tyre combinations makes it clear that this is not a crazy idea. A road bike wheel with a 28 millimetre wide tyre has almost the same diameter as a 27.5 inch wheel with 2.1 inch wide rubber. Neither bottom bracket height nor foot clearance between pedals and front wheel change significantly. However, the huge difference between the tyre volumes makes it possible to shift the range of use towards road or off-road, depending on your preference.
To make the concept work, the makers of Open pulled out all the design stops. The right-hand chainstay, which is pulled far down, is not a design gimmick, but a requirement to harmonise the ample tyre clearance with the chain line required for perfect shifting. At the same time, the design means that the rear triangle is much shorter than expected. At 420 millimetres, the chainstays are barely longer than on road bikes and even shorter than on many cross road bikes, which do not offer anywhere near the tyre clearance of the U.P.. The compact design and the weight of just under eight kilos give the bike an agility that you wouldn't expect given the massive wheels. The 2.1-inch tyres fitted to the test bike effortlessly iron out obstacles such as roots or large stones without ever threatening to puncture. The sporty character is emphasised by the race-oriented riding position, which also makes the bike an option for cyclocross riders. The U.P. can be ridden just as well with competition wheels with 33-millimetre tyres, as prescribed by the UCI. However, if you don't care about the competition regulations, you will most likely prefer wider tyres, at least off-road. Every extra millimetre of tyre width dramatically improves the off-road characteristics. With this versatility, the U.P. should provide important food for thought for the further development of the entire gravel bike category.
PLUS Innovative frame concept that allows many wheel/tyre combinations; wide range of uses; well thought-out detailed solutions; lightweight
MINUS expensive
Info up.opencycle.com
Frame material/sizes Carbon / S, M, L, XL
Price/weight 2,900 euros (frame set) / 7.9 kilos
WHAT THE TEST DRIVERS SAY
Jens Klötzer " My high expectations of the bike were exceeded."
Christoph Allwang " All I can say is: pure riding pleasure. The bike can be ridden quickly off-road and doesn't require a high level of steering skill, as the wide tyres forgive almost everything."
Thomas Musch " An amazing bike. Despite the mountain bike tyres, you feel like you're sitting on a racing bike."
Alternatives None so far. Cannondale's Slate is also based on 27.5-inch wheels, but offers less tyre clearance.
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