Whoops! How did this mountain bike find its way into the gravel bikes section?
With 2.1-inch knobby tires on 650b wheels, the Open U.P.P.E.R. blurs the line between bike segments. Yes, this is technically a gravel bike, and it is an incredibly fun and versatile one to boot.
The U.P.P.E.R. is Open’s latest (and lightest) gravel frame, coming in 220 grams lighter — at 880 grams — than its Classic U.P. frame. That’s lighter than many pure road frames. The U-Turn fork weighs just 370 grams — also impressive. Open attributes the weight savings to different carbon fiber layups as well as flat-mount disc brakes.
While Open continues to shave grams, it hasn’t compromised the geometry that makes the U.P. line so good.
Surprisingly, the bike’s front-end geometry feels a bit like a traditional road frame design, despite the 71-degree head tube angle. We also liked the U.P.P.E.R.’s low bottom bracket (70-millimeter drop), which lends stability to high-speed situations.
Better still, whether you’re riding 650b wheels (as shown here) or more traditional 700c rims with 40-millimeter tires, the bike’s geometry won’t change significantly.
To fit this array of tire sizes, Open shapes the chain stays in radical ways to manage tire clearance and chainring spacing at the bottom bracket junction.
When it comes to adventurous gravel riding, we’ve always liked SRAM’s single-chainring simplicity. The bike we tested actually came with an even wider-range rear cluster to match the Force 1 shifters. E Thirteen’s TRS cassette has a 9-46-tooth range. Combined with a 40-tooth front chainring, the bike is always eager to climb. The fact that it all weighs less than 17 pounds made a big difference, too.
The DT Swiss Spline 1200 wheels certainly contributed to the bike’s lively feel. The carbon rims have hookless beads, which should make for better durability, and they are wide (30-millimeter internal width), affording more tire volume.
A few of Open’s other component picks were less successful. The 3T handlebars seemed too narrow for all-terrain riding. The carbon seatpost, also by 3T, made for a comfortable ride, in part due to the 27.2mm diameter. Unfortunately, the two-bolt head was a bit creaky.
Schwalbe’s G-One tires have a low-profile tread pattern that helps make this bike more versatile. They’re a compromise between speed and traction — the stubby side knobs don’t offer a ton of cornering grip, and we did slash a sidewall during a test ride.
Fortunately, since Open usually sells U.P.P.E.R. bikes as framesets, you can pick and choose your parts. Better still, the frame design allows you to get wild with knobby mountain bike tires or stick to a standard 700c gravel configuration.
Outfitted with wide 650b tires, our test U.P.P.E.R. had a fun personality. Apart from the drop bars, it felt a lot like a cross-country race bike, encouraging us to find unusual routes that combined trails and roads.
On the pavement, we could keep up with friends on ’cross bikes, but it was slower. Once we veered onto a rocky jeep road, however, the traction and cushion afforded by bigger tires was a clear advantage.
The biggest drawback is that the versatility doesn’t come cheap. If the U.P.P.E.R. is outside of your price range, a Classic U.P. frameset starts at $2,600.
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