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'Fastest Singlespeed Mountain Bike In World'

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It costs $2,149 for the frame — just the frame. But Niner’s ONE 9 RDO is designed to be the fastest singlespeed mountain bike in the world. It is a simple, lean, and efficient machine. And it is indeed fast.

We got one in house and built it up with the industry’s best parts. And then we unleashed it on the elite mountain bike racing circuit.

We’ve built it up as both a singlespeed, and as a geared bike, and we have figured out which is better.

ONE 9 RDO frame

The ONE is a unique machine. It lacks a front derailleur mount and has been subjected to (Niner’s words) “extensive computer aided optimization” to result in a bike tailored for a single chainring up front.

The oversized CYA bottom bracket shell and chainstays bulge wide into the space where a normal mountain bike has its small front rings. The design transfers energy exceptionally well without a weight penalty.

The frame uses high modulus carbon fiber in some places and oversized tubes to get the frame weight down to a super-low 1235 grams.

The ONE differentiates itself from some other frames with a bottom bracket design that eliminates the adjustable rear dropout. It allows adjustment of the drive line length at the crank (not at the rear dropouts), providing an easy to adjust system for running the bike in singlespeed configuration. Niner’s “Biocentric” bottom bracket allows for easy adjustments to gears, eliminates chain tensioners, and also eliminates brake adjustments with gear changes. It also allows for the use of a rear through axle. The ONE is the only Niner hardtail to get the rear through-axle, as the AIR9RDO still uses a quick-release.

Niner’s biocentric bottom bracket eliminates adjustable rear dropouts

The ONE is an awesome singlespeed machine. The massive torque a strong rider uses to climb a hill, particularly at low RPM in a standing position, demands a frame that converts those massive twisting forces into forward energy. The ONE does this better than any other bike we’ve tested. It’s a light and stiff monster. The frame bulges around the bottom bracket. Chainstays are wide and stout, bracing against the low speed torque of a flexing singlespeed rider.

Massive 15mm through axle, instead of rear drop-outs

The bike has a 15mm rear through-axle, which you won’t see on other singlespeed bikes. As a singlespeed, the bike can be built up well under 17lbs, as shown in the picture at the top of the story, with an XTR build at a lustworthy 16.75lbs. Worried about pushing a big gear up a hill? It’s a lot easier when your mountain bike is this stiff, and weighs half the weight of other mountain bikes.

CYA bottom bracket shown with BB30 cups installed

The bike feels awesome in the corners, because it is comfortable at the limits. Niner was the first to get the advantages of the big 29-inch wheels figured out, and the geometry of this bike races really well.

No other bike feels as confident entering a singletrack turn. One modification we find necessary is to find a stem with an extreme drop if you build it up with a suspension fork with 100mm or more of travel. The frame is designed around an 80mm or 100mm front fork, but we felt the 100mm necessitates the use of an aggressive drop if you are going to get enough weight over the front wheel.

After a spring built as a singlespeed bike, we threw SRAM’s awesome XX1 driveline onto the frame because we wanted gears for the race season. In a geared configuration the bike also worked well.

With gears

The ONE is the ultimate singlespeed by nearly any measure. As for it being the ultimate geared bike… it’s damn close, although not quite there. We would choose a number of geared bikes ahead of the “ONE”, including Niner’s own AIR 9 RDO, as it is about 100 grams lighter and is more compliant.

But it does deliver huge stiffness, hardly any weight penalty, great looks, and awesome engineering. We don’t want to send this one back after the test. This is hardtail nirvana.

—Tom Puzak is a contributing editor.

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