Singlespeed mountain biking no longer has the fringe status of a decade ago. Many, if not most, brands have at least one model in their line, though most are relegated to low and mid-level offerings.
Options therefore remain fairly limited for riders looking for a purpose-built carbon singlespeed race bike. Niner’s One 9 RDO is one of a select few steeds that cater to the upper echelon of racers who’ve ditched derailleurs (or never learned how to shift).
Ride and handling: precision and stiffness
The One 9 RDO is a true racer’s bike. It’s stiff, precise and translates subtle rider inputs into immediate action.
The frame geometry is orthodox by cross-country standards. With a 100mm fork, the angles measured 71 degrees at the head tube and 73 degrees at the seat tube on our size small test machine.
Niner’s top tube lengths trend long; the 590mm effective top tube on our size small One 9 RDO would be a medium in many other brands' sizings. Chainstay length from the center of the bottom bracket shell is 439mm (17.3in) — neither impressively short nor stretched out; the One 9 doesn't exhibit any handling quirks from the rear end.
Dropper seatposts are not the norm for cross-country riding, though they do make descents more enjoyable
The aforementioned frame stiffness proved a double-edged sword. While it was quick to accelerate each time we stomped on the pedals and quite snappy through turns, it left us wanting more vertical compliance after several hours in the saddle.
Part of this can be attributed to our particular build, as we opted to run a dropper, rather than a rigid seatpost, for the majority of the test. While the dropper added smiles to our miles – dropper posts make every ride more enjoyable – riders thinking about using the One 9 RDO for endurance racing should consider pairing it with a seatpost with a bit of built-in compliance.
It just so happens that Niner makes such a post. We swapped the dropper for Niner’s RDO carbon seatpost. Niner claims the “unstiff carbon layup” of its RDO seatpost deflects up to twice as much as traditional post designs. While we can’t confirm Niner’s numbers, this tester’s derrière can attest to its ability to mitigate high frequency trail buzz.
Frame and equipment: built for 'fun XC' riding
The One 9 RDO is the single-minded analog to the geared Air 9 RDO. Both bikes share similar geometry, with the One 9 RDO getting additional layers of carbon around the bottom bracket shell to handle the higher torque loads generated by singlespeed mashing. Frame weight for our test bike was a very respectable 1,235g.
Niner's BioCentric II system proved silent through several months of pedal mashing
The One 9 RDO is one of three singlespeed models in Niner’s line and the only singlespeed offered in carbon. All of Niner’s singlespeed-compatible models use the company’s proprietary BioCentric II eccentric bottom bracket, which uses two bolts to tighten the two halves of the eccentric against the outside of the frame’s bottom bracket shell.
It’s a very user-friendly system that proved to be silent through the duration of our test. If there’s a downside to eccentric systems, compared with using sliding or “rockered” dropouts to tension the chain, it’s that an eccentric bottom bracket can make it very difficult to fine-tune one’s fit, as the rider’s position relative to the saddle, handlebar and the orientation over the bottom bracket changes fractionally each time the eccentric is rotated.
Our One 9 RDO frame was built up with a hodgepodge of high-end parts that emphasized fun as much as performance. To that end, we opted – as mentioned above – to include an internally routed RockShox Reverb seatpost.
The One 9 RDO has all the modern frame features one expects in a high-end carbon bike, including a 142x12mm Maxle rear end
Upfront, a RockShox SID fork with remote lockout provided 100mm of suspension. Shimano XTR Trail brakes with 180 front and 160mm rear rotors provided faultless stopping power. As for gearing, we alternated between 32:19 for general trail riding and 32:17 for several short-track races.
If you think you might want a singlespeed for most of the time, but don't want to fully commit, you're in luck. The One 9 RDO can also accept a rear derailleur, though it can only be run with a single chainring, adding to its versatility.
If you’re in the market for a high-performance singlespeed race bike that can double as geared 1x11, hardtail the the One 9 RDO should be on your shortlist. Its rigid frame tracks with precision, though it needs a seatpost with a bit of compliance to take the edge off longer rides.
Editor's note: One of our few complaints about the One 9 RDO was that it could only carry one water bottle in the main triangle. After discussions with Niner, we learned that our test bike was a pre-production version and that all production bikes have mounts for two water bottles in the main frame. This review has been amended to reflect this update.