Review: Niner Air 9 Carbon

By Shannon Mominee

Niner is best known for their steel and aluminum frames built around 29” wheels. Chris Sugai and Steve Domahidy of Niner envisioned building a carbon fiber frame too, and worked out the engineering process for over two years as the company grew. They focused the majority of that time on tube shapes and lay-up patterns that would deliver a high ride quality, while taking into account the stresses associated with 29” wheels, to design a frame that was strong, light and unique. The resulting frame is the Air 9 Carbon, which shares the same geometry as their other hardtails, but kicks their ass structurally and aesthetically.

The Bike

The monocoque design has alloy interfaces around the bottom bracket and headset for added strength, while the 1-1/2” to 1-1/8” tapered head tube, large hexagonal down tube, and bottom bracket area increase torsional rigidity and lateral stiffness. The frame is compatible with 80mm or 100mm forks; my tester arrived with a paint-matched 100mm Niner carbon fork (reviewed in issue #148) and a 100mm RockShox Reba XX Dual Air 29 with hydraulic remote lockout system.

The oversized bottom bracket shell uses a choice of Niner’s C.Y.A. inserts to be compatible with most major BB standards (threaded external bearing, BB30, PF30, BB92), as well as Niner’s Bio-Centric BB, a new take on the eccentric BB. It’s a two-piece design: each half slides into the BB shell, and a tension bolt, screwed in from the non-drive side, aligns and clamps the BB housing from the sides. This design allows for adjusting chain tension or BB height by loosening the tension bolt and rotating the entire unit to the desired position, then re-tightening the bolt. Because the crank arm tension is so low, it’s not necessary to loosen the arms for the Bio-Centric BB to rotate. Niner’s claim is that compared to a standard EBB, the Bio-Centric has an increased offset for chain tensioning over a wider gear range, plus better sealing properties. From a user standpoint, its single-bolt design makes it simple to adjust.

Replaceable dropouts, available with or without a derailleur hanger, keep the Air 9 Carbon looking clean when built as a singlespeed. In geared form, the head badge doubles as derailleur housing stops for the internal shifter cable routing. Plugs are included to disguise the holes when not in use.

The bike arrived as a singlespeed with the Hive e-Thirteen XC Single Speed Crankset and 32x20t gearing. Stan’s ZTR Crest 29er rims laced to DT Swiss 240s hubs with Schwalbe Racing Ralph 29”x2.25” tires, Formula R1 brakes with 160mm rotors front and rear, Niner carbon bar, and Thomson stem and seatpost rounded out the build. All are quality components, and with the carbon fork, Stan’s sealant, and XT pedals installed, it added up to 18.2lbs.

From Kiwis to Punk Bike

My plan was to take the Air 9 Carbon to New Zealand, explore some trails, and ride the 2010 Singlespeed World Championships that were held in October in sunny Rotorua. With a 100mm fork, the bike’s 71° head and 73° seat tube angles put me in a comfortable position that wasn’t overly aggressive and felt natural. On the trail it rides light and firm, reacting to steering input quickly. The 43.7” wheelbase helped me slice and dice around roots and rocks. When I used the rigid carbon fork, it supplied real trail feedback.

The large head tube, shaped down tube, and oversized bottom bracket keep the frame in a solid plane, and as far as I could tell, there’s not much, if any, twisting or flexing. The carbon frame is definitely stiff laterally, but with Niner’s lay-up pattern, carbon’s damping qualities, and 22psi in the big wheels, the ride was as smooth as can be. I felt no loss of energy or momentum as I pedaled and either ran over or bounced across obstacles.

The 17.3” chainstays tuck the rear wheel close to where my body weight rests to help maintain traction during out-of-the-saddle climbs. Likewise, Niner’s 701mm-wide carbon bar gave plenty of leverage, and with the stiffness of the frame, became the perfect platform for rear wheel power transfer when mashing the pedals and pumping the bar to ascend steep hills.

Heading to New Zealand, I wasn’t sure what terrain to expect, so I installed the Reba XX Dual Air fork, which along with inner tubes and my saddle bumped the weight up to 21.4lbs. I rode a variety of hilly terrain there, so RockShox’s hydraulic remote lockout became invaluable. It was great to be able to put the bike back into rigid form with a push of the thumb. I used the remote frequently, but it held up and still feels fluid.

At Woodhill Bike Park, it seemed easy to maintain a line on the wooden features and pedal across skinnies with no flex in the frame. I confidently took 3’ drops and held speed through the corners, even as it began to rain. Formula’s R1 brakes felt awesome, stopped as needed, and the pad contact adjustment was a welcome upgrade (I tested the RX in Issue #149).

During the 2010 SSWC, I always took the course options marked “Fast and Hard” and held on as the wheels picked up speed. The faster the Niner goes, the more alive it seems, whether leaning into curves, pushing back and taking drops, or coasting downhill and maintaining momentum for the climb. Wherever I rode this bike I felt at home and not limited by the single gear.

On the complete opposite end of the riding spectrum (and the globe), I used the Niner during Dirt Rag’s Annual Punk Bike Enduro. The rear triangle managed mud well during this December slop-fest, and my rear wheel kept spinning where other riders were stopping to remove mud from their frames. Only when I stood at a beer break did the mud freeze to the frame and give me trouble.

’ve heard of others plagued with creaking sounds around the BB, but through sand, gravel, dust, snow and mud, the Bio-Centric BB hasn’t developed any noises for me. It has, however, slipped multiple times, lessening the tension on the chain. Niner advised me to put a little grease on the end of the 6mm bolt to prevent it from binding, which gives a false reading when applying the required 190in-lbs. of torque. On the bright side, the chain easily adjusts with a 6mm hex wrench and about two minutes of time.

Final Thoughts

The Air 9 Carbon would adequately satisfy the racer looking for a lightweight singlespeed, and, in fact, Garth Weinberg won the 2010 SSWC riding this very bike. Likewise, XC riders and occasional racers that want a nice-handling, quiet singlespeed that can be ridden comfortably all day should test-ride this bike. And anyone looking for a geared carbon hardtail with an interest in converting to singlespeed would benefit from the Niner. If I had the cash, I’d keep this bike. It looks good, rides solid and has been an all-around pleasure.


Country of Origin: China

Price: $4,330 w/carbon fork, $4710 w/RockShox Reba XX, frame $1,900

Weight: 18.2lbs. w/carbon fork, 21.4 w/RockShox Reba XX

Sizes Available: S, M, L (tested), XL


Tester: Shannon Mominee

Age: 37

Height: 6′

Weight: 180lbs.

Inseam: 33”


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