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Like a crowded rush-hour elevator, there's little elbow room in the 29er hardtail market, as it's quickly being packed with carbon-suited strangers hoping to catch a ride. Unfortunately for the me-too'ers, Niner's already looking down from the top floor with its no-compromises, AIR 9 RDO. And with the smartly spec'd, 2-Star Complete Mountain Bike build, this RDO is ready to rock on a stagehand's budget.

The Air 9 name is shared with Niner's versatile carbon and aluminum hardtails, but the Air 9 RDO is an entirely different animal. The RDO designation, an acronym for 'Race Day Optimized,' clearly states this 29er's purpose -- to place you on the podium. Niner eliminated all excess on this frame and focused solely on making it as light as possible. For example, the rear brake mounts are now cleanly located inside the stays. This reduces the amount of required hydraulic line, while simultaneously making the Air 9 RDO look lean and mean. Also, this frame doesn't use Niner's CYA bottom bracket system. While the CYA is renowned for its versatility, it would add complexity and heft to this purpose-built race machine. So, Niner went with the lighter PressFit30 interface instead. However, the RDO does retain the clean internal cable routing and titanium chain-slap protectors found on the Air 9 Carbon.

The Air 9 RDO isn't just cosmetically and physically different, it's structurally different, too. At the core of every Niner frame is extensive, computer-based finite element analysis, and here, it's used to develop a high modulus carbon fiber structure with optimized weaves, lay ups, and tube shapes. Effectively, this process has produced the lightest Niner to date. The RDO's fluid form is no accident. In fact, it's been designed to dampen chatter and guide impact forces to the stronger parts of the frame. Now, chain torque goes directly to the rear wheel via the large bottom bracket shell and shapely chainstays, yet trail vibrations are quelled by the swooping seatstays. Niner ties the bottom bracket to the strength- and precision-enhancing tapered head tube with a large down tube. This juncture ensures that the frame tracks true and responds to every input.

For precise steering and handling, the 2-Star build sports a RockShox SID RL fork with a 15mm Maxel. The Air 9 RDO rides on an American Classic Terrain Wheelset cased with Schwalbe Racing Ralph 2.25in tires. Driving the rear wheel is a Shimano Deore M590 crankset with 42/32/24t chainrings. They spin a 10-speed, HG62 11-36t cassette with a HG-74 chain. Gear selection is handled by SLX shifters, and front and rear derailleurs. Keeping speed in check is a set of Deore M590 hydraulic disc brakes with 180mm front and 160mm rear rotors. Finishing off the 2-Star build is a handful of alloy Niner components for the handlebars, stem, and seatpost that's been paired with a Niner branded WTB Volt Sport saddle.

The Niner AIR 9 RDO 2-Star Complete Mountain Bike is available in the color Green and in four sizes from Small to X-Large.

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Race Day Optimized

  • Familiarity: I've put it through the wringer

As we all know, the carbon 29er hardtail is the fastest race machine you can buy for most types of offroad racing. Niner has taken their famous Air 9 Carbon a step further and created the ?Race Day Optimized? model for those of us that want the fastest of the fast.

Of the 3 carbon 29? hardtails( Trek Superfly, Santa Cruz Highball, and this bike) I?ve owned lately, I?d have to describe the Niner Air 9 RDO as the quickest handling and most nimble-perfectly suited for the east coast and those tight twisty trails everywhere. It doesn?t have that sluggish 29er feels plaguing most 29ers and quickly responds to any input from the pilot. I also have to say the green is one of the best colors I?ve ever seen on a bike.

Hardtail Heaven

  • Familiarity: I've put it through the wringer

I bought last year's build (2013) after looking at lots of different bikes, some with full suspension. Went on a 7 day hut trip in Colo. San Juan Mountains just two weeks after receiving the bike, during Colorado's epic flood season. We experienced every possible adverse weather condition including rain, cold , hail, lightning, mud, more mud, stream crossings and this bike persevered. Not bad for a bike that is really designed and built for racing. I've been riding it since then and it puts a smile on my face every time. The frame is never harsh and Niner's attention to detail is well deserved. Cables should be internally routed. The rear brake caliper should be hidden where it is less vernarable. Niner does both these things and lots more.

Only gripe is the extremely tight tolerance beween the chain and frame at the crank. When the mud is bad chain suck can happen. But Niner thought of this, too, and put replaceable titanium guards on the frame there. Perfect.

Look no further for the ideal hardtail, well thought out and executed.