Bike Test: Niner Air 9 RDO

As their name implies, Niner Bikes is committed to big wheels. An early adopter of the 29er wheel size, Niner has been pushing the limits of the standard ever since—from minimalist, rigid single-speeds to burly, 5-inch-travel bikes. While Niner’s Air 9 Carbon previously occupied the dreams of cross-country racers everywhere, there is a new sheriff in town, the Air 9 RDO.

RDO is short for “Race Day Optimized,” but that badge may be a little misleading. While this bike will definitely lure diehard cross-country racers, it offers enough amenities to be attractive to trail riders looking for a rocket ship to take them to the top of the climb before their buddies on the weekly group ride.

This bike is essentially a reworked Air 9 Carbon on a diet. Dipping into road bike territory, the RDO’s frame weighs a mere 2.5 pounds, a full half-pound less than the Air 9 Carbon. This new, ultra-low weight is achieved in a couple of ways. First, the carbon layup and materials are more advanced, allowing for a lower weight and stiffer frame. The chunky tubes that scream “Niner” are also scaled back on the RDO. The lower-profile PressFit 30 bottom bracket shell not only means that this bike is intended to be used with a geared setup, but because of the smaller shell, the tube junctions and tubes are smaller. Also, the PressFit 30 bottom bracket does not require an aluminum insert. The tapered head tube also forgoes the aluminum inserts, as the bearing races are now molded in the carbon layup—another trick weight-saving technique.

The rear brake has a new mounting location squeezed in below the chainstay. According to Niner, this resists the twisting forces of braking better as well as making for smaller, lighter mounts.

The question should be, which components don’t stand out? The first thing that caught our eye was the color- matched RockShox SID XX fork with a 15-millimeter thru-axle—very cool. The bike is decked out in Shimano’s XTR group, just like it was in our dreams. The cockpit ties the whole package together with color-matched logos on Niner’s own bar, stem and seatpost.

Moving out: Our 19-inch RDO was on the big side for a large, especially in standover height, while the 16-inch medium, which we tested with the Air 9 Carbon, felt on the smaller side for a medium.

The riders who tested the bike fell between the two sizes. We chose the larger size because of Niner’s input about their frame geometry. According to Niner, their top tubes are a little longer to accompany a shorter stem, which has become somewhat of a modern standard in mountain biking.

Once the rider was underway, the bike’s size was less noticeable and the stem put the bars where we wanted them. The position is forward and aggressive, as is on par for the course for a cross-country race bike. Niner’s flat, 28-inch-wide bar felt right at home on the RDO. Niner clearly had their ears to the ground when they designed their own line of components.

Cornering: The RDO’s frame and fork stiffness provided razor-sharp cornering. Tiptoeing around corners is still possible, but this bike likes to go fast. The harder you attack the trail, the better it performs. The Schwalbe Racing Ralphs spec’ed on the bike provided plenty of grip, and at their 2.25-inch width, they were more confidence-inspiring than their narrower siblings.

Climbing: With a stiff, efficient frame and a build that brings the bike to a mere 21 pounds, the RDO climbs like a goat. No surprise there. The longer top tube allows the bike to stay planted on steep climbs, letting the rider remain seated but providing plenty of room to stand if need be.

Our bike came with a triple-ring crank and an 11-36 tooth cassette that offered plenty of gears to get us up any trail in our area.

Descending: As with most hardtail race bikes, descending at high speed is not for the faint of heart. Experienced riders who are good at finding the smoothest lines down any descent will love how nimble the bike is on the trail. Less experienced riders may find the bike to be a brutal awakening at every wrong line taken, which can be a good learning experience.

With efficiency and light weight often comes a harsher ride. While the Niner is better at cutting down on trail chatter than many carbon hardtails we have ridden, it’s still a hardtail. However, the spec’ed 29×2.25-inch Schwalbe Racing Ralph tires add a bit of comfort due to their large volume.


As we mentioned, sizing on the Niner can be a bit different from other manufacturers. If you are between sizes, we strongly suggest throwing a leg over a couple demo bikes before you make your decision.

The new rear brake mount sandwiched between the chainstay and seatstay may look great and be beneficial in braking performance, but it is a pain to adjust with most multi-tools. If you usually carry a chunky multi-tool on your rides, it will be worth throwing a standard Allen wrench in with your spares in case you need to adjust the caliper.

Niner has a knack for building bikes that not only perform but look good doing it. The RDO lies somewhere between art and performance-driven engineering. The Niner Air 9 RDO does what it sets out to do. It is a race bike, and it is not about to make any excuses or apologies. If you are looking to shave time off of your usual loops or build a super-lightweight race rig, the RDO is an awesome choice.