Feel the steel.
One of the most versatile hardtails on the market, the Niner SIR 9 29 5-Star XO1 Eagle Complete Mountain Bike features smooth and supple Reynolds 853 steel construction paired with modernized trail geometry, 29-inch wheels for momentum-carrying speed, and 18 mounting points for bikepacking adventures. Whether you're seeking a steel hardtail for spirited rides through the local mountains or a dependable pack mule for long-distance adventures, the SIR 9 satisfies your itch for exploration with its simplicity, strength, and unmatched versatility. The versatility doesn't stop there, with the SIR 9 swapping the momentum-carrying 29er wheels for the voluminous traction and bump-smoothing feel of 27.5+ wheels. This is especially great, as you can swap tire sizes at a moment's notice for different trail systems and riding disciplines.
It's no secret the bike industry is constantly evolving, so it makes perfect sense that Niner would modernize the previous SIR 9's geometry into something a little bit more trail-oriented. Niner's [R]evolutionary trail geometry makes the SIR 9 longer in the top tube and shorter in the chainstays for lively handling on the trail and a roomier cockpit, which facilitates composure on descents and comfort across long distances. The longer wheelbase of the SIR 9 inspires confidence when you're pushing it at higher speeds on the downhill portion of your ride.
Paired with the FOX 34 Float Factory fork with 120-millimeters of travel, the SIR 9 moves from a rather XC-focused head tube angle of 70-degrees (for the previous model) to a trail-worthy 68-degrees. This gives you added confidence to attack fast descents and technical sections previously on the edge of the old bike's comfort zone. Although it's slacker than before, it still pedals and climbs with resounding efficiency, as Niner engineered it with a steeper 74-degree seat tube angle, which places you in an optimal pedaling position.
Seeing that its name comes from the catchy phrase "Steel is Real," it only makes sense the SIR 9 retains the beloved steel construction for a smooth, compliant ride over jarring trail sections. However, any old steel wouldn't do for the discerning riders at Niner, leading them to use Reynolds 853 steel for its supple characteristics and high levels of strength. Reynolds 853 steel is heat treated and air hardened, meaning the weld zones actually increase in strength after cooling, making them impressively resilient to the stresses and rigors of trail riding. Inside the frame, Niner places a hidden inner-plate that stiffens and strengthens the frame's integrity—all without compromising the steel frame's compliance and supple feel.
This crème de la crème, 5-star build comes with the massive gear range of SRAM's XO1 Eagle 1x12 drivetrain, which ditches a front derailleur in favor of a wide range 10 to 50-tooth cassette. SRAM's Eagle has practically made front derailleurs a thing of the past, seeing you have a larger 500% gear range without having to deal with extra weight or shifting issues. It comes with Stan's Arch MK3 wheelset, which is the go-to choice for enduro racers and aggressive trail riders in Stan's line-up with its 26-millimeter width and dependable alloy construction. The 5-star build is rounded out with a KS LEV Integra dropper post with internal routing for a cleaner aesthetic without exposed cables.
- Niner's most versatile hardtail in steel for supple feel
- Reynolds 853 steel adds compliance for smoother ride quality
- 29er version provides greater speed and obstacle rollover
- Modern geometry for lively handling and long-distance comfort
- Boost axle spacing accepts 29 x 2.5 and 27.5 x 3-inch tires
- 18 total mounts enhance carrying capacity for bikepacking
- SRAM Eagle XO1 1x12 drivetrain provides massive gear range
- FOX 34 Float Factory fork with 120mm of terrain-smoothing travel
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SIR 9 size by rider height
|120mm Travel Fork|
Effective Top Tube
Head Tube Angle
Seat Tube Angle
Bottom Bracket Drop