One smooth ride.
One of the most versatile and smooth-riding hardtails on the market, the Niner SIR 9 27.5+ 3-Star XT Complete Mountain Bike features the supple characteristics of Reynolds 853 steel construction paired with modernized trail geometry, 27.5+ wheels for massive traction and rock-smoothing compliance, and 18 mounting points for bikepacking adventures. Whether you're seeking a steel hardtail for spirited rides in the mountains or a dependable pack mule for long-distance adventures, the SIR 9 satisfies your itch for exploration with its simplicity, strength, and smooth-riding characteristics. Making it even more versatile, the SIR 9 easily swaps the included 27.5+ wheels for the momentum-carrying abilities of its 29-inch brethren. This is especially important, as it lends adaptability for varying trail ecosystems and riding disciplines.
By now, you're probably aware the bike industry is constantly pushing the envelope on geometry, with things becoming slacker and longer to accommodate aggressive riding styles. The SIR 9 eagerly follows this modernized trail geometry with its longer top tube and shorter chainstays, which make the bike's handling all the more lively around corners and stable at high speeds. The wheelbase is longer as well, inspiring you to push the envelope when it comes to carrying speed on extended descents.
Paired with the provided 120-millimeter Reba RL Solo Air fork, the SIR 9 moves from a rather XC-focused head tube angle of 70 degrees (on previous model) to a trail-worthy 68 degrees. This gives you added confidence to attack steep descents and technical trail sections previously on the edge of the old bike's comfort zone. Although it's slacker than ever, 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.
It's no surprise the SIR 9 retains the supple ride quality of its Reynolds 853 steel construction, especially seeing its name stands for "Steel is Real." Any old steel wouldn't satisfy the discerning riders at Niner, prompting them to construct the SIR 9 of Reynolds 853 steel, which provides compliance and dependable strength on the trail. 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 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's smooth, supple feel.
This particular 3-star build with 27.5+ wheels comes with the reliable shifting and wide gear range of a Shimano XT 1x11 drivetrain. This 1x11 drivetrain offers a massive range of usable gears with its 11- to 46-tooth cassette ensuring plentiful low-end for powering yourself up climbs. The brakes follow suit, with Shimano XT disc brakes doing an admirable job of stopping you in a hurry. The wheels are sourced by Stan's NoTubes, with their Baron S1 wheelset providing a 35-millimeter width for running 2.8-inch Maxxis Rekon+ tires. Rounding things out, you'll find a KS LEV SI dropper post for adjusting saddle height on-the-fly, complete with internal routing to keep it looking clean.
- Niner's most versatile hardtail in steel for supple feel
- Reynolds 853 steel adds compliance for smoother ride quality
- 27.5+ wheels bring voluminous traction and bump-smoothing ride
- Modern geometry for lively handling and long-distance comfort
- Boost spacing accepts both 29 x 2.5 and 27.5 x 3-inch tires
- 18 total mounts enhance carrying capacity for bikepacking
- Shimano XT 1x11 drivetrain with wide range 11 to 46t cassette
- RockShox Reba RL Solo Air fork with 120-millimeters of 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