SIR 9 27.5+ 2-Star Complete Bike
There's a very good reason why many custom frame builders use steel to this day. Premium steel alloys, like Reynolds 853, are revered for their strength and ability to add a springy, lively ride. When you put that material in the hands of the mountain bike maestros at Niner, you can bet you'll get modern trail geometry, the ability to run 27.5+ or 29-inch wheels, and a bevy of mounting points for bikepacking adventures. So if you're looking to get back to your steel hardtail roots or a new riding buddy for all-day and overnight adventures, the SIR 9 27.5+ 2-Star Complete Bike gets you simplicity, strength, and unmatched versatility. We love the ability to run the voluminous plus tires in this configuration for flotation and grip over loose and chunky terrain and with a simple wheel swap, you can change the ride to momentum-carrying 29er wheels for maximum roll over and mile munching.
As mountain bikes continue to evolve, Niner took it upon itself to modernize the SIR 9's geometry into something a little bit more trail-oriented. Niner's [R]evolutionary trail geometry makes the SIR 9's reach a bit longer while shortening the chainstays for snappy handling on tight trails and more stability with its roomier cockpit, giving it more composure up and down the trail and at high and low speeds. The slightly longer wheelbase inspires confidence on steep, rough downhill portions of the trail allowing you to ride terrain typically reserved for full suspension bikes.
Up front, a RockShox Judy Gold RL Solo Air fork with 120-millimeters of travel gobbles up the terrain and kicks the head tube angle to a very trail-worthy 68-degrees. This provides the chops to attack fast descents and technical sections with more confidence than typical XC hardtails. That slackness up front doesn't sacrifice its pedaling and climbing ability though, as Niner designs it with a steep 74-degree seat tube angle, which places you in an optimal pedaling position.
If you didn't know it by now, SIR is an acronym for "Steel is Real," so it only makes sense that the SIR 9 receives its construction from steel which yields that smooth, compliant ride over jarring sections of trail. So when picking which steel alloy to use, Niner went with the best, Reynolds 853, well renowned for its supple ride quality 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 hidden inner-plates stiffening and strengthening the frame's integrity—all without compromising the steel frame's compliance and supple feel.
This 2-star build packs a ton of value and comes with the massive gear range of SRAM's NX Eagle 1x12 drivetrain, and with its wide-ranging 11 to 50 tooth cassette eliminates the weight and complexity of a front derailleur with its wide gear range. It rolls on Niner Alloy wheels and Maxxis tires which we've had great luck with both in the dependability department.
- Niner's versatile steel hardtail with plus wheels
- Reynolds 853 steel adds compliance for smoother ride quality
- 27.5+ version provides greater speed and obstacle rollover
- Progressive geometry for lively handling and long-distance comfort
- Boost axle spacing accepts 29x2.5 and 27.5x3-inch tires
- 18 total mounts enhance carrying capacity for bikepacking
- SRAM NX Eagle drivetrain provides a wide gear range
- RockShox Judy fork provides 120mm of terrain-smoothing travel