Niner

SIR 9 Mountain Bike Frame

The Niner SIR 9 Mountain Bike Frame is one of the most versatile hardtails on the market thanks to its supple Reynolds 853 steel construction paired with modernized trail geometry, the ability to run 29-inch or 27.5+ wheels, and 18 mounting points for bikepacking adventures. Whether you're seeking a steel hardtail for spirited rides through the local forest or you're looking for a dependable pack mule for long-distance adventures, the SIR 9 satisfies your itch for exploration with its simplicity, strength, and unmatched versatility. The customization doesn't stop there, with the SIR 9 accommodating both geared and singlespeed drivetrains, although singlespeeds require Niner's Biocentric 30 (not included).

Seeing that the bike industry is ever-evolving, it makes perfect sense that Niner designed the latest SIR 9 with their [R]evolution trail geometry, which makes the bike longer in the top tube and shorter in the chainstays. This redesign gives the SIR 9 a lively personality that's quick to turn through tight switchbacks and sweeping berms, as well as making it roomier in the cockpit, so you're well-balanced and comfortable across long distances. The longer wheelbase tracks confidently when you open it up at higher speeds for added composure without it ever feeling twitchy or unnerving when pushed to the limit.

Delving into the frame construction, you'll love the smooth, supple feel of SIR 9's Reynolds 853 steel, especially when you're rallying it over bumpy sections of rocks and diving into swooping corners where steel brings extra compliance to the terrain. 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 regular stresses of trail riding. Inside the frame, Niner places a hidden inner-plate that stiffens and strengthens its integrity—all without compromising the steel frame's compliance and supple feel.

And because of its popularity in the bikepacking realm, the SIR 9 is loaded with a myriad of mounts for saddle bags, fenders, accessory carriers, and water bottles. You'll find 18 mounting points in total, with two inner-triangle mounts for water bottles, another pair of bottle mounts under the down tube, fender mounts conveniently situated on the rear stays, two bosses for a top tube bag, and another two bosses underneath the top tube for a bolt-on frame pack. In fact, there are so many mounts, we probably forgot to mention a few possible configurations, but we're sure you'll find a handy way to make use of them!