Niner SIR 9 Hardtail



Niner's most versatile steel hardtail for dirt connoisseurs complete bike with 5 star bling kit.

Best paired with Niner's RDO frames, our "spare no expense" 5-Star Builds are filled with top of the line components for the cycling connoisseur or athlete who refuses to compromise.

SIR 9 Frame

  • Run singlespeed or geared
  • Custom drawn, 29er specific Reynolds 853 tubeset
  • Angled toptube to maximize standover clearance
  • S-bend chainstays
  • Niner's proven hardtail 29er geometry
  • Optimized for 80 to 100mm suspension forks
  • Disc brake only
  • Niner BioCentric EBB system for easy singlespeed set up
  • Breezer style forged vertical dropouts with 2 derailleur hanger options (singlespeed or geared)

5 Star Bling Kit

Fork Niner RDO Fork, 15MM
Wheels Niner XC Carbon, 15MM Front, 142 x 12MM Rear, Niner Graphic
Tyres Schwalbe Rapid Rob EVO TL 2.40/Racing Ralph EVO TL 2.25, Niner Graphic
Brakes & Rotors Shimano XTR M985, 180/160MM RT86 Ice Tech Rotors
Brake Levers Shimano XTR M988 Trail
Cassette Niner Cogalicious RDO
Chain SRAM PC 1
Crank Set SRAM XX1 GXP 32T
Bottom Bracket SRAM GXP
Saddle WTB Volt Team with NiCro Rails, Niner Graphic
Seat Post Niner RDO Seat Post, 400MM, Red Niner Graphic
Handle Bar Niner Flat Top RDO, 710MM, Red Niner Graphic
Stem Niner RDO Stem, Red Niner Graphic
Grips Niner Grrrips L/O


At a time when carbon super bikes (including our own flagship models) dominate the stage, why would Niner shine a spotlight on the SIR 9? Perhaps it’s better to ask “just what is it about steel bikes?” Why, when we get on a steel frame, are we instantly transported back to that first bike we had as a kid? Why is steel just as relevant today as it was 50 years ago while other materials have come and gone?

There wasn’t anything wrong with our SIR 9 – like other Ninerds we ride it and love it. But something about Steel being equated with Retro seemed almost unfair to such a great bike. There is simply no reason frames built with one of the best metals on the planet shouldn’t benefit from and take full advantage of cool technologies like updated headsets standards, tapered forks and through axles.

Introducing the new SIR 9 – all the fun, all the advantages, all the steel.

New Tubeset with Award Winning Niner Geometry

All steel is not created equal. The SIR 9 tubing is a custom-selected set that utilizes the best tube options for each application within the frame.

For the front triangle, we employ the new Reynolds 853 DZB (Double Zone Butting) tubing. Developed for mountain bikes, and specifically 29ers, Reynolds 853 DZB offers two significant advantages:

Downtube fork clearance in 29ers is tricky because of the relatively high HT-to-BB height. A straight downtube needs to be welded high on the back of the headtube to achieve fork clearance, often requiring either a gusset between the headtube and the downtube or a thicker heavier downtube to achieve desired strength. The Reynolds 853 DZB tube overcomes these limitations by incorporating two different butting profiles on the same downtube– extra strength at the headtube combines with a butting profile in the rest of the tube that maintains ride quality and avoids weight penalties – strong where we need it, compliant where we want it.

Another advantage and a significant first for this 853 DBZ tube is the proprietary bend. We worked with Reynolds to shape this tube for the SIR 9 so the tube can attach lower on the headtube, reducing front end torsional flex, increasing steering precision and adding strength.

For the stays, we incorporate steel custom bent in 3 dimensions – with investment cast bridges and dropouts – for ride quality and tire clearance. This shaping is proprietary to Niner and is not found on other steel mountain bikes. When combined with the new dropout system, provides superior power transfer while preserving the compliant ride quality you want in a steel frame.

When combined with Niner’s hardtail geometry expertise, the result is a new frame that is sure to win as many Rider’s Choice awards and great reviews as has the first SIR 9.

44MM Headtube

The new SIR 9 is now able to utilize tapered (or 1-1/8") steertube fork technology. The increased surface area of a tapered headtube allows for a larger downtube, increasing strength and rigidity at this critical intersection. Tapered fork steerer tubes measurably reduce fork deflection, which means your Niner tracks straight and true. The full spectrum of riders from XC racers to All Mountain shredders benefit from these features which is why we incorporate the technology in all our new frames. The SIR 9 lets you take full advantage of increased steering precision as you carve a corner and descend toward the finish.

The Niner BioCentric II makes adjustments easy across a wide range of gears and eliminates the need for adjustable dropouts, giving the cleanest possible solution for singlespeed use. No bolt on hubs, no chain tensioner cluttering your ride, no brake adjustments with gear changes.

Greater Range - The BioCentric II offsets the bottom bracket spindle 8.5mm from center, offering greater range of adjustment compared to a more traditional EBB setup. More offset is a boon when changing gears without having to change chain length and it allows riders to make more noticeable changes to frame geometry via BB position.

Reliable Function - Traditional EBB units are held in place with set screws that can become difficult to finely adjust over time, or expansion wedges that can deform the bottom bracket shell of the frame. Split BB shells that clamp an EBB can stretch or ovalize. The BioCentric II avoids these troubles by using two bolts to apply a clamping force on the outside edges of the BB shell, eliminating the possibility of ovalizing or indexing the shell itself. Field tested for over 18 months and 7000 miles, secure, quiet, easy to install and adjust, the BioCentric II will change your ideas about singlespeed drivetrain setup and maintenance.

Technical Information

While tubing upgrades are the focus of this new design, we haven’t forgotten the details. The new the SIR 9 uses 142x12 spacing with an included maxle for added rear-end torsional stiffness, post mount brake bosses between the chain and seatstay for braking precision, and, of course, the Niner headbadge and two great color options for that finishing touch.

  • Custom engineered steel tubeset for ideal function and ride quality
  • Custom bent double-butted Reynolds 853 DZB down tube
  • 44mm Reynolds 631 head tube allows use of tapered or 1-1/8” forks
  • Niner BioCentric II Bottom bracket system and removable down tube cable stops allows clean singlespeed or geared setup
  • 142x12 rear Maxle
  • Post mount brake bosses between seat stay and chainstay
  • Investment cast stay bridges and dropouts
  • Available in: Arctic White or Blaze Yellow

Geometry & Sizes

As a company dedicated to 29ers since our beginning, we at Niner are proud of our geometry expertise. As you will see in independent review after review, our bikes are held to the highest ride-quality standards, across our entire line up.

For riders who fall between sizes we recommend sizing down for a more maneuverable ride or sizing up for more stability.



Customer Reviews

Based on 1 review Write a review

Stage 1 Cycle Benefits

We go that bit further and test build all specialist bikes. With our attention to detail you will always get the right bike first time.