New Niner S.I.R. 9 and IMBA Limited Edition Auction

29er Cross Country

At a time when carbon super bikes (including our own flagship models) dominate the stage, why would Niner shine a spotlight on the S.I.R. 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 loved as a kid? Why is steel just as relevant today as it was 50 years ago while other materials have come and gone?

Like other Ninerds, we ride and love steel bikes, as do bike connoisseurs around the world. But something about steel being equated with retro seems almost unfair. 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 S.I.R. 9 – All the fun, all the advantages, all the steel.

Highlights include:

  • Proprietary steel tubeset for ideal function and ride quality
  • Custom-bent double-butted Reynolds 853 DZB downtube
  • 44mm Reynolds 631 head tube allows use of tapered or 1-1/8″ forks
  • Niner Bio-Centric II bottom bracket system and removable downtube cable stops for clean singlespeed or geared setup
  • CYA compatible – run almost any contemporary crank style in geared set up
  • 142 x 12mm rear maxle
  • Post mount brake bosses between seatstay and chainstay
  • Investment cast stay bridges and dropouts
  • Tamale red or Arctic white
  • S.I.R. 9 frame MSRP $999.00

New Tubeset with Award Winning Niner Geometry

All steel is not created equal. The S.I.R. 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 new Reynolds 853 DZB (double zone butting) tubing. Developed for mountain bikes, and specifically 29ers, Reynolds 853 DZB offers two significant advantages:

Downtube Clearance – Fork/frame clearance for 29ers presents unique obstacles because of the relatively high headtube to bottom bracket 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. We worked with Reynolds to bend the 835 DZB downtube expressly for the S.I.R. 9 so the tube can attach lower on the headtube without interfering with the fork crown.

Increased Precision – A lower attachment point for the downtube improves front end rigidity. The Reynolds 853 DZB downtube further differentiates itself from others by incorporating two different butting profiles on the same tube – extra strength at the headtube to reduce torsional flex combined 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.

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 142 x 12mm axle, the rear end of the new S.I.R. 9 provides superior power transfer while preserving the smooth ride quality expected from a steel frame.

Complete the package with Niner’s hardtail geometry expertise and the result is a new frame that is sure to win as many rider’s choice awards and great reviews as has the original S.I.R. 9.

Oversized Headtube

The oversized headtube of the S.I.R. 9 allows the use of tapered fork steerer tubes that 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 S.I.R. 9 Lets you take full advantage of increased steering precision as you carve a corner and descend toward the finish.

Bio-Centric II Bottom Bracket System

The Niner Bio-Centric 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 tensioners cluttering your ride, no brake adjustments with gear changes.

Greater Range – The Bio-Centric II offsets the bottom bracket spindle 8.5mm from center, offering greater range of adjustment compared to a 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 bottom bracket shells that clamp an EBB can stretch or ovalize. The Bio-Centric 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, secure, quiet, easy to install and adjust, the Bio-Centric II will change your ideas about singlespeed drivetrain setup and maintenance.

Attention to Detail

While tubing upgrades are the focus of this new design, we haven’t forgotten the details. The new the S.I.R. 9 uses 142x12mm spacing with an included Maxle for added rear-end torsional stiffness, removable downtube cable guides, 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.

Availability + IMBA

The new S.I.R. 9 is available to order now and will begin shipping in 12 weeks. For those who want a S.I.R. 9 sooner, Niner will be auctioning six custom painted IMBA frames [SM (1) MD (2) LG (2) XL (1)] with matching RDO forks beginning Tuesday, June 19th – available worldwide. All proceeds from these auctions will go directly to IMBA.

“We believe that IMBA supports so many important things – trail access, maintenance and infrastructure that promotes life long commitments to health and exercise on the part of mtb riders. As a company that benefits from the health of cycling culture, it is only right that we contribute. This auction will be the only way to obtain one of the first six new S.I.R. 9 frames in the world.” Chris Sugai – Niner Bikes President

“This is the first time a company has dedicated an entire new bike launch to IMBA’s mission – we truly appreciate Niner’s above and beyond efforts on behalf of building and taking care of mountain bike trails. Niner is an extraordinary example of how a small company can make a big difference for the development of our sport.” Rich Cook – IMBA Development Director

For more information and to participate in the auction visit our Niner Facebook page

S.I.R. 9 Specifications & Compatibility

  • 73mm BB width (with EBB installed)
  • Bio-Centric EBB is compatible with external bearing cranksets only
  • 27.2mm seat post size, 400mm length recommended
  • 28.6mm front derailleur, high mount, bottom pull
  • 29.6mm seat collar size
  • Tapered headset with internal (ZS) top cup and 1.5” external bottom cup (included with frame). Cane Creek standard description: ZS44/28.6|EC44/40
  • Small has one bottle mount in the front triangle. Medium, large and XL have two bottle mounts inside the front triangle
  • Replaceable derailleur hanger or SS insert
  • 142 x 12mm Maxle rear spacing
  • Can fit up to a 2.4” tire (tire size varies by brand, some tires may not fit)
  • Compatible with standard 3x chainring systems
  • SRAM recommended 2x front chainring configs: 26/39 or lower
  • Shimano XT recommended 2x front chainring configs: 28/40 or lower
  • Shimano XTR double cranks have a non-standard chainline and are not recommended

* Geometry measurements are shown for 80mm and 100mm travel forks and include lower external headset cup
** Geometry measurements are shown for BB in line with seat tube, Bio-Centric EBB will change geometry depending on position

Geometry key:
(A) Effective Top Tube Length
(B) Seat Tube Length
(C) Chainstay Length
(D) Front Center
(E) Wheelbase
(F) BB Drop
(G) Head Tube Length
(H) Seat Tube Angle
(I) Head Tube Angle
(J) Standover
(K) Reach
(L) Stack

For more information visit

Photo Thumbnails (click to enlarge)


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