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Niner Sir 9 Frame 2015

Item #: FR228A02
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Niner Sir 9 Frame 2015

Niner SIR 9 Frame

The Niner SIR 9 demonstrates steel is real! Steel bikes are as relevant today as they were 50 years ago. With that said, all steel is NOT created equal. The Niner SIR tubing is a custom selected set that utilizes the best tube options for each application within the frame. The front triangle is comprised of new Reynolds 853 DZB (Double Zone Butting) tubing. Developed for mountain bikes, more specifically 29ers, Reynolds 853 DZB offers two significant advantages. Historically downtube fork clearance on 29ers has been tricky because of the relatively high head tube 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 the desired strength. The Reynolds 853 DZB tube overcomes this limitation by incorporating two different butting profiles on the same downtube. The superior strength is combined with a butting profile in the rest of the tube that maintains ride quality, and keeps the weight down. Secondly, the 853 DBZ tube is the proprietary bend. Niner worked with Reynolds to shape the tube for the SIR 9 so the tube can attach lower on the headtube, which reduces front end torsional flex, and increases steering precision and adds strength.

Like the rest of Niner's bikes, the SIR 9 utilizes Niner's tried and true geometry. There are plenty of nifty features that you’ll find in the SIR 9. The Niner SIR 9 features the BioCentric bottom bracket system. The BioCentric makes adjustment easy across a wide range of gears and eliminates the need for adjustable dropouts. The BioCentric offsets the bottom bracket spindle 8.5mm from center, offering greater range of adjustment compared to a more traditional EBB setup. Not to mention, the ultra flashy head badge and dazzing paint is enough to make you swoon.

Niner SIR 9 Frame Features

  • 73mm BB width (with BioCentric installed)
  • BioCentric 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. Cane Creek standard description: ZS44/28.6 EC44/40
  • Small frame has one bottle mount inside the front triangle. Medium, large and XL have two bottle mounts inside the front triangle
  • Replaceable derailleur hanger or SS insert
  • 12 x 142mm 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 chainrings: 26/39T or lower
  • SRAM XX1 recommended max chainring: 36T with BioCentric forward. Q-Factor: 168mm
  • SHIMANO XT recommended 2x chainrings: 28/40T or lower
  • SHIMANO XTR 2x is not recommended. Both versions (40t/48.8mm chain line and 38t/46.6mm chain line) position the large chainring in a way that it may contact the frame.
Geometry (80mm fork)
Size Small Medium Large Extra Large
Effective Top Tube Length 589mm 605mm 624mm 643mm
Seat Tube Length 393mm 419mm 483mm 546mm
Head Tube Length 100mm 110mm 125mm 145mm
Head Angle 70.8° 71.3° 71.3° 71.3°
Seat Angle 73.3° 73.3° 73.3° 73.3°
BB Drop 56mm 56mm 56mm 56mm
Front Center 646mm 658mm 678mm 696mm
Wheel Base 1078mm 1089mm 1109mm 1128mm
Chain Stay Length 440mm 440mm 440mm 440mm
Reach 405mm 418mm 433mm 446mm
Stack 614mm 622mm 645mm 659mm
Standover Height 711mm 732mm 785mm 836mm

Geometry (100mm fork)
Size Small Medium Large Extra Large
Effective Top Tube Length 592mm 609mm 628mm 647mm
Seat Tube Length 393mm 419mm 483mm 546mm
Head Tube Length 100mm 110mm 125mm 145mm
Head Angle 69.8° 70.3° 70.3° 70.3°
Seat Angle 72.3° 72.3° 72.3° 72.3°
BB Drop 49mm 49mm 49mm 49mm
Front Center 651mm 664mm 684mm 701mm
Wheel Base 1085mm 1096mm 1115mm 1135mm
Chain Stay Length 440mm 440mm 440mm 440mm
Reach 395mm 409mm 423mm 436mm
Stack 620mm 637mm 652mm 671mm
Standover Height 716mm 736mm 790mm 842mm
4.8 / 5.0
5 Reviews
5 Stars
4 Stars
3 Stars
2 Stars
1 Stars
Good Frame
Great Frame. I wanted a steel frame that was versatile, this one seems like the best option. Fun to ride, good with steep trails and single track. I ride it with RDO carbon fork, very fun.

Some notes on components and set up. Be real sure you want to ride SS before you buy any frame with the Eccentric Bottom Bracket; it may not be worth the trouble if you don't ride it SS often. Also, I don't recommend any 30 mm spindle bottom bracket with the EBB sleeve; too large outside diameter to set while mounted. I ride the Race Face Cinch cranks and there is no way to do this set up as SS and get the right torque on the EBB. In fact, don't do any crank that disconnects on the drive side.

Lastly, I was able to resolve, but the QC on the rear axle threads was poor. They simply didn't align on both sides of the frame. Niner customer service was useless. I changed out the set screw that comes with the hanger and got it to work but I expected better QC from Niner.

PROS: Attractive Design, Fun, Versatile, Durable

CONS: Limited Compatibility, Quality Control
November 29, 2015
Seattle WA
Steel Is Real
This bike is incredible. You will not understand until you have rode one. Steel is most definitely the real deal. For most of us, who are not at the top of our class sponsored athletes, we ride for the pleasure of riding. This is the bike that helps you remember why you mountain bike!

PROS: Steel Frame, Durable, Attractive Design, Lightweight, Did I Mention The Steel, Steel

CONS: Heavier Than Carbon
November 11, 2014
Riverside, CA
Excellent steel frame
Arrived as expected.
August 22, 2016
Fort Mill, SC
A classic that can last decades
The SIR9 is a very high quality steel frame with an extremely smooth finish and clean welds. The rear spacing does clear Maxxis 2.35 Ikon tires mounted on Flow MK3 rims.

To fully enjoy this compliant frame, use Niner's RDO carbon seatpost and RDO handelbars. Combined with high-volume tubeless tires like the Ikons, you will achieve that magic carpet ride which only steel can deliver!
December 11, 2016
1 year ago
Best hardtail in 30 years.
Been riding Mtn bikes since 1986, all hardtails, mostly steel, a few Ti, and the SIR 9 is the nicest riding frame I've had the pleasure to build and ride.
October 21, 2016
Glenville, NC

Q & A

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Browse 2 questions Browse 2 questions
Does this frame come with the Bio Centric II BB, headset and rear thru axle?
Brad on May 16, 2016
2.4" 29er tires for trail riding is one thing, but what if you want to go plus size some days? Would it be possible, advisable to use wider 27.5" rims with 3" tires on the bike, and ride it through more bumpy terrain?

I ride 29er rigid single 90% of my rides, and occasionally, I go somewhere with rocks on top of rocks, and 3" tires might be all the suspension I need. So, just a change of wheels, and away I go.

Just not sure if this makes sense, or it's a bad idea in my head.
trailrider29 on Jul 28, 2016

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Get free Standard Shipping with your $50 purchase today! Just choose Standard Shipping during checkout.

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