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Niner S.I.R. 9 Mountain Bike Frame

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$999.00

Item # NNR0030

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Item # NNR0030

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Yes, S.I.R.

The award for best ride quality has always gone to steel. That’s where the Niner S.I.R. 9 frame shines. The S.I.R. 9 isn’t just steel, it’s Reynolds 853—one of the best, most respected steel alloys for bicycle frame-building. Because of this, the S.I.R. 9 has that legendary ride quality that everyone else is chasing. Sure, it may be a little heavier than your dentist’s carbon fiber frame, which costs more than your car, but it rides better. And, while we agree that the S.I.R. 9 is a little bit old-school, it isn’t behind the times. You get 142mm rear spacing, a post-mount rear caliper, and the option to run just about any drivetrain configuration out there, from singlespeed to 33-speed.

The secret behind all this drivetrain diversity is the eccentric bottom bracket. The EBB makes setup simple, unlike individual adjustable dropouts.

If you plan on going the geared route, Niner recommends doubles not exceeding 26/39 chainrings for SRAM, and 28/40 for Shimano. However, a standard triple will pose no problems. The rear triangle will accommodate a 2.4in tire, and you can run a 160mm rear rotor. You’ll need a bottom pull, high mount front derailleur with a 28.6mm clamp. The S.I.R. 9 uses a 27.2mm seatpost, a 73mm BB (only external style bottom brackets work with the EBB), and a 44mm tapered headset. The maximum chainring size varies depending on the position of the BioCentric EBB insert. At the most rearward position, the Niner recommends running no larger than a 30t chainring, and when in the forward position, it will accept a 36t ring. It comes with a Maxle rear axle.

  • Reynolds 853 steel frameset
  • 142mm rear spacing
  • Eccentric bottom bracket

Tech Specs

Frame Material:
steel
Suspension:
hardtail
Head Tube Diameter:
[upper cup] ZS44/28.6, [lower cup] EC44/40
Headset Included:
yes
Bottom Bracket Type:
Niner Bio-Centric EBB
Cable Routing:
external
Front Derailleur Mount:
28.6mm clamp-on, high-clamp
Derailleur Pull:
bottom
Compatible Components:
Shimano, SRAM
Seatpost Diameter:
27.2 mm
Recommended Use:
cross country
Manufacturer Warranty:
2 years on frame

Geometry chart

Niner Bikes

Geometry Chart

 

S.I.R. 9
80mm Fork
 

Seat Tube

(c-t)

Effective Top Tube

(eTT)

Stack

(S)

Reach

(R)

Standover

Head Tube

(HT)

Head Tube Angle

(HTo)

Seat Tube Angle

(STo)

Bottom Bracket Drop

(BBD)

Chainstay

(CS)

Wheelbase
S 15.5in 23.2in 24.2in 15.9in 28.0in 3.9in 70.8o 73.3o 2.2in 17.3in 42.4in
M 16.5in 23.8in 24.5in 16.5in 28.8in 4.3in 71.3o 73.3o 2.2in
17.3in 42.9in
L 19.0in 24.6in 25.4in 17.0in 30.9in 4.9in 71.3o 73.3o 2.2in 17.3in 43.7in
XL 21.5in 25.3in 25.9in 17.6in 32.9in 5.7in 71.3o 73.3o 2.2in 17.3in 44.4in
100mm Fork
 

Seat Tube

(c-t)

Effective Top Tube

(eTT)

Stack

(S)

Reach

(R)

Standover

Head Tube

(HT)

Head Tube Angle

(HTo)

Seat Tube Angle

(STo)

Bottom Bracket Drop

(BBD)

Chainstay

(CS)

Wheelbase
S 15.5in 23.3in 24.4in 15.6in 28.2in 3.9in 69.8o 72.3o 1.9in 17.3in 42.7in
M 16.5in 24.0in 25.1in 16.1in 29.0in 4.3in 70.3o 72.3o 1.9in 17.3in 43.1in
L 19.0in 24.7in 25.7in 16.7in 31.1in 4.9in 70.3o 72.3o 1.9in 17.3in 43.9in
XL 21.5in 25.5in 26.4in 17.2in 33.1in 5.7in 70.3o 72.3o 1.9in 17.3in 44.7in

Niner S.I.R. 9 Geo

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Here's what others have to say...

WIll my S Roval 142 wheel set fit? It uses a Syntace axle not a Shimano. Thanks.

Responded on

If the rear end is a 12x142 it will fit. You will just need to use the axle that comes with the Niner frame as the treads in the frame are different.

4 5

Modern-technology be damned, sometimes

  • Gender: Male
  • Familiarity: I've used it several times

I've loved the idea of a steel bike since the beginning. There are (literally) millions of threads and blog postings talking about why steel is still a relevant (and good) material to use for bike frames, so I won't delve into all of that. I came off a Pivot LES, and a Highball Carbon before that, so I've had my fair share of creme de la creme carbon hardtails. To feed my never-ending lust for steel, I decided to give the new SIR9 a try. The stereotypes are true - it's pretty heavy, it is really smooth (smoother in the rear than either of my previous carbon hardtails), and is relatively heavy (yep, it's like a pound or two heavier than my other frames were). But for me, especially this time of year, I don't really care all that much. I don't have to worry about damaging the frame (I suppose I need to be conscious of rusting, but FrameSaver should take care of that), and it's pretty inexpensive. And it's fun, and different. And it's easy to make it single speed or geared. I dig it - when spring rolls around and I go back to slogging up thousands of feet of vertical, my tune my change a bit, but as a cool all-around hardtail (especially for midwest riding), this thing is rad.

Modern-technology be damned, sometimes