Review: Niner SIR 9 – A Truly Do Everything Frame

In early 2017, the SIR 9 had vanished from Niner’s website, shocking and confusing more than a few fans of this steel-framed classic. It wasn’t until June that Niner officially released its newly revamped SIR 9, and with the dust settled, it was time for Dirt Rag to see how this classic has evolved.

Brad Cole, Niner’s marketing manager, states, “The new SIR 9 is a fusion of the ROS 9 geometry, the versatility of the ROS 9 Plus and heritage of the SIR 9.” It’s built around a 120 mm fork and offers modern trail geometry, mounting points out the wazoo, and air-hardened Reynolds 853 steel tubing. When asked about the primary market for the new SIR, Cole says, “We call the SIR 9 our “do it most” bike. The ideal rider is someone looking for the playful and confidence-inspiring geometry characteristics of a modern trail bike in a hardtail package.”

Steel is Real: Niner’s SIR 9, the “Do it most bike”

For our review, we requested the 2-Star 27plus build, which comes stock with a Stan’s Baron MK3 wheelset and Maxxis Rekon 2.8 tires, RockShox Reba 120 mm fork, and Shimano SLX 1×11 groupset. For 2018, the 2-Star build kit is $100 less and comes equipped with a Fox 34 Rhythm, SRAM Guide R brakes, and an SRAM GX 12-speed drivetrain. Not too shabby for a bike just over $3,000.

The Ride

As much as I love the geometry updates that Niner made to the SIR 9, the ride quality was not as svelte as I anticipated. Both the front and rear end of the bike felt overly stiff, even harsh. After various experiments with bar, stem, and grip combinations, I found that the front end stiffness was largely due to the 35 mm diameter stem and aluminum bar. Once I switched to a carbon bar and 31.8 mm diameter stem, the front end became more compliant and responsive.

To the rear, the newly designed three-piece chainstay yoke features a horizontal plate to handle the more progressive trail geometry and accommodate up to 3-inch 27plus tires. Besides a heavy dose of stiffness, the yoke also proved to be problematic when it came time to run the SIR 9 as a 29er. The cornering lugs of a handful of common 29×2.3 trail tires mounted on three separate rims with 26, 29, and 30 mm internal widths rubbed the inside of the yoke. A WTB Breakout 2.3 on a Flow MK3 rim jams against the top of the yoke.

We sent the bike back, and Niner determined that the stays are 3 mm shorter than spec. Niner claimed that the bike fit a Minion DHR II on an Enve M70 rim. If consumers encountered this issue, Niner “would work with them on a warranty resolution.”

With the 27plus tires back on and a 31.8 mm stem/bar combo, the more I rode the bike, the more I started to look past its faults. The updated geometry was on point for both 27plus and (skinny) 29er wheels. One of the biggest complaints I’ve continuously had with 27plus wheels on 29er frames is the lowered bottom bracket height, but the SIR 9 finds a good middle ground. There is no extra thought required to avoid pedal strikes; the height of the bottom bracket simply never crossed my mind while riding, and I appreciated that, a lot.


Aside from the yoke snafu for 29er trail tires and ditching the 35 mm stem/bar combo, the new SIR 9, as a 27plus bike, is a versatile, capable ride. Assuming that our review bike’s lack of 29er tire clearance is a one-off, the SIR 9 just may be the perfect bike for someone who falls in the Clydesdale class. The majority of mass-produced steel hardtails would likely feel like a wet noodle under a heavier rider; this bike’s stiffness might be just the ticket.

Riders looking for a bike more akin to the cross-country ride of the previous-generation SIR 9 should keep looking. This is not the hardtail you are looking for.


  • Reach: 17.5”
  • Stack: 24.9”
  • Top Tube: 24.7”
  • Head Tube: 68 degrees
  • Seat Tube: 74 degrees
  • BB Height: 12.5”
  • Chainstays: 16.9”
  • Weight: 29.7 lbs. without pedals
  • Sizes: S, M, L (tested), XL
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Review: Niner SIR 9 - A Truly Do Everything Frame — Bike Hacks