Mountain Bike Action Bike Test: Niner Sir 9 2.0 Trail Bike


The Niner Y.A.Y.W.D. (You Are What You Drink) Top Cap allows a rider to customize their ride by snapping their favorite beverage cap over the built-in lip.


The latest Niner SIR 9 2.0 build was designed to maintain the real factor of the previous version by continuing to use high-end Reynolds 853 steel tubing. To no one’s surprise, the steel frame has been updated with a more modern trail geometry and today’s industry standards.

The longer wheelbase and slacked-out, 68-degree head tube contribute to the stability of the bike’s design, while the steep 74-degree seat tube angle places a rider over the bottom bracket for a better power position over the pedals. A notable feature is the BioCentric bottom bracket system that gives you the option to run a single-speed or geared drivetrain. Given the versatility of steel, the SIR 9 2.0 has been outfitted with 18 mounting points for all your adventure gear needs. The remaining amenities include internal routing for a dropper post, clearance for 29 × 2.4-inch or 27.5+ × 3.0-inch tires, a tapered head tube, a 12mm rear thru-axle and Boost rear-hub spacing.

The frame’s chainstay and seat-stay yokes are designed to accommodate either 29″ or 27.5+, with a decent amount of mud clearance to spare.


Niner currently offers four different builds of the SIR 9 2.0. If you like to build up your own frame and pick your own components for installation, they do offer a frame-only option for $1,200. Niner rates its different builds with a star system. The entry 2-Star build comes with SRAM SX Eagle and a Marzocchi fork priced at $2,500. The 3- and 4-Star builds are furnished with Shimano)(1- components and Fox suspension forks, and range from $4,050 to $4,900 in price. We were fortunate to put what was essentially the 5-Star SRAM X01 build through our testing; however, our build was slightly modified compared to the 5-Star build on Niner’s site.

Defiant Packs teamed up with Niner to create a custom frame bag that is ideal for loading up and heading out on a multi-day bike packing trip.

If you pop over to their website, it will say that the 5-Star build comes with a carbon wheelset and a 120mm fork. Our test bike was fit with Stan’s Flow 51 alloy wheelset and a 130mm fork instead, but we’ll get into more details on how those components performed later. Handling is achieved with a short Race Face stem clamped to a 720mm carbon Next R handlebar. Clamped to the bars are the SRAM G2 RSC brakes to halt this steel beast. Setting this rig on the dirt are Manis tires with a 29 × 2.5-inch in the front and a 29 × 2.4-inch in the rear.

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