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Build Overview
This is one of our custom-built 3-Star Niner AIR 9s — the aluminum version. Niner doesn’t offer this configuration, but we ended up with extra 3-Star parts kits from AIR 9 RDO carbon builds and realized we could create some really strong budget-friendly hardtails by pairing those kits with the AIR 9 alloy frame.
For the money, this setup is tough to beat. You get a quality fork, a proven drivetrain, and the ride characteristics of the AIR 9 platform without stepping into carbon pricing. We have experience riding the AIR 9 RDO builds ourselves, so it was fun putting together an aluminum version using nearly the same components.
It’s a simple, durable, and fast build that works well for local singletrack or high school XC racing, and it hits a great price point under $2,000.
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Full Build Specs
- Frame: Niner AIR 9 (aluminum)
- Wheelset: Stan’s Arch S1
- Front Tire: Schwalbe Racing Ray 2.35
- Rear Tire: Schwalbe Racing Ralph 2.35
- Drivetrain: SRAM GX Eagle (12-speed)
- Crankset: Truvativ Descendant
- Cassette: GX Eagle
- Rear Derailleur: GX Eagle
- Shifter: GX Eagle
- Chain: GX Eagle
- Fork: Fox Factory 32 Step-Cast (remote lockout)
- Brakes: SRAM G2 R (4-piston)
- Rotors: SRAM Centerline — 180mm front, 160mm rear
- Handlebar: Niner XC Carbon Bar
- Stem: Standard aluminum stem
- Seatpost: Niner aluminum seatpost
- Saddle: Standard saddle (varies by test-fit)
Build Notes
This AIR 9 frame is the aluminum version—simply “AIR 9.” The carbon frame is the “AIR 9 RDO.” This alloy frame runs fully external routing for the shifter and brake lines, which is actually nice for maintenance and setup. It’s boosted front and rear, with thru-axles and a straightforward design that’s easy to work on.
The wheels are Stan’s Arch S1 rims. These typically show up on OEM-spec Niner bikes, and we had them on hand from previous carbon AIR 9 RDO builds. The tire setup is a Racing Ray/Racing Ralph combo in 2.35, a fast and predictable XC pairing we’ve used a lot. Once you get used to how these tires bite in corners, they’re a great race or trail option.
The drivetrain is a standard GX Eagle setup with a Truvativ Descendant crank. This is the same 3-Star kit that ships with carbon AIR 9 RDO builds, and we just carried it over to the alloy frames. GX Eagle performs well, is cost-effective, and is easy to maintain.
For brakes, it’s SRAM G2 R four-piston calipers. I’ve become a big fan of four-piston brakes even on XC bikes. The extra braking power is noticeable, and the G2 line has a really nice lever feel. Paired with 180/160 Centerline rotors, the balance feels right.
The cockpit includes the Niner XC carbon handlebar and a standard stem. We left the stock aluminum seatpost instead of adding a dropper because droppers can swing the price by a couple hundred dollars. Everyone has different dropper preferences at this budget, so this keeps the build flexible.
The fork is a Fox Factory Step-Cast 32 with a remote lockout. Personally, I don’t use remote lockouts, but some riders love them. Set the air pressure right and the damping works well regardless.
Who is this bike for? A few groups: riders who want high-quality components but don’t need a carbon frame, local singletrack riders looking for a fast XC platform, and high school racers who want a competitive bike without spending carbon money. At under $2,000, it’s a strong value.
Our goal with these custom AIR 9 builds was simple—build the best hardtail we can for the money using the parts kits we already had. And in this case, it came together really well.
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