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.
Work With Us On a Custom Build
If you’re thinking about a custom gravel, MTB, or road build, we can help you spec it out and build it the way you want.