Borealis Flume Aluminum Fat Tire Bicycle

Borealis Flume: Built for Epic Adventures

Conquer mountains, snowfields, deserts, and everything in between on the Borealis Flume. Engineered around a lightweight 6000-series aluminum frame and a Borealis Carbon Rigid Fork, the Flume is designed to tackle any terrain with confidence. Choose between a SRAM NX Eagle or GX Eagle 12-speed drivetrain for precise shifting, while SRAM Level T brakes deliver all-weather stopping power. A carbon handlebar and seatpost keep the weight down without sacrificing strength, and Sun Ringle Mulefüt rims provide the durability you need for rugged rides.

With clearance for up to 26x5” or 27.5x4.5” tires and compatibility for 100–120mm of suspension travel, the Flume adapts to your style—whether you’re cruising winter singletrack, bikepacking across deserts, or hauling gear through alpine passes. Add in 2–3 bottle cage mounts, rear rack mounts, and Lizard Skins protectors, and you have a fat bike that’s truly expedition-ready.

Contact us today to build your custom Borealis Flume! Our 2025 Season pricing is now available, offering some of the best deals on the Borealis lineup.

Specifications

Drivetrain

• Eagle NX:
  • SRAM Eagle NX Crankset (175mm Alloy Arms)
  • RD ENX 1x12 Rear Derailleur
  • KMC X12 Chain
  • PG 1230 11-50 Cassette
  • SRAM Eagle NX Shifters
• Eagle GX:
  • SRAM Eagle GX Crankset (175mm Alloy Arms)
  • RD EGX 1x12 Rear Derailleur
  • KMC X12 Chain
  • XG 1275 10-50 Cassette
  • SRAM Eagle GX Shifters
• Chainring: SRAM 30T X-Sync
• Brakes: SRAM Level T

Frame & Fork

• Frame: Borealis Flume 6000-Series Aluminum
• Fork: Borealis Carbon Rigid Fork

Wheels

• Hubs: Borealis (Front 15×150, Rear 12×197)
• Rims: Sun Ringle Mulefut V2 (26" or 27.5")
• Spokes: Borealis Straight Gauge
• Nipples: Borealis Silver Brass
• Tires: Your Choice

Cockpit

• Handlebar: Borealis Carbon Bar (35mm)
• Stem: Borealis 50mm or 70mm
• Seatpost: Borealis Carbon Seatpost (31.6mm)
• Saddle: Borealis
• Grips: Borealis

Additional Features

• DT/CS Protector: Lizard Skins
• Mounts: 2–3 Bottle Cage Mounts, Rear Rack Mounts