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ORDER NOW! Current lead time is 3-4 weeks for complete bikes.

0% APR up to 24 months with Affirm! Financing Options Available at Checkout.

$500.00 USD

Size Chart

bike size chart

Shipping and Returns

PO boxes not accepted.Shipping discounts or exclusions only apply within the lower 48 states of the US. Contact us if damage occurs during shipping. 

Borealis offers a 30-day money-back guarantee. If you are unsatisfied with your purchase for any reason, you can exchange your product or return it for a full refund minus any associated transaction fees and shipping costs. Customer is responsible for return shipping costs. Returned and exchanged items must be in sellable condition.


The Borealis Flume offers the best fat bike value on the market. This expedition-ready fatty mirrors the Crestone geometry, but does so in lightweight, 6000-series aluminum. Up mountains, down glaciers, and across deserts - the Flume is ready for action. There are all kinds of alloy fat bikes on the market, but none with the Flume’s purebred heritage and durability.


  • Traditional fat bike geometry is both responsive and nimble for variable conditions in snow or sand.
  • Standard features include: Eagle NX 12-Speed drivetrain, rigid carbon fork, carbon handlebars, carbon seat post and durable Sun-Ringle Mulefut rims.
  • Tire clearance up to 26x5” and 27.5x4.5”.
  • Compatibility for 100-120mm of suspension travel for increased comfort and control.
  • Lightweight, 6000-series aluminum frame comes with 3 bottle cage mounts, rear rack mounts on seat stays and Lizard Skin protectors on both the down tube and drive-side chain stay.
  • Available in two colorways
  • Reduced stand over height

Frames include:

  • Chainstay and seatstay protectors
  • Seatpost collar
  • Rear axle
  • Derailleur hanger

Frame with Fork includes all of the above as well as:

  • Fork of your choice
  • Complete headset assembly with compression plug / star nut
  • Front axle

All frames are covered by a LIFETIME warranty and crash replacement program.

  S M L XL EFFECTIVE TOP TUBE 585 mm 610 mm 630 mm 650 mm SEAT TUBE CENTER TO TOP 381 mm 432 mm 484 mm 534 mm HEAD TUBE 105 mm 120 mm 135 mm 150 mm SEAT TUBE ANGLE 73 deg 73 deg 73 deg 73 deg HEAD TUBE ANGLE 70 deg 70 deg 70 deg 70 deg STANDOVER HEIGHT Varies based on wheel and tire size CHAINSTAY 455 mm 455 mm 455 mm 455 mm BB DROP 60 mm 60 mm 60 mm 60 mm REACH 407 mm 423 mm 438 mm 451 mm STACK 597 mm 611 mm 625 mm 639 mm

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