Instock, built and ready to go
With premium frame quality and only the best components, the Borealis Flume offers the best 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”
- 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.
Eagle 12 speed Flume Specs (1×12)
|.||Eagle NX||Eagle GX||Eagle XO||Eagle XX|
|Crankset||SRAM Eagle NX||SRAM Eagle GX||SRAM Eagle XO||SRAM Eagle XX|
|Crank Arms||175mm Alloy||175 Alloy||175mm Carbon||175 Carbon|
|Rear Derailleur||RD ENX 1 x 12||RD EGX 1 x 12||RD EXO 1 x 12||RD EXX 1 x 12|
|Chain||KMC X12||KMC X12||KMC X12||SRAM X12 Gold|
|Cassette||PG 1230 11-50||XG 1275 10-50||XG 1295 10-50||XG 1299 10-50 Gold|
|Shifters||SRAM ENX||SRAM EGX||SRAM EXO||SRAM EXX|
|Brakes||SRAM - Select||SRAM - Select||SRAM - Select||SRAM - Select|
|Chain Ring||30 Tooth|
|Fork||Borealis Carbon Rigid Fork or RL Bluto, Mastodon Pro Ext.|
|Hubs||Borealis: Front 15×150 Rear 12×197|
|Nipples||Wheelsmith Silver Brass|
|Bar||Borealis Carbon Bar 35mm|
|Stem||Borealis 50mm or 70mm|
|Post||Borealis Carbon Seatpost|
|Grips||Ergon GA30 or Ergon GP 10L|
|Bottom Bracket||SRAM DUB 100mm|
|DT/CS Protector||Lizard Skins|
|Weight||See weight calculator for exact weight.|
Based on our research, riders at the heights below will usually take the corresponding frame size. If you’re at a transitional height that spans two sizes, look at the geometry chart to get the Stack and Reach you like based on other bikes you are comfortable.
Borealis offers four frame designs with unique fit and geometry to suit your every Fat Bike need. Begin by taking a rough size approximation on the chart below that is based on height, then select the corresponding bike with your fit needs by using the geometry chart further below. We recommend a similar fit to you mountain bike, so grab a measuring tape and dial it in.
|EFFECTIVE TOP TUBE||23.02 in||24.02 in||24.8 in||25.59 in||585 mm||610 mm||630 mm||650 mm|
|SEAT TUBE CENTER TO TOP||15 in||17.01 in||19.06 in||21.02 in||381 mm||432 mm||484 mm||534 mm|
|HEAD TUBE||4.13 in||4.72 in||5.31 in||5.91 in||105 mm||120 mm||135 mm||150 mm|
|SEAT TUBE ANGLE||73 deg||73 deg||73 deg||73 deg||73 deg||73 deg||73 deg||73 deg|
|HEAD TUBE ANGLE||70 deg||70 deg||70 deg||70 deg||70 deg||70 deg||70 deg||70 deg|
|STANDOVER HEIGHT||Due to various rim and tire options stand over is not identified.|
|CHAINSTAY||17.91 in||17.91 in||17.91 in||17.91 in||455 mm||455 mm||455 mm||455 mm|
|BB DROP||2.36 in||2.36 in||2.36 in||2.36 in||60 mm||60 mm||60 mm||60 mm|
|REACH||16.04 in||16.65 in||17.22 in||17.76 in||407.3 mm||423 mm||437.5 mm||451.2 mm|
|STACK||23.50 in||24.05 in||24.61 in||25.16 in||597 mm||610.9 mm||625 mm||639.1 mm|
Getting FAT | A Fat Biking Story
6 years ago, Dave Ochs, John Norton, and Steve Kaczmarek helped found the Borealis Fatbike World Championships. Today, it's in its 5th year with over 750 riders having participated in the elite division and over 1,400 competitors in all of the various races during worlds. This is that story.