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.

HIGHLIGHTS

• 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

SPECS

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

Frameset includes all of the above as well as:

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

All frames are covered by a 5 year warranty and crash replacement program.

RIDER HEIGHT RECOMMENDATIONS
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.

GEOMETRY & SIZING
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.

	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

 

So

Since 2013, Borealis has specialized in lightweight carbon fiber fat bikes. The tried and true, Carbon Fiber Crestone is our flagship model. Its frame geometry is optimized for riding in snow and sand with clearance for up to 5” wide tires. Paired with the most technically advanced components in the industry, the Crestone sets the standard for premium quality carbon fiber fat bikes.

HIGHLIGHTS:

• Frame geometry provides responsive and nimble handling for variable conditions in snow or sand.
• Internally routed cables.
• Tire clearance up to 26x5” and 27.5x4.5”.
• Compatibility for 100-120mm of suspension travel for more technical riding.
• Lightweight, durable carbon fiber frame comes with 2-3 bottle cage mounts and lizard skin protectors on both the down tube and drive-side chain stay.
• Available as frame only or as a frameset which includes a fork.

SPECS

Frame includes:

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

Frameset includes all of the above as well as:

• Complete headset and compression plug/ star nut
• Front axle

All frames are covered by a 5 year warranty and crash replacement program.

RIDER HEIGHT RECOMMENDATIONS
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.

GEOMETRY CHART
Stack and Reach are the fundamental fit elements, they are both measured relative to the bottom bracket. When choosing the Borealis that is right for you, it’s important to find a balance in these measurements to ensure the best performance.

	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	459 mm	459 mm	459 mm	459 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