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Flume Ultimate Aluminum Fat Bike

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

$2,619.00 USD

Size Chart

bike size chart

Shipping and Returns

Borealis does not accept shipments to PO boxes, and additional charges may apply for deliveries to Alaska and Hawaii. We offer flat rate shipping on all products through the most economical FedEx option.

Bikes, frames, and wheelsets typically ship via Ground, while small parts are shipped using 2-Day Express. Please contact us if any damage occurs during shipping.

Borealis provides a 30-day money-back guarantee. If you're not satisfied with your purchase, you can exchange the product or return it for a full refund, minus any transaction fees and shipping costs. Return shipping is the customer’s responsibility, and all returned or exchanged items must be in sellable condition.

LIMITED LIFETIME WARRANTY

LIMITED LIFETIME WARRANTY ON BICYCLE FRAMES & FORKS

FOR PURCHASES MADE ON OR AFTER JANUARY 1, 2023:

Original Owner
BOREALIS offers a LIMITED LIFETIME warranty to the original owner of each new BOREALIS bicycle, fork or frameset that the bicycle frame, fork or frameset when new is free of defective materials and workmanship.

Normal Conditions
The limited warranty is conditioned upon the bicycle being operated under normal conditions and use, and properly maintained.

Limitations
This limited warranty does not apply to paint/finish or components attached to the bicycle/fork/frameset such as rims, drive train, brakes, seat post, handlebar and stem, or any suspension related parts or components.

Paint/finish, components attached to the bicycle/frameset such as rims, drive train, brakes, seat post, handlebar and stem, or any suspension-related parts or components are covered under the limited one (1) year warranty.

Load Weight
The total cargo load for BOREALIS frames and forks is 300 pounds. The total cargo load includes the rider and any associated gear warn by the rider or attached to the frame or fork.


PURCHASES MADE BEFORE JANUARY 1, 2023 HAVE A 5-YEAR WARRANTY WITH THE SAME LIMITATIONS.


LIMITED ONE (1) YEAR WARRANTY ON COMPLETE BICYCLE
Subject to the following limitations, terms and conditions, BOREALIS warrants to the original owner of each new BOREALIS bicycle that this bicycle, when new, is free of defective materials and workmanship. This warranty shall expire one (1) year from the date of the original purchase from an authorized BOREALIS dealer and is conditioned upon the bicycle being operated under normal conditions and use, and properly maintained. This warranty is void if the bicycle was not purchased new or not properly assembled by an authorized BOREALIS dealer.
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Customer Reviews

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G
GREG CARLSON
Flume Ulimate

AWESOME RIDE. Easy to assemble. Great support staff.

The Flume Ultimate is specifically configured for riders looking for a capable, single-track-ready fat bike. This bike has all the features and capability for steep climbs and descents anywhere, anytime. Standard features include Manitou Mastodon Pro EXT 120mm Suspension Fork, SRAM Eagle GX 12-speed drivetrain, G2 RS 4-piston brakes, SunRingle Mulefut 27.5" wheels, Maxxis Minion FBF/FBR 3.8" Tires.  

 

 

Frame Flume (Aluminum)
Fork Manitou Mastodon Pro EXT 120mm or RockShox Bluto RL 100mm (based on supply)
Bottom Bracket SRAM DUB Threaded 100mm
Crankset SRAM Eagle GX Alloy 175mm w/ SRAM X-SYNC 30T
Rear Derailleur SRAM Eagle GX 12-Speed
Chain SRAM EAGLE GX
Cassette SRAM XG-1275 10-52T
Shifter SRAM Eagle GX 12-Speed
Brakes SRAM G2 RS 4-Piston Hyrdraulic with SRAM Centerline 160mm Rotors
Headset FSA
Hubs Borealis GEN 4 Black 15x150 Front / 12x197 Rear
Rims Sun Ringle Mulefut V2 27.5x65
Spokes Borealis Straight Gauge
Nipples Borealis Silver Brass
Tires Maxxis Minion FBF/FBR 27.5x3.8
Bar RaceFace NEXT SL 740x10mm OR Borealis Carbon (based on supply)
Stem Borealis 50mm x 35mm
Post KS Lev Integra w/ Southpaw Lever 125mm (SM, MD) or 150mm (LG, XL) travel
Saddle Borealis
Grips Borealis
DT/CS Protector Lizard Skins
Estimated Weight Size Large 33 pounds



Wheel / Tire Size 26 x 3.8–5.0" on up to a 100mm rim / 27.5 x 2.8-4.5 on up to an 82mm rim / 29 x 2.25–3.0
Max Fork Travel 120mm
Fork Offset 51mm
Headset-Upper IS41
Headset-Lower IS52
Seatpost ø31.6mm
Seat Collar ø34.9mm
Dropper Compatible Internal - 125mm for SM & MD / 150mm for LG & XL
Front Derailleur  Yes
Bottom Bracket 100mm Threaded BSA
Crankset (Max Ring) Chainline 76.5mm / 1x (34t)
Rear Brake (Rotor) 74mm post (160mm)
Rear Spacing 197 x 12mm thru-axle
Rear Axle ø12 x 229L, TP= 1.5, TL = 20
Derailleur Hanger Borealis Flume
Bottle Mount  Small & Medium: 1 (downtube) / Large & XL: 2 (downtube & seatube)
Rear Rack Reccomendation Old Man Mountain Divide Fat 
Rear Rack Mounts, Upper Yes
Axle to Crown 487mm
Steerer Tube Size 28.6mm
Steerer Style Tapered
Crown Seat Diameter 40mm

 

 

 

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
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

 

 

ASSEMBLY

There is some assembly required upon receipt. Your bike will be completely assembled and tuned by Borealis, then partially disassembled for shipment. The remaining assembly will require installation of the rear derailleur, chain, fork, seat post, wheels, and handlebars. A multi-tool will be included with your order that has all tools necessary to assemble the bike, with the exception of a torque wrench. If you are not familiar with this level of assembly, we recommend having your local bike shop complete the assembly. Below is a video showing the remaining assembly once you receive the bike. Tires will be set up with tubes. Tubeless rim tape and valves are included on the side.

Assembly Video 

Download Owner's Manual

Check out our FAQ page for more information.