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FLUME FRAME

SPRING CLEANING SALE - 25% Off Full Price Bikes DISCOUNT APPLIED IN CART. Sale Ends 4/30!

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

$500.00 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

Customer Reviews

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Alan K.
Great frame at a great price!

I used the Flume frame as a base for a custom fat bike build. Fit and finish on the frame is very good. Tire clearance is also very good. Once built up, the bike handled very nicely and is super fun! It ended up being 32 lbs with a Rockshox Bluto and an AXS Reverb dropper, which is not too bad for a GX build.

User picture

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

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.

 


 

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 a 82mm rim / 29 x 2.25–3.0
Susp Fork Travel 100-120mm
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 Type Not Compatible
Bottom Bracket 100mm Threaded BSA 
Crankset (Max Ring) Chainline 76mm / 1x (34t)
Rear Brake (Rotor) 74mm post (160–180mm)
Rear Spacing 197 x 12mm thru-axle
Rear Axle ø12 x 229L, TP= 1.5, TL = 20
Derailleur Hanger Borealis Custom
Bottle Mount  SM : 2 (downtube) / MD, SM, XL: 3 (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

 

  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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