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When your 2-wheeled adventure is all about the traction, hop aboard the Diamondback El Oso Uno fat bike and let its massive tires carry you over rocks, sand and snow with ease.

  • Features

    • 73mm wide rims and 32-hole disc hubs take the hits and float over just about anything in your path
    • 170mm rear hub spacing will fit tire sizes up to 26 x 5 in.
    • Steel frame is solid, durable and soaks up bounce
    • Custom rigid steel fork is disc-compatible
    • Shimano Acera 2x9 drivetrain provides precise shifting and low gearing
    • Tektro Novela mechanical disc brakes bring you to a tidy stop
    • Specs are subject to change


    Free Adjustment Period:
    New bikes go through a normal break-in period, after which they should be readjusted. All bicycles sold at REI include free adjustments for one year after purchase date—as many times as you need. Included: derailleur and brake adjustments, lateral wheel truing, hub and headset bearing adjustments, tire inflation and chain lubrication. Not included: replacement or installation of new components or accessories, any other services. Call your local REI Co-op Bike Shop for more information.
    View all Diamondback Rigid Mountain Bikes
  • Technical Specs

    Best Use

    Mountain Biking

    Mountain Bike Style


    Bike Frame Material






    Bike Suspension

    No Suspension


    SR Suntour XCM, 36/22T

    Bottom Bracket

    Sealed cartridge


    Shimano Acera M3000

    Front Derailleur

    Shimano MT400

    Rear Derailleur

    Shimano Acera M3000

    Rear Cogs

    Shimano HG200, 11-36T, 9-speed

    Number of Gears

    18 gear(s)

    Brake Type

    Mechanical Disc Brake


    Tektro Novela

    Brake Levers

    Tektro 2-finger alloy


    14g stainless-steel

    Front Hub

    Alloy, 32h

    Rear Hub

    Alloy, 32h

    Wheel Size

    26 inches


    Chaoyang Cruiser

    Tire Width

    4.0 inches

    Handlebar Shape

    Riser Bar




    DB Race M-series

    Seat Post

    DB Alloy micro adjust


    DB Race M-series


    DB4L alloy platform


    FSA No.8B, orbit sealed


    KMC X9 EPT


    37 lbs. 15 oz.

    Bike Weight

    Bike weight is based on median size, as sold, or the average of two median sizes.



  • Size Chart

    S M L
    Height Range 5'4" -5'7" 5' 7" - 5' 10" 5' 10" - 6'1"
    Reach 409 435 456
    Stack 596 606 605
    Effective Top Tube 580 609 630
    Seat Tube Center-Top 400 457 500
    Standover Height 787 804 820
    Head Tube Length 110 120 120
    Head Tube Angle (degrees) 68.5 68.5 68.5
    Seat Tube Angle (degrees) 74 74 74
    Bottom Bracket Height 319 319 319
    Wheelbase 1130 1160 1181
    Chainstay 460 460 460
    Fork Offset 50 50 50

    Sizing Notes

    Measurements are stated in millimeters unless otherwise indicated.

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