GT 27.5 Avalanche Sport Bike

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Color: Blue
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Pursue new thrills on dirt trails and gravel paths with the GT 27.5 Avalanche Sport bike. This hardtail is built for the rider that seeks efficiency, versatility and fun off-road.

  • Features

    • Completely redesigned alloy frame is stable and durable; features Boost 141 forged dropouts with disc brake mounts
    • Floating seatstays provide additional compliance and comfort
    • Internal cable routing allows for a clean look; includes dropper post routing (dropper post not included)
    • Locking 100 mm front fork transitions smoothly from dirt trails to gravel paths
    • Tektro hydraulic disc brakes provide controlled stopping power
    • Closeout
    • Specs and images are subject to change


    This bike comes with Coast to Coast Support, which includes:
    • 1 year of free adjustments (see more below)
    • In-store bike assembly
    • Pickup in store or curbside
    • Bike experts available at 170+ bike shops
    REI Co-op Members get more:
    • Free flat tire repairs (labor only; parts not included)
    • 20% off shop services
    More about our free adjustments:
    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 GT Hardtail Mountain Bikes
  • Technical Specs

    Best Use

    Mountain Biking

    Mountain Bike Style



    GT 6061 T6 aluminum Triple Triangle with floating seatstays; zero stack tapered 1-1/8 to 1.5 in. head tube

    Bike Suspension

    Front Suspension


    SR Suntour XCT-DS, 100 mm, hydraulic lockout and preload adjust, coil

    Fork Travel

    100 millimeters


    Prowheel Alloy, 36/22T

    Bottom Bracket

    Cartridge, Square Taper


    39-29T, 9-speed

    Front Derailleur

    Shimano Altus

    Rear Derailleur

    microSHIFT RD-M36L

    Rear Cogs


    Number of Gears

    18 gear(s)

    Brake Type

    Hydraulic Disc Brake


    Tektro M275 Hydro Disc, 160/160 mm Rotors

    Brake Levers

    Tektro M275 Hydro Disc


    WTB SX19, 32 h

    Front Hub

    Alloy disc, 100 mm quick-release

    Rear Hub

    Alloy disc, 141 mm quick-release

    Wheel Size

    27.5 inches


    WTB Ranger Comp, 27.5 x 2.25 in., DNA Compound

    Tire Width

    2.25 inches

    Handlebar Shape

    Riser Bar


    GT All Terra Alloy Riser, 25 mm Rise, 8° Sweep, 6° Rise, 720mm Width


    GT All Terra, 6061 Alloy, 31.8, 8°

    Seat Post

    GT All-Terra Micro Adjust Alloy Seat Post, 30.9mm


    GT MTB


    GT Slim Line Flat Pedal


    Semi-integrated, Sealed Cartridge, Tapered


    KMC Z9, 9-speed





  • Size Chart

    Seat Tube Center-Top35.5384348.5
    Standover Height69.871.775.279.1
    Head Tube Length9101112
    Head Tube Angle (degrees)68.568.568.568.5
    Seat Tube Angle (degrees)73737373
    Bottom Bracket Height30.
    Fork Offset4.

    Sizing Notes

    Measurements are stated in centimeters unless otherwise indicated.

    How we measure bikes

    1. Standover Height Standover Height is a measurement from the ground to the top of the top tube, measured at the midpoint of the top tube.
    2. Reach Reach is the horizontal distance from the center of the cranks to the center of the head tube, measured at head tube level.
    3. Stack Stack is the vertical distance from the center of the cranks to the center of the head tube, measured to the top of the head tube.
    4. Effective Top Tube Effective top tube is the distance from the center of the head tube to the center of the seat tube/seat post, measured parallel to the ground.
    5. Seat Tube Center to Top Seat Tube length is the measurement of the seat tube, from the center of the cranks to the top of the seat tube.
    6. Head Tube Length Head Tube Length is measured from the bottom to the top of the head tube.
    7. Head Tube Angle Head Tube Angle is the acute angle between the head tube and the ground (measured towards the rear of the bike)
    8. Seat Tube Angle Seat Tube Angle is the acute angle between the seat tube and the ground (measured towards the rear of the bike).
    9. Bottom Bracket Height Bottom Bracket Height is a measurement taken vertically from the ground up to the center of the cranks.
    10. Wheelbase Wheelbase is the measurement from the center of the front axle to the center of the rear axle.
    11. Chainstay Length Chainstay Length is the measurement from the center of the cranks to the center of the rear axle.
    12. Fork Offset Fork Offset, or rake, is the distance from the front axle to a line drawn parallel to the center of the head tube or steering axis.
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