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Mongoose

Mongoose Flatrock 21-Speed Hardtail Mountain Bike, 24 to 29-Inch Wheels, for Men Women Boys and Girls, Front Suspension, 14.5 to 18-Inch Aluminum Frame Options

  • Based on 383 reviews
Condition: New
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Availability: In Stock.
Fulfilled by Amazon
Arrives Friday, Aug 1
Order within 4 hours and 44 minutes
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Color: Red


Size: 18-Inch Frame/29-Inch Wheels


Features

  • ADULT MOUNTAIN BIKE: Get ready to explore new trails on the Flatrock by Mongoose. Featuring 29-inch wheels, this bike is perfect for riders from 5'4" - 6'2" tall. Roll over difficult terrain with ease.
  • BORN IN DIRT: Lightweight yet durable with a 6061 aluminum hardtail frame, this womens and mens mountain bike is ready to explore off the bike path and keep up with adventurous riders.
  • BUILT FOR ADVENTURE: This Mongoose mountain bike is ready to roll with knobby mountain tires and double wall alloy rims for durable traction. The suspension fork absorbs bumps and uneven terrain, ensuring a smooth, controlled ride.
  • SHIFT INTO GEAR: This 21-speed bike boasts twist shifters and a rear derailleur for smooth shifting and the right gear for your ride. Mechanical disc brakes provide reliable stopping power in varied conditions, giving riders control on rough terrain.
  • KNOW YOUR ROOTS: As one of the OGs in BMX and action sports, Mongoose has helped bring this movement to the world. For over 50 years, we've been all about epic rides and pushing limits and we're just getting started.

Description

Explore rad new trails with the Flatrock mountain bike by Mongoose. The Flatrock comes equipped with a lightweight aluminum hardtail frame and Element suspension fork that are ready to tear down the trail. 21-speed twist shifters and rear derailleur provide effortless gear changes, while alloy v-brakes deliver reliable stopping power. Plus, double wall alloy rims offer lightweight durability. Get out there and explore with the Mongoose Flatrock.

Bike Type: Mountain Bike


Age Range (Description): Adult


Brand: Mongoose


Number of Speeds: 21


Color: Red


Wheel Size: 29 Inches


Frame Material: Aluminum


Suspension Type: Front


Special Feature: Lightweight


Included Components: Flatrock Bike


Bike Type: ‎Mountain Bike


Age Range (Description): ‎Adult


Brand: ‎Mongoose


Number of Speeds: ‎21


Color: ‎Red


Wheel Size: ‎29 Inches


Frame Material: ‎Aluminum


Suspension Type: ‎Front


Special Feature: ‎Lightweight


Included Components: ‎Flatrock Bike


Size: ‎18-Inch Frame/29-Inch Wheels


Brake Style: ‎Linear Pull


Item Weight: ‎16.8 Kilograms


Style: ‎Bike


Model Name: ‎Flatrock


Wheel Material: ‎Aluminum


Year: ‎2021


Seat Material Type: ‎Plastic or synthetic material


Assembly Required: ‎Yes


Is Autographed: ‎No


Number of Handles: ‎21


UPC: ‎038675236325


Manufacturer: ‎Pacific Cycle, Inc


Item Package Dimensions L x W x H: ‎58 x 29 x 8 inches


Package Weight: ‎19.5 Kilograms


Brand Name: ‎Mongoose


Warranty Description: ‎Limited Lifetime


Material: ‎Aluminum


Suggested Users: ‎unisex-adult


Part Number: ‎R5864


Date First Available: December 10, 2020


Frequently asked questions

If you place your order now, the estimated arrival date for this product is: Friday, Aug 1

Yes, absolutely! You may return this product for a full refund within 30 days of receiving it.

To initiate a return, please visit our Returns Center.

View our full returns policy here.

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Leasing options through Acima may also be available during checkout.

Learn more about financing & leasing here.

Similar Products

Top Amazon Reviews

    • My Go-To for Fun and Adventure!
Color: Silver Size: 17-Inch Frame/26-Inch Wheels
If you're looking for a bike that's ready for anything, whether it's cruising around the neighborhood or hitting some easy trails, the Mongoose Flatrock is an awesome choice. I've been riding mine, and it's just a fantastic, reliable bike that makes getting out and about a joy. First off, it's really comfortable to ride. The front suspension (that's the "hardtail" part, meaning suspension in the front fork) does a great job soaking up bumps and uneven paths, so your arms and body don't take a beating. This makes longer rides or slightly rougher terrain much more enjoyable. Changing gears is super easy with the 21-speed twist shifters. Whether you're going uphill and need a lower gear, or flying downhill and want to pick up speed, a simple twist of the wrist gets you where you need to be. It shifts smoothly, so you're never struggling to find the right gear. I also really appreciate how lightweight yet sturdy it feels. It's easy to maneuver, which is great for weaving through paths or even just getting it on and off a bike rack. And when you need to stop, the brakes are reliable and give you plenty of stopping power. Overall, the Mongoose Flatrock is a fantastic bike for anyone who wants to enjoy the outdoors. It's built tough, rides smoothly, and is just a lot of fun. Whether you're a casual rider or looking to explore a bit more, this bike is a great companion! ... show more
Reviewed in the United States on May 22, 2025 by Burning Man
    • Doesn’t come with tools
Color: Grey Size: 17-Inch Frame/26-Inch Wheels
Hard to assemble really good quality delayed 2 times size is good good for its money does not come with tools to assemble the bike.
Reviewed in the United States on June 11, 2025 by Syed Abbas
    • Easy to Assemble and Meets My Needs
Color: Purple Size: 16-Inch Frame/26-Inch Wheels
I live in a medium-sized neighborhood; I bought this bike to more easily travel within my neighborhood without having to use my car for very short trips. I have never assembled a bike before, but I was able to assemble this one quite easily. The instructions were a bit confusing, because instructions are included for several different versions of the bike, but once I acclimated to which instructions were applicable to me, it wasn't very hard. I did have to purchase a few items for assembly, but they were not very costly, and they will be useful additions to my toolbox. Assembly really only entailed attaching the handlebars, seat and pedals. All of the gear mechanism was already assembled. The bike is easy to ride and operate. So far, I'm completely satisfied with this purchase! ... show more
Reviewed in the United States on October 20, 2022 by Wendi McDaniel
    • Mongoose bike
My grandson was delighted !!
Reviewed in the United States on December 14, 2024 by Kindle Customer
    • Not well made, parts already braking, no customer support
Color: Red Size: 18-Inch Frame/29-Inch Wheels
My husband and I recently bought the above bike on Amazon for our son for his birthday. We studied reviews and felt good about this being a good bike for a big kid--he's almost 6' and a stout guy. He loved the look of the bike; however, after a couple weeks of use, we've been very disappointed in the quality and functions of the bike. Here are several items of note: 1) The handle bar--this bar, although sleek looking, does not offer much room for adjustment and it is very uncomfortable, even painful, to ride for our son, me (5'8") and my husband (6'1"). We all experienced pinched shoulders and neck even after riding it just around the block. A neighbor helped us put a different handlebar in to raise the grip a bit, and although it helps, it's not quite the right size for the bike, the overall grip is still pretty narrow. Which means we will have to keep shopping around to make adjustments. 2) The handle grips and gear shift--these are entirely too small and spaced too close together! My son's hand, if he grips with a standard 4 finger grip, overlaps with the gear shift, so gears are shifting when he's just holding on to the handlebars and not meaning to shift gears. 3) The pedal/crank set--there is a decent amount of wiggle room in this. As I understand, this should be a pretty sturdy feel, but it jiggles. It doesn't appear that this is anything we can adjust, it is as it came. We had the bike professionally put together, and the mechanic noted this right away. 4) The kickstand--it has already bent and bends forward with the weight of the bike and no longer works. Overall, we are extremely disappointed in this bike. We feel that for the money, we shouldn't be having all these issues right away with it. We reached out to the manufacturer, and have not heard any response back. I'd shop for a different bike! ... show more
Reviewed in the United States on August 2, 2023 by Joe Wilkins
    • Puede mejorar la calidad
Color: Red Size: 18-Inch Frame/29-Inch Wheels
Par de rasguños y las gráficas como mal pegadas con bolsitas en algunas partes . 👍🏼
Reviewed in the United States on May 20, 2025 by Edgar Ortiz
    • Mongoose Bikes At Their Best!!
Color: Red Size: 18-Inch Frame/29-Inch Wheels
Legendary reliability and development on full display with this large, capable, and comfortable Mongoose mountain bike!
Reviewed in the United States on September 5, 2024 by Carlos Ubirlea
    • Beautiful bike.
Color: Silver Size: 17-Inch Frame/26-Inch Wheels
Beautiful bike. Had to get the tool separate to set it up. The set up was a bit more difficult than I anticipated, but defiantly worth it for the finished product. It had a quality frame and beautiful tires, as well as the beautiful blue color through out. Would recommend for an overall quality bike for anyone looking to purchase. Thanks to the seller. ... show more
Reviewed in the United States on January 17, 2025 by Amazon Customer

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