Gravity

Gravity Bullseye Monster Fat Bike Frame Kit

5.0 (3 reviews)

Fat bike frame kit with aluminum frame, steel fork, and pre-installed headset ready for your custom 26-inch build.

$199.00*
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*Price sourced from Amazon.com. Last updated:Jul 14, 2026.Price and availability are subject to change.

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Overview

The Gravity Bullseye Monster is a fat bike frame kit that gives builders the structural foundation they need to assemble a custom 26-inch fat bike. The frame is constructed from 6061 aluminum alloy, a material widely used in cycling for its favorable strength-to-weight ratio and corrosion resistance. Paired with a rigid CrMo steel fork, the combination delivers a sturdy front end that absorbs some road vibration naturally, even without a suspension system. The frame's 170mm rear dropout spacing and the fork's 135mm front spacing are standard fat bike measurements, ensuring compatibility with a broad selection of fat bike hubs and wheelsets available on the market.

What sets this kit apart from a bare frame purchase is the inclusion of several pre-installed and ready-to-use components. The headset and stem come already pressed in and mounted, eliminating the need for a headset press tool and the alignment work that comes with it. A seatpost and seatpost clamp are also included, so once you add your own wheelset with up to 26 x 4.0-inch tires, a crankset, bottom bracket, brakes, handlebars, and a drivetrain, you have a complete fat bike. The Matt Nautical Blue finish gives the frame a clean, understated look. This kit is best suited for builders who enjoy the process of selecting and assembling individual components and who want an affordable aluminum platform to start from.

Key Features

Aluminum Frame with Steel Rigid Fork

170mm rear spacing 135mm front spacing

Will Accept 26 x4.0 Tires

Seatpost and Seatpost Clamp Are Included

Headset and Stem are Included and Installed!

Specifications

Brand
Gravity
Model
Bullseye Monster
Frame Material
6061 Aluminum Alloy
Fork Material
CrMo Steel (Rigid)
Wheel Size
26 inch
Max Tire Size
26 x 4.0
Rear Spacing
170mm
Front Spacing
135mm
Included
Frame, Fork, Headset (installed), Stem (installed), Seatpost, Seatpost Clamp
Color
Matt Nautical Blue

Pros & Cons

👍 Pros

  • Headset and stem come pre-installed, saving time and the need for specialized press tools
  • 6061 aluminum frame offers a lightweight yet strong foundation for a fat bike build
  • 170mm rear and 135mm front spacing are standard fat bike dimensions compatible with widely available wheelsets
  • CrMo steel fork provides durability and natural vibration absorption on rough terrain
  • Includes seatpost and clamp so you can focus your remaining budget on wheels and drivetrain

👎 Cons

  • Rigid steel fork offers no suspension travel, which limits comfort on very rough or rocky trails
  • Does not include wheels, tires, drivetrain, brakes, or handlebars — significant additional investment required to complete the bike
  • Limited publicly available geometry data makes it difficult to assess fit before purchasing
  • Only available in one color option (Matt Nautical Blue)
  • Frame-only kits appeal mainly to experienced builders who already own or can source compatible parts

Frequently Asked Questions

The kit includes the aluminum frame, CrMo steel rigid fork, headset (installed), stem (installed), seatpost, and seatpost clamp. Wheels, tires, drivetrain, brakes, handlebars, and pedals are not included.
The Gravity Bullseye Monster frame accommodates up to 26 x 4.0-inch fat bike tires, which is standard for most fat bike builds.
The rear dropout spacing is 170mm and the front fork spacing is 135mm. Make sure your wheelset hubs match these dimensions before purchasing.
The included fork is a rigid CrMo steel fork. There is no suspension. If you want front suspension, you would need to source a compatible suspension fork separately with 135mm spacing.
The frame is made from 6061 aluminum alloy, which provides a good balance of light weight and durability. The fork is CrMo steel for added strength and vibration dampening.