Otso Arctodus Frame


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The Otso Arctodus Frameset is your go-to for conquering extreme conditions such as snow, sand, and rugged trails. With tire clearance from 27.5″x3.8″ to 26″x5.05″, it adapts to any terrain. Ready for winter trails or wild adventures, the Arctodus keeps up with your every move.


The Otso Arctodus Frameset is built for the serious fat bike enthusiast who loves tackling extreme conditions. Made from Chromoly with a carbon fork, this frameset is incredibly durable and  strikes a perfect balance between comfort and performance, making it a great choice for snow, sand, and rough trails.

One of the standout features of the Arctodus is its tire clearance. It can fit a wide range of tire sizes, from 27.5″x3.8″ to 26″x5.05″, so you can choose the best option for the terrain you’re riding. Whether you’re navigating winter trails or exploring uncharted paths, the Arctodus Frameset is designed to keep up with your adventures.


Frame and Fork: The Arctodus is built with a Chromoly steel frame for durability and a Lithic carbon fork equipped with Anything Cage mounts, providing ample cargo options.

Tire Clearance: This frameset can accommodate some of the largest tires on the market, fitting up to 26″x5.05″ and 27.5″x4.5″ tires, ensuring maximum traction on any terrain.

Adjustable Geometry: The patented Tuning Chip rear dropout system allows for customizable geometry, letting you adjust the wheelbase by up to 20mm, the bottom bracket height by 4mm, and the head tube angle by +/- 0.5º.

Compatibility: The frame is designed to be compatible with 120mm travel suspension forks, enhancing its versatility and performance on rough trails.

Mounting Options: It features multiple mounting points for racks, fenders, and gear, making it perfect for long expeditions.

Dropper Post Ready: The frameset is dropper post compatible, with internal routing, offering improved handling and control on technical terrain.


Bottom Bracket:

  • 100mm BSA threaded


  • 205mm with Race Face Aeffect crankset

Maximum Chainring Size:

  • 36T round or 34T oval

Front Derailleur:

  • None, 1x only


  • ZS44 upper, EC44 lower

Seatpost Diameter:

  • Ø31.6mm, accommodates internally routed dropper post

Seatpost Clamp:

  • Ø34.9mm

Hub Standards:

  • Front: 150x15mm thru axle
  • Rear: 197x12mm thru axle, offset 5mm to drive side (rear wheel must be dished 5mm)


  • Front: Ø15x150mm, TP=1.5, TL=12mm
  • Rear: Ø12x235mm, TP=1.5, TL=14mm

Rear Dropouts:

  • Tuning Chip Dropout with adjustable chainstay length, offset 5mm

Derailleur Hanger:

  • Tuning Chip Right Dropout

Brake Mounts (Rotors):

  • Rear: 74mm post (160mm native, 180mm max)
  • Front: 74mm post (160mm native, 180mm max)


  • Axle-to-crown: 485mm, suspension corrected for 100-120mm travel forks
  • Offset: 51mm


  • Bare frame (size M): 3410g
  • Fork (Otso rigid fork): 650g

Tire Clearance:

  • Frame: Up to 26″ x 5.25″, 27.5″ x 4.5″, or 29″ x 3″ in all Tuning Chip positions
  • Fork: Up to 26″ x 5.4″ on 100mm rim

120mm Fork Note:

  • Using a 120mm suspension fork will slacken the head tube angle by 0.5°

Frame Bag Dimensions:

  • Small, Medium, Large, X-Large

Seatpost Insertion Depth:

  • Small: 220mm
  • Medium: 270mm
  • Large: 310mm
  • X-Large: 350mm

Max Weight (Rider + Gear):

  • 275 lbs

Spacer Stack:

  • Under stem: Max 40mm
  • Above stem: Max 10mm

Max Stem Bolt Torque:

  • 6 Nm


Warranty Coverage:

  • All Otso frames are warranted against defects in materials and workmanship for 5 years from the date of retail purchase.
  • This warranty applies to the original owner only and is not transferable.
  • Please keep your sales receipt or order number for any warranty claims to ensure a quick resolution.

What’s Not Covered:

  • Damage from improper assembly, maintenance, or user/assembler inexperience.
  • Modifications, neglect, misuse, competition, commercial use, or accidents.
  • Installation of incompatible components, parts, or accessories.
  • Normal wear and tear, or damage to paint, surface finish, or aesthetics.
  • Compatibility of original components with a replacement frame is not guaranteed.
  • Costs for labor, parts removal, refitting, or re-adjustment, including wheel rebuilds.

Claim Process:

  • Warranty claims are limited to the repair or replacement of the defective frame, at Otso’s discretion.
  • This warranty does not cover incidental or consequential damages.

Legal Information:

  • This warranty gives you specific legal rights, which may vary based on location. It does not affect your statutory rights.