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    Big adventures require a bike that can rise to the occasion. Arctodus is named after Arctodus simus, an Ice Age behemoth that was the largest bear to ever walk the Earth. Like its namesake, Arctodus the bike is versatile, strong, and ready to explore. It has adjustable geometry, a durable steel frame, a massive front triangle for a frame bag, lots of cargo mounts, and can clear the biggest fat bike tires on the market. Arctodus is ready for afternoon exploration, polar expeditions, and everything in between.


    Arctodus was built around a 26" x 4.8" tire for optimal handling and control on loose trails. It can fit the biggest fat bike tires in the world. The biggest fat tire on the market is 26" x 5.05" and Arctodus eats them like a snack with room to spare. Same as 27.5" x 4.5", which is the biggest 27.5" tire available. Arctodus is the only bike to clear tires this big with a 12-speed drivetrain without chain interference. When a bike is created for big rides with fresh snow, it needs to fit tires that were designed for the same reason. This is a bike that prays for snow and cuts its own trail.


    A key feature in all Otso bikes is adjustable geometry and the ability to adapt the bike for the ride ahead. The patented Tuning Chip rear dropout system can change wheelbase length by up to 20mm, raise or lower the bottom bracket height by up to 4mm, and change the head tube angle by +/- 0.5º. Use the rear position when the trails are loose and you need as much control as you can get. Use the front position when the snow is firm and the trails let you take turns with a little speed. This frame is also compatible with Wolf Tooth GeoShift 1º and 2º Angle Headsets, effectively unlocking five head tube angles from 66.5º to 70.5º. No matter the conditions, Arctodus has an answer.


    There's no need to wait for the trail groomer. Arctodus was made for foot trails, forest paths, and snow-covered frozen lakes. The bombproof steel frame can withstand the demands of an expedition. A large front triangle can fit a healthy full frame bag. The carbon fork has mounts on either side for cargo. A rear rack can be attached via mounts on the seat stays. Even the geometry is catered for exploration, with extra trail for optimal flotation and bottom bracket height that's friendly with deep snow. Whether you're exploring local trails or a national forest, you can trust Arctodus to keep you riding.



    Arctodus has a 100mm bottom bracket. This is 30-40mm narrower than other fat bikes that have the same tire clearance. Ride with massive tires without compromising handling.


    All Otso frames feature suspension-corrected geometry. Arctodus is compatible with suspension forks that have up to 120mm of travel. A few options are available on the Custom Bike Builder.


    Arctodus geometry was designed for optimal riding on fresh trails. The 68º head tube angle paired with massive tires gives Arctodus more trail than other fat bikes.


    Snowy trails are good with dropper posts, too. A port near the bottom bracket fits a cable and housing or hydraulic hose for dropper posts that require internal frame routing.


    Frame Chromoly with Tuning Chip™ dropout system
    Fork Lithic carbon fat fork, suspension corrected, tapered steerer tube, 485mm axle-to-crown, 51mm offset
    Headset Wolf Tooth Performance Headset, ZS44/EC44
    Rear derailleur Shimano SLX M7100, 12-speed
    Front derailleur None, 1x only bike
    Shifters Shimano SLX M7100 Trigger, 12-speed
    Cassette Shimano SLX M7100, 10-51t, 12-speed
    Brakes Magura MT4
    Cranks Race Face Aeffect with Wolf Tooth CAMO System P2 (+4mm offset) spider, 30T chainring
    Bottom bracket Race Face, BSA 100mm
    Handlebar Race Face Ride, 740mm riser
    Grips Wolf Tooth grips
    Stem Aluminum
    Seatpost Aluminum, 31.6mm
    Seat WTB Volt Medium, 142mm width
    Wheels Lithic Rhyolite 90 26" 84mm with Lithic Hubs (rear hub offset 5mm)
    Tires Terrene Johnny 5 Light 26"x4.8"
    Chain Shimano SLX 12-speed
    Frame Sizes S, M, L, XL
    Bottom bracket standard 100mm BSA threaded
    Q-factor 205mm with Race Face Aeffect crankset
    Maximum chainring size 36T round or 34T oval
    Front derailleur type None. 1x only bike.
    Headset ZS44 upper, EC44 lower
    Seatpost diameter Ø31.6mm, accommodates internally routed dropper post
    Seatpost clamp Ø34.9mm
    Front/rear hub standard 150x15mm thru axle / 197x12mm thru axle offset 5mm to drive side (rear wheel must be dished 5mm)
    Front/rear axle Ø15x150mm, TP=1.5, TL=12mm / Ø12x235mm, TP=1.5, TL=14mm
    Rear Dropouts Tuning Chip Dropout with adjustable chainstay length, offset 5mm
    Derailleur hanger Tuning Chip Right Dropout
    Rear brake (rotor) 74mm post (160mm native, 180mm max)
    Front brake (rotor) 74mm post (160mm native, 180mm max)
    Fork axle-to-crown 485mm, suspension corrected for 100-120mm travel forks
    Fork offset 51mm
    Bare frame weight (size M) 3410g
    Fork weight (Otso rigid fork) 650g
    Tire clearance (frame) Up to 26"x5.25" or 27.5"x4.5" or 29"x3" in all Tuning Chip positions
    Tire clearance (fork) Up to 26"x5.4" on 100mm rim
    120mm fork note Using a 120mm suspension fork with slacken the head tube angle by 0.5˚
    Frame Bag Dimensions Small Medium Large X-Large
    Frame Size Small Medium Large X-Large
    Recommended rider height 4'9"-5'5" 5'5"-5'9" 5'9"-6'1" 6'1"-6'7"
    Recommended rider inseam 29"-32" 31"-33" 32"-35" 34"-37"
    Effective top tube 589mm 610mm 632mm 657mm
    Nominal head tube angle 68.5° 68.5° 68.5° 68.5°
    Tuning Chip induced head/seat tube angle change ±0.2° ±0.2° ±0.2° ±0.2°
    Head tube length 90mm 90mm 100mm 120mm
    Nominal seat tube angle 74° 74° 74° 74°
    Seat tube length 380mm 420mm 465mm 510mm
    Bottom bracket drop 80mm 80mm 80mm 80mm
    Chainstay length 440-460mm 440-460mm 440-460mm 440-460mm
    Wheelbase 1119-1139mm 1140-1160mm 1162-1182mm 1189-1209mm
    Trail 94mm 94mm 94mm 94mm
    Fork offset 51mm 51mm 51mm 51mm
    Rigid fork axle to crown length 485mm 485mm 485mm 485mm
    Stack 607mm 607mm 617mm 635mm
    Reach 415mm 435mm 455mm 475mm
    Standover 707mm 736mm 773mm 810mm

    Compatible fenders

    PDW - Mud Shovel Front and Rear Fenders

    SKS - Fatboard Fender Set


    compatible racks

    Salsa - Alternator Rear Rack 190 / 197

    Topeak - Uni Super Tourist Fat Rear Rack

    Blackburn - Outpost Fat Rear Rack

    Surly - Rear Disc Rack Wide


    Frame Bag Dimensions

    (click on links to view PDF drawings)







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