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Otso Arctodus

Otso Arctodus
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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. 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 frame can be attached via mounts on the seat stays and Tuning Chip hardware. Even the geometry is catered for exploration, with extra trail for optimal flotation and bottom bracket height that will ride above deeper 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. Even the BB height was selected for clearance in deep snow.

Snowy trails are good with dropper posts, too. A port near the bottom bracket fits a cable and housing for a cable-actuated dropper post.

Geo Chart

Geometry Chart:
Recommended Rider Height 4' 9" - 5' 5" 5' 5" - 5' 9" 5' 9" - 6' 1" 6' 1" - 6' 7"
Effective top tube (mm) 589 610 632 657
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 (mm) 90 90 100 120
Nominal seat tube angle 74 ° 74 ° 74 ° 74 °
Seat tube length (mm) 380 420 465 510
BB drop (mm) 78 - 82 78 - 82 78 - 82 78 - 82
Chainstay length (mm) 440 - 460 440 - 460 440 - 460 440 - 460
Wheelbase (mm) 1119 - 1139 1140 - 1160 1162 - 1182 1189 - 1209
Trail (mm) 94 94 94 94
Fork offset (mm) 51 51 51 51
Rigid fork axle - crown length (mm) 485 485 485 485
Stack (mm) 607 607 617 635
Reach (mm) 415 435 455 475
Standover (mm) 707 736 773 810


Frame Chromoly with Tuning Chip® dropout system
Fork Lithic Carbon Fat Fork, suspension corrected, tapered steerer tube, 485mm axle-to-crown, 51mm offset, with bottle mounts
Wheels Lithic Rhyolite 90 26" 84mm with Lithic Hubs
Axles Wolf Tooth
Tires Terrene Johnny 5 Light 26x4.8
Bottom Bracket Race Face BSA 100mm
Crankset Race Face Aeffect 100mm spindle and custom offset Wolf Tooth CAMO system
Chainrings Wolf Tooth 30T
Shifters Shimano SLX M7100 Trigger, 12-speed
Rear Derailleur Shimano SLX M7100, 12-speed
Cassette/Freewheel Shimano SLX M7100, 10-51t, 12-speed
Chain Shimano SLX 12-speed
Brakes Magura MT4
Handlebars Race Face Ride, 740mm riser
Tape/Grips Wolf Tooth grips
Stem Aluminum
Headset Wolf Tooth Performance Headset, ZS44/EC44
Seatpost Aluminum, 31.6mm
Saddle WTB Volt Medium, 142mm width
Pedals Sold Separately

* Subject to change without notice.