Otso Fenrir Ti Flat Bar


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The Otso Fenrir Ti is ideal for adventurers and bikepackers who prefer an upright riding position, superior braking performance, and plenty of space for accessories on their gravel bike.


Designed with 3Al-2.5V titanium, this frameset is lightweight, strong, and corrosion-resistant with adjustable geometry, large tires up to 29” x 2.6” or 27.5” x 2.8”, and multiple mounts for gear. The flat bar configuration offers an upright riding position, superior braking performance, and plenty of space for accessories.

Recommended rider height 4’10”-5’4″ 5’3″-5’7″ 5’7″-5’11” 5’11”-6’3″ 6’3″-6’6″
Effective top tube 547mm 565mm 583mm 600mm 618mm
Nominal head tube angle 68° 68° 68° 68° 68°
Tuning Chip induced head/seat tube angle change ±0.2° ±0.2° ±0.2° ±0.2° ±0.2°
Head tube length 90mm 100mm 120mm 140mm 160mm
Nominal seat tube angle 75° 75° 75° 75° 75°
Seat tube length 360mm 400mm 450mm 490mm 530mm
Bottom bracket drop 68-72mm 68-72mm 68-72mm 68-72mm 68-72mm
Chainstay length 430-450mm 430-450mm 430-450mm 430-450mm 430-450mm
Wheelbase 1090-1110mm 1110-1120mm 1130-1150mm 1150-1170mm 1170-1190mm
Trail 88mm 88mm 88mm 88mm 88mm
Fork offset 51mm 51mm 51mm 51mm 51mm
Rigid fork axle to crown length 495mm 495mm 495mm 495mm 495mm
Stack 595mm 605mm 623mm 642mm 660mm
Reach 387mm 403mm 416mm 428mm 441mm
Standover 754mm 777mm 810mm 838mm 866mm


Titanium Frame: Constructed from 3Al-2.5V titanium, offering exceptional strength, lightweight performance, and excellent corrosion resistance.

Adjustable Geometry: Features the Tuning Chip™ dropout system, allowing for customization of the wheelbase and bottom bracket height for optimized handling across various terrains.

Generous Tire Clearance: Supports tires up to 29” x 2.6” or 27.5” x 2.8”, providing versatility for different riding surfaces and enhancing off-road capabilities.

Mounting Options: Equipped with multiple mounts for racks, fenders, and gear, making it ideal for bikepacking, long-distance touring, and carrying all necessary equipment for extended adventures.

Flat Bar Configuration: Provides superior control and comfort, especially on technical terrains and long rides, making it a capable and confident gravel bike setup.


Most components can be customized at time of order, contact us!

Frame 3Al/2.5V B338 grade 9 titanium 3Al/2.5V B338 grade 9 titanium
Fork Carbon Lithic Mountain Fork, 15mm thru axle Carbon Lithic Mountain Fork, 15mm thru axle
Headset Wolf Tooth Performance Headset Wolf Tooth Performance Headset
Rear derailleur Shimano GRX 822 1x, 12-speed Shimano SLX M7100, 12-speed
Front derailleur N/A N/A
Shifters Shimano GRX 600 mechanical, 12-speed Shimano SLX M7100, 12-speed
Cassette Shimano SLX M7100, 11-51T, 12-speed Shimano SLX M7100, 10-51T, 12-speed
Brakes Shimano RX400 Hydraulic Shimano Deore BR-6100
Cranks Race Face Aeffect, 34T Chainring Race Face Aeffect, 34T Chainring
Handle-bar Lithic Corundum aluminum compact drop with 16° flare Aluminum, 31.8mm x 780mm, 20mm rise
Tape / Grips Anti-Slip Gel Bar Tape Wolf Tooth Grips
Wheels DT Swiss M1900 29″ DT Swiss M1900 29″
Tires Maxxis Aspen 29 x 2.4 WT Tubeless Ready, Dual Compound, EXO protection Maxxis Aspen 29 x 2.4 WT Tubeless Ready, Dual Compound, EXO protection
Frame Sizes XS, S, M, L, XL XS, S, M, L, XL
Bottom bracket standard Shimano english thread BSA, Ø73mm
Maximum chainring size 1x: 40T round or 38T oval
Front derailleur type N/A
Headset ZS44/28.6 upper, EC44/40.0 lower
Seatpost diameter Ø31.6mm
Internal dropper post routing Yes. Exit port on bottom of seat tube
Seatpost clamp Ø34.9mm
Front/rear hub standard 110x15mm thru axle / 148x12mm thru axle
Front/rear axle Ø15x110mm front, TP=1.5, TL=15mm / Ø12x187mm rear, TP=1.5, TL=12mm
Derailleur hanger Wolf Tooth Tuning Chip Right Dropout
Rear brake (rotor) Flat mount, 74mm post mount available(160mm)
Front brake (rotor) Post mount native, (160mm post mount or 180mm flat mount)
Fork axle-to-crown 490mm (suspension corrected for 100mm suspension fork)
Fork offset 44mm or 52mm
Bare frame weight (L) 3.9lbs (1814g)
Fork weight (Enve rigid fork) 676g
Tire clearance (frame) 2.3″ at 420mm chainstay position, 2.8″ (for 27.5″ wheels) or 2.6″ (for 29″ wheels) at 430/440mm chainstay positions
Tire clearance (fork) Max clearance 29″ x 3.0″
Braze-ons Three bottle frame mounts, fender, rack, cable clamps, two three-pack mounts on fork
Frame Bag Dimensions X-Small Small Medium Large X-Large
Seatpost Insertion Depth X-Small 180mm; Small 200mm; Medium 250mm; Large 280mm; X-Large 320mm
Max weight (rider + gear) 275 lbs
Max spacer stack under stem 40mm
Max spacer stack above stem 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.