Overview
Designed with a custom-butted stainless steel frame, adjustable geometry, large tires up to 29” x 2.6” or 27.5” x 2.8”, and multiple mounts for gear, the Otso Fenrir Stainless Flat Bar is perfect for long-distance touring and bikepacking. The flat bar configuration offers an upright riding position, better braking performance, and ample space for accessories.
| XS | S | M | L | XL | |
| 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 |
Features
Custom-Butted Stainless Steel Frame: Provides a smooth, durable ride with excellent corrosion resistance.
Adjustable Geometry: The Tuning Chip™ system allows customization of the wheelbase, bottom bracket height, and head tube angle for optimized handling on various terrains.
Wide Tire Clearance: Fits tires up to 29” x 2.6” or 27.5” x 2.8”, making it suitable for gravel and rugged trails.
Multiple Mounts for Gear: Equipped with numerous mounts on the frame and fork for carrying racks, fenders, and gear, ideal for long-distance touring and bikepacking.
Flat Bar Configuration: Offers an upright riding position, better braking performance, and ample space for accessories.
Specs
Most components can be customized at time of order, contact us!
| DROP BAR | FLAT BAR | |
| Frame | Custom butted austenitic stainless steel frame | Custom butted austenitic stainless steel frame |
| 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 |
| Handlebar | 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 | Ø15x100mm 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) | 5.7 lbs. (2580g) |
| 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 2.8″ or 27.5″ 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 170mm; Small 210mm; Medium 260mm; Large 290mm; X-Large 330mm |
| 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
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.