Overview
The Otso Fenrir Stainless Frameset is designed for ultimate versatility and adventure. Built from custom-butted austenitic stainless steel, it offers a smooth ride and excellent corrosion resistance. The frame supports both drop bars and MTB flat bars, allowing customization based on your riding style.
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Every last feature of Fenrir is optimized for bikepacking. The stainless steel frame is strong, comfortable, and surprisingly light weight. It can be built with flat bars or drop bars depending on your affinity for large handlebar rolls. Single speed is an option for folks who like simplicity while touring. It has extra mounts on the frame and fork for hauling all the gear you‘ll need for days (or weeks) on the trail. No matter your destination and how long it takes to get there, Fenrir is ready.
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Features
Versatile Frame Material: Custom-butted austenitic stainless steel offers a smooth ride and excellent corrosion resistance.
Adjustable Geometry: Tuning Chip™ dropout system allows you to adjust the wheelbase (up to 20mm), bottom bracket height (4mm), and head tube angle (0.2°) for optimal handling.
Multiple Configurations: Compatible with drop bars or MTB flat bars, accommodating different riding styles for gravel or mountain biking.
Generous Tire Clearance: Fits up to 29” x 2.6” or 27.5” x 2.8” tires, making it suitable for various terrains.
Comprehensive Mounting Options: Equipped with multiple mounts on the frame and fork for racks, fenders, and gear, ideal for bikepacking and long-distance touring.
Customization: Available in five sizes (XS to XL) and supports mechanical/electronic drivetrains, single speed setups, and suspension forks up to 100mm of travel.
Specs
Frame Specs
| 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 120mm 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 |
| 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 |
Geometry
| 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 from middle position | ±0.25° | ±0.25° | ±0.25° | ±0.25° | ±0.25° |
| 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 |
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.