M FiftyOne Assassin (GRX/XTR Di2)

Boutique Irish Carbon. Mullet AXS-Killer Speed.

The engineering hallmark of the FiftyOne Assassin is its custom carbon chassis with flip-chip adjustable frame geometry paired with a Shimano XTR/GRX Di2 1x12 drivetrain. Engineered with dual-position flip chips at both the front fork and rear dropouts, the Assassin lets you switch between a snappy, aggressive race handling profile and a long, stable wheelbase setup for rowdy singletrack and chunky gravel. Equipped with a custom 1x12 electronic "Mullet" build featuring an XTR cassette mated to GRX Di2 dual-control levers, it delivers massive climbing range with crisp, wire-free shifting execution.

Why This One Of A Kind Assassin Belongs in Your Garage:

• Tunable Flip-Chip Geometry: Dual front and rear flip-chips adjust trail figure and chainstay length, allowing you to tailor handling for fast road/all-road blasts or high-speed gravel stability.

• Custom Wide-Range Di2 "Mullet" Drivetrain: Combines Shimano GRX RX815 Di2 shifters with an XTR M9250 SGS rear derailleur and 10-51T XTR cassette for massive 510% gear range on steep mountain ascents.

• Shimano RX880 Carbon Gravel Wheelset: Lightweight carbon rims pair with high-volume Continental Terra Speed 45mm tires for explosive acceleration and supple cornering grip.

• Alugear 46T Narrow-Wide Chainring: Precision CNC-machined 1x ring mounted to 165mm Ultegra cranks provides high-torque chain retention and an efficient cadence profile.

• Integrated PRO Carbon Cockpit & Dropper: Features a PRO Discover carbon bar and stem, PRO Stealth saddle, and a dedicated PRO Discover dropper post for steep, technical descents.

Technical Specifications:

• Frame: FiftyOne Assassin Carbon, Flip-Chip Adjustable Geometry, Internal Routing | 12 x 142mm

• Fork: FiftyOne Trident Full Carbon w/ Adjustable Flip-Chip Rake | 12 x 100mm

• Maximum Tire Clearance: 47mm

• Frame Weight: ~1050g

• Mileage: Only 205km (Barely Ridden Shop Demo)

The Build:

1. Frameset & Cockpit

• Frame: FiftyOne Assassin Carbon, Flip-Chip Adjustable Geometry, Internal Routing

• Fork: FiftyOne Full Carbon w/ Adjustable Flip-Chip Rake

• Handlebar: PRO Discover Carbon 40cm

• Stem: PRO Discover 110mm
  
  

• Seatpost: PRO Discover Dropper

• Saddle: Pro Stealth Team

• Bar Tape: PRO Discover

2. Drivetrain (The Groupset)

• Shifters/Brake Levers: Shimano GRX RX815 Di2 Hydraulic

• Rear Derailleur: Shimano XTR M9250 SGS 12Speed Di2

• Crankset: Shimano Ultegra FC-R8100 165mm

• Chainrings: Alugear 1X Aero 46T

• Bottom Bracket: T47 24mm

• Cassette: Shimano XTR CS-M9200 10-51T 12Speed

• Chain: Shimano CN-M6100 (waxed)

3. Braking System

• Calipers: Shimano GRX BR-RX820

• Rotors: Shimano Dura Ace RT-CL900 160/160mm

4. Wheelset & Rubber

• Rims/Wheelset: Shimano GRX WH-RX880 C36

• Tires: Continental Terra Speed 45mm

• Tubeless: w/Silca Sealant

The Alegro Perspective: Finding a boutique Irish-made FiftyOne frame in North America is rare enough. Finding one custom-built with XTR/GRX Di2, RX880 carbon wheels, and a dropper post is completely unheard of. With less than 300km on the clock, this bike isn't even broken in yet. The flip-chip geometry lets you run it tight and aggressive for gravel race days, or stretched out when you want to load up for backcountry singletrack. This is one of the most complete, high-end demo steals to ever hit the shop floor.

Irish Custom Engineering. Ultimate Di2 Mullet Performance. Own a Masterpiece with FiftyOne.