Surly Big Dummy Cargo Frame Set

The Surly Big Dummy frameset is the perfect foundation for an extremely robust, versatile and durable longtail cargo bike. Since 2008, the Big Dummy has been helping families, commuters and business owners to reduce their car use, transport loads efficiently and make their everyday lives more sustainable. The robust 4130 chromoly frame with Surly Natch Tubing offers maximum stability, minimises torsional flex and stays perfectly on track even when fully loaded.

Sizes: S, M, L

Colour: Twilight Zone

Current delivery dates: September 2026 – Pre-order

Please enquire for the latest status

Specifications:

Frame & Fork

• Frame: 4130 chromoly, Surly Natch Tubing, double-butted, TIG-welded
• Fork: 4130 chromoly, Natch Tubing, double-butted, tapered fork legs, TIG-welded, E.D. coated
• One-piece frame design for maximum stiffness
• Colour: depends on model year
• Rigid fork length: 420 mm
• Offset: 45 mm

Cargo features

• Includes Dummy Deck, Dummy Rails, Dummy Rail Collars & Big Dummy Bags (Version 2.0)
• Compatible with child transport (Dummy Rail Collars)
• Centre-mount kickstand made from high-strength alloy
• 400 lb total load capacity (rider + luggage)

Tyre & wheel specifications

Frame:

• 26 x 2.0–2.5" with mudguard
• 27.5 x 1.5–2.0" with mudguard
• 700c x 28–32 mm with mudguard

Fork:

• 26 x 3.0" without mudguard
• 26 x 2.75" with mudguard
• 27.5 x 2.8" without mudguard
• 27.5 x 2.5" with mudguard
• 29 x 2.1" without mudguard
• 29 x 1.9" with mudguard

Brakes & Standards

• Brake mount: 51 mm I.S. disc
• Max. rotor size: 203 mm front & rear
• Headset: EC34/28.6 top, EC34/30 bottom
• Steerer: 1 1/8" (Ø28.6 mm)
• Crown race: Ø30 mm

Drivetrain & compatibility

• Rohloff compatible
• Bottom bracket: 73 mm BSA (1.37" x 24 TPI)
• Front derailleur: High Direct Mount, top-pull (Ø34.9 mm), 26 mm offset adapter
• Max. chainring size: no frame restriction

Mounting points

• Bottle cage mounts:
  • SM: 2 standard + 1 three-pack
  • MD/LG: 3 standard + 1 Three-Pack
• Fork: 2 Four-Pack mounts
• Front & rear mudguard mounts

Geometry & dimensions

• Seat tube: Ø30.9 mm (dropper seatpost compatible)
• Seat clamp: Ø33.1 mm
• Max. seatpost insertion depth:
  • SM: 375 mm
  • MD: 255 mm
  • LG: 331 mm
• Rear dropouts: 10 x 135 mm
• Front dropout: 10 x 100 mm

Big Dummy frame set – Custom build in our workshop

The Surly Big Dummy frame set is the ideal basis for a durable, highly stable longtail cargo bike. Made from 4130 chromoly Natch tubing and designed as a one-piece frame for maximum stiffness, it offers the perfect conditions for heavy loads, everyday transport and adventure. With a payload of up to 400 lb and clearance for wide tyres, the Big Dummy is a robust platform for families, commuters and commercial use.

At our a-bikeshop workshop , we build your Big Dummy entirely to your specifications – exactly to your requirements. Whether it’s a Rohloff hub, CUES setup, cargo configuration, child transport or touring kit: we plan, assemble and optimise every detail for maximum everyday practicality and reliability.

The benefit for you: you won’t get a standard bike, but a bespoke cargo bike, built by specialists who have known Surly inside out for years.