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Big Fat Dummy

Big Fat Dummy

⚠️ WARNING: This product can expose you to chemicals known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.

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The Big Fat Dummy is a long tail cargo bike that took a few too many doses of growth hormones. At first glance, you might say that we just put bigger tires on a Big Dummy. But if you said that, you’d actually be very wrong so just… don’t. Think of Big Fat Dummy as more of a second or third cousin to Big Dummy rather than a brother. They share some of the same DNA and look sort of similar, but they’re two very different bikes and really only interact when they both reach for the potato salad spoon at that family reunion that no one really wants to be at anyway.

Now that that’s out of the way, let’s get down to the nitty gritty of what makes this hulking beast of a bike tick. Our goal with designing a cargo bike around fat tires was to create the most stable, stiff, and traction-laden ride possible while hauling a ton of stuff. Big Fat Dummy has a longer toptube and slacker headtube than its more svelt cousin giving it a nice, predictable, and stable ride. We also used thinner, lighter tubing to construct its cargo area so while it’s an overall burlier bike, there’s not much difference in weight.

Big Fat Dummy accepts either 10mm or 12mm axles in the rear with a spacing of 190/197mm. That big ‘ol spacing equates to one thing: tire clearance for days. Big Fat Dummy maxes out at a massive 26 x 5.25” tire.* While that large of a tire provides the most traction and stability a bike can possibly offer, it’s also a lot of rubber to push and might not be for everybody. Luckily, Big Fat Dummy is also a blast to ride with 3” tires too. It uses the same 100mm suspension-corrected fork as the Wednesday, meaning if you want to add a little squishy squishy to your ride, you can throw a Bluto on and let ‘er rip.

If you intend to carry a passenger on your Big Fat Dummy, Surly requires use of our Dummy Rail Collars. These provide a secondary retention system for the rack, as well as stiffen the rack system. In addition, a stoker handlebar set up, found on tandem bicycles, is recommended as well. Make sure to check with seat post manufacturer for stoker handlebar compatibility. All Big Fat Dummy framesets and bikes ship with a Dummy deck, rails, bags, and the aforementioned Dummy Rail Collars so you can immediately start hauling cargo — human or otherwise.

Big Fat Dummy is ready and willing to carry all sorts of shit — literally. It’s already in use on an organic farm in Ecuador so it’s likely that it’s hauled some form of manure by now.

Specifications

Geometry

Geometry Diagram
SIZE SM MD LG
Reach 408 432 448
Stack 578 597 625
Head Tube Angle 69.0° 69.0° 69.0°
Head Tube Length 100 120 150
Seat Tube Length 356 432 508
BB Drop 55 55 55
Wheelbase 1532 1563 1590
Chainstay Length 875 875 875
Top Tube Length, Actual 584 598 617.3
Top Tube Length, Effective 590 620 645
Seat Tube Angle 72.5° 72.5° 72.5°
Standover Height 746 792 841
Stem Length 60 70 80
Stem Angle
Handlebar Width 750 800 800
Crank Length 170 175 175
Fork Length 468 468 468
Fork Rake 47 47 47

NOTE: The Big Fat Dummy is only available in three sizes, which is a departure from our normal way. Here’s the thing, its sizing and fit is a little different than other bikes. By using shorter seat tubes with a longer seatpost, two people of different heights can ride the same size frame. We found it works pretty well – hell the Large size even fits Sov. And nothing fits Sov.

Frame Specs

  • Tubing: Surly 4130 CroMoly steel. Main triangle double-butted. TIG-welded cargo specific engineered for stiffness and durability.
  • Rear Dropouts - Bliolet: Vertical, 197 x 12mm spaced
  • Rear Dropouts - Cromwell Green: Vertical, 197 x 12mm spaced, Surly thru axle included
  • Brake Compatibility: 51mm disc mounts
  • Braze-ons/extras: Upper and lower tripple bottlecage
    mounts on downtube, Double waterbottle bosses on seatube (not included
    on the small), Surly Trip Guides for continuous brake/shift housing or
    brake hydraulic line (toptube and seatsaty routing), Internal dropper
    post routing
  • Seatpost Diameter: 30.9mm
  • Seatpost Clamp Diameter: 33.1mm (Surly stainless included)
  • Headset/Steerer Tube - Bliolet: 44mm
  • Headset/Steerer Tube - Cromwell Green: ZS44/28.6 upper, EC44/30 lower
  • Front Derailleur Clamp Diameter: 34.9mm, direct mount
  • Bottom Bracket Shell: 100mm wide, threaded English (1.37" x 24t)
  • Chainring Clearance: No frame limitations. Use whatever you want.
  • Tire Clearance: 26 x 5.25", individual tire and rim combos affect tire clearance
  • Fork: Surly Wednesday, Tapered straight blade 4130
    CroMoly. 468mm axle to crown, 47mm offset. 51mm I.S. front standard disc
    mount, 150mm x 15mm thru-axle dropouts (axle included), 100mm
    suspension fork compatible.
  • Thru Axle - Front: HU0139 Surly 15x150
  • Thru Axle - Rear: HU0136 Surly 12x197
  • Colors: Bliolet and Cromwell Green