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.
*Using a 26 x 5.25” tire will cause some drivetrain limitations. For all the nuts and bolts of compatibility read Andy’s blog on the subject.
Select a few bike sizes to compare.
|Reach||16.1 408||17.0 432||17.6 448|
|Stack||22.8 578||23.5 597||24.6 625|
|Head Tube Angle||69.0°||69.0°||69.0°|
|Head Tube Length||3.9 100||4.7 120||5.9 150|
|Seat Tube Length||14.0 356||17.0 432||20.0 508|
|BB Drop||2.2 55||2.2 55||2.2 55|
|Wheelbase||60.3 1532||61.5 1563||62.6 1590|
|Chainstay Length||34.4 875||34.4 875||34.4 875|
|Top Tube Length, Actual||23 584||23.5 598||24.3 617.3|
|Top Tube Length, Effective||23.2 590||24.4 620||25.4 645|
|Seat Tube Angle||72.5°||72.5°||72.5°|
|Standover Height||29.4 746||31.2 792||33.1 841|
|Stem Length||2.4 60||2.8 70||3.1 80|
|Handlebar Width||29.5 750||31.5 800||31.5 800|
|Crank Length||6.7 170||6.9 175||6.9 175|
|Fork Length||18.4 468||18.4 468||18.4 468|
|Fork Rake||1.9 47||1.9 47||1.9 47|
Surly 4130 CroMoly steel. Main triangle double-butted. TIG-welded cargo specific engineered for stiffness and durability.
- Rear Dropouts
Vertical, 197 x 12mm spaced
Vertical, 197 x 12mm spaced, Surly thru axle included
- Brake Compatibility
51mm disc mounts
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
- Seatpost Clamp Diameter
33.1mm (Surly stainless included)
- Headset/Steerer Tube
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
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
HU0139 Surly 15x150 Front Thru Axle
HU0136 Surly 12x197 Rear Thru Axle
Bliolet and Cromwell Green
- Rack Fit Guide
[pdf] - 716KB
- Bike Sizing Chart
[pdf] - 308KB
- Big Fat Dummy Framesheet
[pdf] - 863KB
- Big Fat Dummy Fork Instructions (Wednesday Fork)
[pdf] - 164KB
- Dummy Rail Collar Instructions
[pdf] - 555KB
- Dummy Deck Instructions
[pdf] - 695KB
- Dummy Rail Instructions
[pdf] - 672KB
- Big Dummy/Big Fat Dummy Frame Insert Instructions
[pdf] - 122KB
- Dummy Bag Instructions
[pdf] - 2.4MB
This Surly product is warranted against defects in materials and workmanship for three years from the date of retail purchase of the product, subject to the limitations detailed below. Save your dated receipt for proof of purchase.
This warranty does NOT cover the following:
- Damage due to improper assembly or follow-up maintenance or lack of skill, competence or experience of the user or assembler
- Products that have been modified, neglected, used in competition or for commercial purposes, misused or abused, involved in accidents or anything other than normal use
- Installation of components, parts or accessories not originally intended for or compatible with bicycle as sold
- Damage or deterioration to the paint, surface finish, aesthetics or appearance of the product
- Normal wear and tear
- Labor required to remove and/or refit and re-adjust the product within the bicycle assembly
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