If you have to ask why, the Surly Big Fat Dummy is probably not for you. But for those looking for a cargo bike that is stiffer, more capable, and will monster over anything in its path, look no further. If you’re not familiar with the original Big Dummy, it’s an extended wheelbase cargo bike that sort of set the scene for two wheeled cargo bikes to come. Long offered in 26″ wheels, the Big Fat Dummy is still 26″, just a whole lot fatter…
Starting with a completely new frame, Surly points out that this is not just a widened Big Dummy. Instead it’s a new bike that drastically increases the tire clearance, but also adds some other benefits at the same time. Just how big of tires will the Big Fat Dummy Run? Apparently, Surly went straight for the biggest, baddest tire that doesn’t even exist yet – a gargantuan 26 x 5.25″. That’s almost another whole tire more than the stock 26 x 3.8″ Nate.
The reason for the smaller tire spec is that in order to fit bigger tires, you run into some drivetrain limitations. Fitting a 197mm thru axle fat bike hub in a frame with 5″ tires and still clearing the tire with the tandem length chain while maintaining Q-factor turns out to be pretty tricky. But they figured it out. For the complete breakdown on every possible configuration, consult the chart above or check out the post on Surly’s Blog. The short of it is that the bike comes stock with wide Q-Factor cranks and 3.8″ tires on 80mm rims to allow for a 2×11 drivetrain – since low gearing is appreciated when pedaling up to 400 lbs (total weight limit including rider and bike). If you want to run bigger tires you’re gonna have to run a 1x drivetrain or lose some of the inboard gears on your cassette, but there are a lot of options to suit your needs. It’s like a ‘choose your own adventure’ book of booze-fueled trips to the grocery store. Surly also added new cast dropouts that run a thru axle, but are slotted to allow the wheel to drop out of the frame without removing the thru axle – this is to make wheel changes easier when fully loaded with bags since they interfere with the axle being removed.
Other important changes include updated geometry with a slacker head tube angle to make plowing into things a little less abusive. Riding a fully loaded extended wheelbase bike apparently makes it hard to lift the front end, so the slacker head tube and the ability to run a 100mm suspension fork in the 44mm head tube should help. The frame is also internal dropper post capable should you choose to go that route.
The Big Fat Dummy retains all of its cargo ability, though a few things did change. Namely, the top Xtracycle deck which had to be widened to fit the frame. The Dummy Rails and bags will still work, but Surly says the width and the Dual Wideloader mounts have changed so accessories at those to spots will not fit.
With a claimed weight of 54 lbs, 4oz, the 4130 Chromoly frame and complete build kit adds on 5lb 12oz to the original Big Dummy. Availability is estimated for April/May, and price is TBD.