The original Pugsley design¶
A bigger tire could help a bike travel over snow, sand, and loose ground. It also left less room for the chain. The original Pugsley had to solve both problems: make space for a high-volume tire and a working drivetrain, while keeping a wide choice of readily available parts.
That is the design story Dave Gray tells in his May 2015 interview with Fat-Bike.com. This account follows his explanation of the original Pugsley.
Start with the tire¶
Gray says the aim was more flotation than Surly's 1×1 or Karate Monkey could offer. The larger-volume Endomorph 3.7 tire was central to that aim.
The work began with the Large Marge rim, which entered production in late 2003. With a wide rim available, Gray, Nick Sande, and Josh Yablon began developing the Pugsley and Endomorph together. Surly showed the Pugsley at Interbike in 2004, and framesets went on sale in 2005.
Make room for the chain¶
The chain runs from the chainrings at the pedals to the rear sprockets, passing beside the rear tire. A wider tire takes up more of that space. Moving the chainrings outward creates room, but the rear sprockets also need to sit in a suitable position.
Chainline describes the sideways alignment of the front chainrings and rear sprockets. Gray says getting the chain past the tire while retaining drivetrain compatibility was the biggest frame-design hurdle.
Surly chose a wide crank arrangement using a 100 mm bottom-bracket shell, the part of the frame that houses the crank bearings. For the rear of the bike, the team considered a wider hub or an offset frame using an existing mountain-bike hub.
Why the offset?¶
Offset here means placing the rear hub to the drivetrain side of the bike's centerline. That moves its sprockets outward to suit the wider crank arrangement.
According to Gray, a 17.5 mm offset gave the intended chainline with a 135 mm rear hub. The 135 mm measurement describes the hub's mounting width; the 17.5 mm measurement describes its sideways displacement. They are two different dimensions.
Choosing this arrangement let Surly use the broad selection of existing 135 mm hubs instead of developing a new wider cassette hub. Keeping familiar parts in the design was a deliberate priority.
Why match the fork?¶
Gray explains that a wide front hub also made wheel installation and removal easier. Surly used 135 mm spacing and a matching 17.5 mm offset at the fork, allowing the front and rear wheels to be interchanged.
That offered practical possibilities: a backup drivetrain if the rear hub failed, or another single-speed gearing option. Interchangeability was part of the original design's purpose, alongside tire clearance and parts availability.
Follow the sources¶
These dimensions explain the original design; they are not a specification for every later Pugsley or a parts-selection guide. Gray's interview does not establish a complete model-year history.
- Read the full Dave Gray interview for his account of the design decisions.
- Compare published frame geometry for the 2016 legacy and Gen. 2 references.
- Browse selected Surly catalogs for the frames and components listed in particular years.