Offset Double Cranks
Surly’s O.D. and MWOD offset double cranks remove the big ring from a traditional mountain triple and move the remaining inner and middle rings outboard to the middle and outside positions. Doing this allows the chain to clear the tire in the easiest gears while minimizing Q-factor (pedal stance width), and it retains the gears most useful to a bike like this, meant for crawling through loose, soft or otherwise difficult terrain.
The Moonlander employs a ‘neutral’ geometry, neither aggressive and race-oriented nor super relaxed. The resulting ride is well balanced, stable yet nimble.
Bottom bracket height drives much of a bike’s handling characteristics. The mid-range bottom bracket height on our fat bikes is designed to make them ride like ‘normal’ mountain bikes, maintaining stability while retaining a fair amount of clearance, useful when crossing obstacles in your path. A nifty frame feature is the dropped top tube, providing plenty of stand-over clearance.
Fat Forks And Interchangeable Wheels
Surly OmniTerra frames use specially bent seat- and chainstay tubes to offset the centerline of the rim from centerline of the frame, allowing chain clearance at the tire.
Surly offers both an on-center and an offset Moonlander fork. The on-center version comes stock with the frame. It features bottle cage mounts in the modern triple-boss design, meaning you can use standard or oversize cages to increase your capacity for hauling water, fuel or gear. Offset forks (available separately) match the offset of the stays. When our frames are paired with the appropriate offset fork, wheels of the same spacing and offset can be used front and rear. This can be a true lifesaver if your freehub fails in extreme conditions or remote locales.
We offer fat bike tires in many sizes and tread patterns to accommodate your terrain, riding style, performance expectations and budget. Our tires are available in 27tpi and 120tpi casings, in sizes ranging from 3” to 4.8”. Our treads vary from mostly slick designed for streets and hard conditions to aggressively knobbed versions for clawing up rocky climbs and shedding mud.
We virtually invented the modern fat bike tire, and testing of multiple generations and versions of our tires have allowed us to manufacture a tire with a casing that has the flexibility of a cross-country tire, which functions in a wide temperature and PSI operating range and is reasonably light.
Wheel Building (Non-traditional Lacing)
Offset Wheels: Our OmniTerra (fat bike) frames use unique wheels, with rims ‘dished’ out from the hub’s center. The offset matches the offset of the frame (28mm for Moonlanders and 17.5mm for Pugsleys), retaining full gear range while allowing chain clearance at the tire and allowing the use of common 135mm hubs.
Fat Rims On Regular Bikes: Depending on frame clearance, our Rabbit Hole (50mm) and Marge Lite (65mm) rims may fit on bikes other than the fat bikes they were designed for. For example, when fitted with a 2.5” tire the Rabbit Hole can work with many rigid forks and some 29er frames.
Surly rims are made of extruded 6000-series aluminum. Each rim is multi-stage heat-treated to harden it, resulting in a light but durable rim.
Each rim’s profile is unique, borrowing the low weight of a single wall with small open cavities which strengthen them for the unique rigors produced by fat bikes. Westrive to keep them light but strong.
The tire bead-hook shape and diameter make it easy to install and remove tires, while holding them firmly in place even at very low air pressure.
Our rims have two rows of spoke holes, allowing each rim to be built on-center or offset. This way, one rim can accommodate a wide variety of frames & forks, making choosing and purchasing the right rim easy.
Tire/Rim Drive-Train Compatibility
i. Surly makes a host of different frames, rims and tires and some of them can be mixed and matched the basic formula is below.
ii. Frame + Crank = Max Tire Rim
iii. Chart to be manufactured
Fork Tech: Two Forks One Bike
i. Surly offers both an offset and an on-center fork for the Moonlander. The on-center fork is considered by many to be the more aesthetic option, while the offset provides greater usability in the field in case of drivetrain failure or fun. (with the correct corresponding wheel)
ii. Triple water bottle boss forks. We offer aftermarket forks with triple water bottle bosses to ad more water bottle/cargo carrying capacity.