I Made a Fatbike

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With flu season swiftly approaching, I find myself suffering from a different kind of fever: FATBIKE FEVER.  For those of you unaware, fatbikes are a new trend in the cycling world, catching the attention of mountain bikers, winter commutersadventure cyclists, and outdoorsmen.  Fatbikes, such as those offered by Surly and Salsa, are regular bikes with massive tires ranging from 3 to 5 inches wide.  They’re like the Hummers of bikes, rolling over almost any terrain: sand, snow, tree roots, gravel, cinderblocks, and probably even small children.  I’ve had the privilege of poking fun of my good friend for commuting on his hog of a bike, Ugbeast, before I started realizing how much more fun he was having with his fatbike.  Wanting to ride off the pavement and into the woods, I pulled the trigger-shifter.  I got me a fatbike.

Being a bicycle mechanic with access to plenty of tools and resources, I decided to build the bike frame-up.  After a fair amount of research, including test rides and extensive discussion with fatbike nerds at Revolution Cycles, I decided on the Surly Pugsley.  I knew that I wanted the versatility of having “traditional” 135mm hub spacing, allowing me to build wheels using more common hub sizes instead of extra-wide fatbike-specific ones.  The Pugsley allows for this with its offset frame, which basically bends all wonky in one direction to allow room for a ginormous tire. Furthermore, I was attracted to Surly’s offset fork, allowing me two rear wheels to run on my bike at the same time, ostensibly having two bikes in one.  (In other words, I can easily switch between a geared bike and, in my case, a single speed without having to rebuild or re-dish my wheels. This can come in handy if my freehub body freezes up when I’m in the middle of nowhere; my backup wheel is on the front of my bike!)  Finally, I’ve had great experiences with Surly products and wanted to support a solid company that builds solid steel frames.  With friends and fatbike fellows urging on the Pugsley, it seemed like the best choice for my price range.

Without further ado, let’s get into the build!  I enjoy documenting various projects of mine, and so here’s a foray into bike-building for the curious:

Step 1: Frame Saver that sucker!  If you’re building a steel bike, it’s always a good idea to apply a protective coating of rust inhibitor inside of the frame before adding components.  Surly recommends this with all of their bikes, as it prolongs the life of your investment.  Frame Saver is an excellent product for such things, and there are several similar products out there.  Over the course of 48 hours, I applied two coats by spraying it in all of the frame and fork’s openings, plugging up the holes, and rotating the frame with the liquid inside to spread it evenly.  When it dries, it reminds me of a thick layer of ear wax.  Yup, gross.

WP_20141008_002As my frame was being Frame-Saved, I built up my two wheels.  It’s been a couple of years since I built a wheel from scratch, so I needed to reacquaint myself with the process via Sheldon Brown’s fantastic tutorial.  Having never built fatbike wheels, I had to do some learnin’ on that as well, finding useful resources via Surly’s website.  Using Quality Bicycle Product‘s Surly corrections chart for offset wheel building, as well as their spoke calculator, I determined the spoke lengths needed for both wheels.  Here’s what the spoke-cutting device looks like:

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I used DT Champion spokes, which are double-butted.  Double-butted means that spoke gauge is thicker at the ends and thinner in the middle, allowing more strength at stress points, more elasticity in the middle to disperse to neighboring spokes, and a little bit of weight saved.  I used a 3-cross lacing pattern, which is generally considered the strongest with the least amount of stress.  My REAR rear wheel was built with a 9-speed Shimano XT hub, my FRONT rear wheel a Surly single-speed New Hub.

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Surly’s Pugsley frame comes with a special adapter to use when dishing the wheel (i.e., centering the rim within the frame).  You can see the red cylindrical adapter pictured above (not my water bottle).  The adapter is attached to the non-drive side of the hub when the wheel’s in the truing stand or being measured with a dishing tool.  Note the red adapter in the picture below, as well.

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Another peculiar thing about fatbike rims (in my case, the 65mm-wide Surly Marge Lites) is that they have 64 spoke holes drilled into them.  Most hubs have 32 holes.  Half of the spoke holes on these rims are not used!  When building rear wheels for an offset frame, you use only one of two lines of spoke holes, as the rim is pretty off-center compared to the hub.  You can visualize this here as you can’t quite see it in the picture above.  If you were building a symmetrical rim for a front wheel (which I did not), you would alternate between the two lines of spoke holes.  Next time you’re near a fatbike, check out the wheels.  Mind-blowing!  (At least it was for me when I learned about offset stuff….)

The Surly Marge Lite rims that I built up were pretty beefy, and the welds were a bit sloppy.  I am used to building up more precision rims, but the internet told me not to fear; fatbike wheels need not be precise.  I brought the wheels up to tension while dishing and truing them, although the perfectionist in me was a bit peeved at the condition of my radial truing with respect to sloppy welds.  As far as tension goes, without a tensionometer at hand, I did ’em by “feel,” which I double-checked with an expert wheel-builder the following day.  I was in good shape.

Then came the Moment of Truth: testing the wheel in the offset fork, making sure the rim was centered.  *holding breath*  …  It worked!  I did it!  My first fatbike wheelset build!

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Now for the rest of the build!  I set aside an entire day for the project, feverishly building, forcing myself to take food breaks amid the mania.  (It’s more difficult than you think when you’re in the zone.)  After cleaning spilled Frame-Saver-ear-wax off the frame, my first step was fork installation.  I don’t get to do these too often, and they use neat specialty tools, so it was a lovely start to the day.

Installing a fork means installing a headset with it.  The headset contains the bearings by which the steering works.  First, I had to install onto my fork the crown race, a smooth, curved ring upon which the bearings sit.  This is my favorite to install, as it involves a lot of banging to force the little ring on.  Here’s a pic of the tool with its various attachments for various crown race sizes:

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Next, you install similarly curved ring bits to the frame.  These are called headset cups.  A clamping tool called a headset press is used to force these suckers in nice and level.  The teens I used to work with called this tool “The Helicopter”:

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Loosely assembling all components, I measured where I wanted to trim the fork’s steerer tube so that I didn’t have to use inches of extra spacers with my headset installation.  In other words, the fork’s “handle” was way too long for my small frame, and I wanted to make it shorter.  Some people hold off on cutting until after they’ve ridden the bike several times.  I had a good idea of where I wanted things based on my current commuter mountain bike, so I decided to cut the tube down first, with a few inches of wiggle room.  I used a special clamp, a vice, a hack saw, and a lot of cutting oil:

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After filing down the freshly cut steerer tube, I installed the fork, the stem (where the handlebars attach), and the rest of the headset components, tightening it all down just right.  And, in the stem’s case, to spec using a torque wrench set to 5nm.

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I moved next to the bottom bracket area.  The bottom bracket contains another set of bearings, this time allowing the pedal arms (crankset) to swing around.  I installed a cartridge-style square-taper bottom bracket I purchased from Rev.  The Pugsley frame takes a longer-than-normal 110mm bottom bracket.  To the bottom bracket, I attached a set of used Bontrager mountain cranks that fit the 104 BCD (Bolt Circle Diameter) chainring I purchased.

Let me tell you about that chainring!  Another interesting thing I learned when selecting my componentry is that, for mountainbikers who want a single chainring up front (instead of multiple gears), several companies manufacture special chainrings designed to hold onto chains over rough riding and abrupt rear gear-changing.  These “narrow wide” chainrings alternate between narrow and wide teeth throughout the ring, which grasp stronger via small differences in inner- and outer-plate linkages on the chain.  Some of these rings alternate a slight tilt in and out, as well, like stereotypical British dental profiles.  I decided on a RaceFace narrow wide chainring, not because of its “aerospace grade strength,” but because it came in orange.  A girl’s gotta have some vanity.

WP_20141011_006I needed to see the chainline once the rest of the drivetrain (cassette, derailleur, and chain) was installed before settling on where exactly the chainring ended up.  I ended up swapped the chainring to the inside of the crankarm, not the outside as pictured above.  After adding the handlebars, though, my Pugsley started to look like a bike!

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On to wheel installation!  Before adding the wheels, however, I needed to install the disc brake rotors.  These brakes operate via pads clamping down to a disc, unlike most street bikes which slow via pads grabbing hold of the rim itself.  Rotor bolts need to be tightened down in a star pattern (instead of, say, counterclockwise) to set the rotor firmly in the center of the wheel.  I learned this the hard way.

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I did this for both of my wheels, installed the cassette (rear gear cluster) onto my 9-speed rear hub, and stuck them round bits on the triangular bits!  Those are 3.8″ Surly Knard tires, by the way.

WP_20141011_010 (2)Next was brake setup.  I installed both Avid BB7 disc brake calipers onto the frame and fork, which have special attachments for disc brakes.  I ended up needing to tweak these a fair amount after some test rides.  The rear brake required extra washers to space the disc brake calipers where they needed to be.  Not pictured are the brake levers I installed on the handlebars, and the cable and housing betwixt the two.

WP_20141011_012The last components I installed were the chain, rear derailleur, and trigger shifter.  I purchased more basic 9-speed Shimano parts for these, as I realize that rear derailleurs may very well get banged around on trails and snow.  I didn’t think of taking a photo of the under-appreciated chain tool, as I use it daily.  Thank you, chain tool, and sorry I don’t acknowledge you more often.

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Let me take a moment to talk about the Surly fatbike rims and accompanying rim strips, as the photo above features such things quite prominently.  To make the massive rims lighter, Surly’s punched large holes out of the center of the rim, between those two lines of spoke holes I mentioned earlier.  This also serves a Coolness Factor, as then you can install brightly colored rim strips that pop out like little Emergency Buttons when the tire is inflated.

I accessorized my bike with more orange, go figure!  Orange grips, orange brake housing, and even some lovely orange bottle cages!  Here’s a peek at my “dashboard,” where all the action happens:

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And finally, a bike!  A FATBIKE!  My fatbike, named Dreadnoughtus!  Yes, after the recently discovered ginormous dinosaur.

bike_stuff08Now I get to ride her all over town, through woods, along streams, and down deer paths.  I’m learning to bike all over again, as singletrack is very different from asphalt.  I’m excited to get involved with the Madison’s fatbike community and get out in any weather, on any terrain!  I’ve already explored gravel on railroad tracks, banked curves on wooded trails, and sandy construction sites.  Next, the world!

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6 thoughts on “I Made a Fatbike

  1. roland roberge

    impressive and motivating …. just search on this subject and stumbled on your article..Nice!!
    thanks again for the details and picture.. will help quite a lot to decide to startup the journey towards a customized fat bike.

  2. am about to begin my own fat bike project and reading about your build helped me envision the entire process. planned to make it somewhat easier with purchase of the SRAM build kit for Fatbikes at $330 or so. brakes – am considering an elixir set from CL or the CRC Avid replacement of Elixir at $130. Nuances of your blog – like star pattern disc bolt tightening, wouldn’t have known to do that – should help me move through the process with only a few head tilts. having only graduated from the notorious Park Tool School, i feel much more confident knowing you have accomplished this as well. i don’t have the tools at my disposal, and was hoping i don’t NEED the headset press (have replaced many a headset and not needed the press), but am thankful for the images and details contained herewith.

    happy riding!

    Lenabena
    Alexandria VA

  3. Junglejay

    Great, informative write-up! Makes me want to up my home mechanic game and try wheel building… Also, nice job linking to interesting items throughout. I like your bike’s color scheme. What is your saddle? Is that an Ice Cream Truck Ops in the last picture? Cheers.

    • Tops

      Thanks for the kind words! My saddle is an ancient Terry Butterfly (yes to leopard print!). The other fatbike in the last picture is a Pugs as well.

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