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Fat Bike Blog #3 - Building My Fat Bike - Fast, Light and Pretty

Friday, January 11, 2013


I took a lot of days off from work during the holidays. During my break, I demoed fat bikes. Firstly, I didn't even know if I wanted a fat bike. Secondly, I wanted to test all the available fat bikes to see if there was one that suited me.

Here is the link to my first fat bike blog.

Here is the link to my second fat bike blog.

For my riding style and tastes, there was one fat bike that was head and shoulders above the rest. The 907 was simply amazing. The 9-oh-7 blasted through deep snow, danced lightly over rocks and fallen trees, and was scary fast ripping down a winding snow packed single track!

The 907 is well designed and can take the monster "Big Fat Larry" 4.7 inch wide tires on 100mm wide rims. Here is a photo I found on a Finnish site of 907 that treks into the arctic.

The 907 comes is a variety of colors, including polished silver, which is only available in Alaska.

9:Zero:7 makes and sells bike frames, not complete bikes. Each 907 is unique and is personalized for each rider.

PART 1: Bikes are Bikes

Bikes are pretty complex machines. Here is an exploded view of the basic components of a modern bike:

Most modern pedal bikes have the same basic parts, which include:

Handlebar and Stem
Chain (sometimes a belt)
Rear Sprocket

This diagram shows the names of the various parts of a mountain bike.

This diagram maybe a little hard to read. Here is the link to moutain bike component diagram.

This link shows a typical road bike component diagram. Although mountain bikes, fat bikes, and road bikes are designed for different surfaces, the basic layout is the same. As a matter of fact, the first mountain bikes were steel road bikes with knobby tires, flat handlebars and lower gearing.

These diagrams shows that a modern bike is a pretty cool technological achievement. When you purchase a bike, all sorts of engineering wizards have been at work figuring how all the parts and pieces go together to give you the best bike for your money.

With the few exceptions, bike companies really only make bike frames. Some mega-bike companies like Giant and Specialized design their own stems, handlebars, seats and/or tires. More often than not, bike companies, like Trek, contract with a specialty firms to make branded parts.

However, even the mega-companies buy components from specialty manufacturers. For example, I bought a Specialized Stumpjumper mountain bike with wheels that consisted of Shimano hubs, DT swiss spokes, and Mavic rims. My Specialized Camber Comp came with a Shimano Alivio crank, Shimano Alivio Shifters and Shimano SLX derailleurs. The Camber has a suspension that uses a Rockshox fork and rear shock.

Many years ago when you bought a bike like a Schwinn Varsity, every part was made by Schwinn and would not interchange with, say, a Raleigh. Today, there are industry standards that allow for Interchangeability of parts. There are variations, of course. For example, seat posts come in three diameters of 27.2mm, 30.9mm and 31.6mm. The 907 requires a 30.9mm seat post. Bicycle headsets have different diameters ranging from 29.9mm to 55.95mm. Bottom brackets have a number of sizes and configurations from press fit to screw-in.

To build a bike starting with just a frame, you have to buy components that are going to fit. The good news is that manufacturers publish frame specifications that have information on the type of components that will fit.

PART 2: 907 Fat Bike Build - Frame and Fork

I selected an orange 9:Zero:7 aluminum centered frame with a 44mm head-tube and 170mm rear hub spacing.

This frame is made of ultra light heat treated 7005 aluminum alloy with hydroformed tubes. The chainstays are symmetrical and the rear wheel is centered on a 170mm "fat" hub.

Some fat bikes, such as the Surly Pugsley, use an offset fat wheel on a standard 135mm hub. The wheel is laced with the spokes on one side to provide an offset to the wheel. The chainstay on the drive side angles outward to to keep the offset rear wheel centered relative to the rider. This "offset" wheel and frame is a clever way to mount a fat rim on a narrow hub. However, chain clearance is problem and the offset wheel is not as strong as a centered wheel.

I selected the 9:Zero:7 aluminum fork.

This fork is made from heat treated 7005 aluminum alloy and is bullet proof. This fork takes 135mm hub and weighs 2.25 pounds. A fat carbon fork only shaves off 3 ounces and cost twice as much. No brainer.

I specified the frame with the 44mm head-tube rather than the 1.125" head tube. The 44mm head-tube is stronger and allows for the use of a light "Zero Stack" headset.

I selected the Crane Creek z44 headset, which has sealed bearings.

This headset is made from 6061-T6 stress relieved aluminum alloy and hardened stainless steel ball bearings. This is a very low friction headset. I hate friction!

Here is a better view of the headset parts.

From left to right in the back: lower seal, lower bearing, lower cup, upper cup, upper bearing, and top seal. The assembly in the front, includes the flange nut, top cap and flange screw. The flange nut is installed in the top tube of the front fork. The top cap sits on top of the stem. The flange screw takes play out of the front fork.

I selected the Race Face Turbine stem, seat post and handlebasr. I really liked the looks of the Race Face Turbine stem.

This stem is machined from 7075 Aluminum. Aluminum 7075 is composed of pure aluminum, magnesium, zinc, chromium and titanium. 7075 is the highest strength aluminum alloy and is used for critical aircraft parts, race cars and fat bikes! I just thought the stem was pretty. This stem weighs 3 ounces mostly because it uses six steel screws.

I decided on the Race Face Turbine aluminum handlebar rather than a more expensive carbon handlebar.

This bar is cold drawn, 7075-T6 alloy. Shot-peened for to relieve internal stress. The bars are light at 8 oz and strong. The bars are 725mm wide and fit my wide grip. The guys at the shop wanted me to go for a carbon bar. The carbon bar was way more expensive and weighed 7 ounces. Most bikes have handlebars that weight about 18 ounces!

I decided to get black ESI Chunky black grips.

These grips are silicon rubber and will help insulate my hands from the cold aluminum handlebar.

The Race Face seat post is nice because I can adjust the seat really easily. This seat post is also made from 7075-T6 alloy. The 400mm long seat post weighs 9 ounces.

The seat post is very pretty.

I have selected a very comfy seat.

This is the WTB Rocket Team Saddle with Titanium Rails.

PART 3: Fat Bike Build - Drive Train

A bicycle drivetrain consists of all the components that turn your leg power into motion, including crankset, cassette, derailleurs, chain, and shifters.

The crank I selected is the Race Face Turbine "fat" crank with a 100mm bottom bracket.

This is a very light and strong crank with forged 175mm crank arms made of 7075 aluminum. The gear ratios are 36/22T, which is specifically made fat bikes. The rings are beautifully machined from 7075 aluminum. Total weight with bottom bracket is 28 ounces.

The cassette I chose was not the super light XT cogset but the more rugged HG-81 SLX 10-speed 11/36T cogs.

I have this cassette on two of my bikes and it is excellent.

The 907 will wear the XT 10-speed chain.

The absolute coolest thing about a custom build is I get to select the shifters and derailleurs I prefer. I have selected the awesome Shimano XT group. The rear derailleur is the 10-speed XT Shadow plus.

The front derailleur is the XT e-type direct mount.

The shifters are the XT 2x10 pair.

The shifter cables are teflon coated Jagwire black carbon Ripcord..

PART 4: 907 Fat Bike Build - Wheels, Tires and Brakes

The wheels are being hand built by the Golden Bike shop on a special jig for fat bike wheels. The rims are 82mm wide Surly Holy Rolling Darryls.

The cutouts lighten the rim to 30 ounces.

The wheel hubs I selected are some of the best made for fat bikes. Good hubs lower rolling resistance and eliminate wheel wobble. Good hubs make the bike more responsive to pedal input and steering input. I bought Hope Pro 2 Evo Fat Bike Hubs.

These are simply scary good hubs. The 170mm hub lists for $266. the 135 mm front hub lists for $125.

The spokes are black DT Swiss Comps, which are light and strong.

I selected boring silver spoke nipples made of brass. Colored alloy spoke nipples are not as strong as brass.

I went with blue rim strips. The rim strips are tough plastic that show through the wheel.

I think this little splash of contrasting blue will look good with the orange frame.

The tires are the excellent Surly Nates. The only tires that the Bike Shop had in stock were the 120 TPI (Threads per Inch). The 907 I demoed had tires that were 27 TPI. Although counter-intuitive, the higher the TPI - the lighter the tire.

These 120 TPI tires are light and supple.

They gave me the 120 TPI tires at cost.

These tires are great for where I ride.

Every bike needs brakes. I selected the best bike brakes I have ever used. My fat bike will have Shimano XT IceTech brakes. The 907 I tested had these XT brakes and they rocked!

Because the bike will be used in the cold, I opted for stainless steel rotors. My 907 will have 180mm rotors front and rear.

PART 5: When WIll I Get the Bike?

The shop is still waiting on a few of the Race Face Items. I should have the bike by Wednesday, January 23rd. Building a custom fat bike takes a long time. The guys at the shop estimate my bike will be about 3 pounds lighter than the ultra-light Surly Beargrease.

Total weight will be about 27 pounds! That is light for a fat bike.

Thanks for reading my blog.
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