DIY fatbike fenders

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In an afternoon, some donated corruplast signage from Bike wRider, fender hardware spanning several decades from Off The Chain bike co-op in Anchorage, and several dollars of aluminum door threshold sourced from the hardware store become a fatbike fender.  The whole thing was assembled with a Crank Brothers multitool, some standard M5 nuts and bolts, and the leather punch on a Swiss-Army knife.  The aluminum threshold material is extremely lightweight and bends easily, while retaining enough rigidity in use.  The corruplast has proven its durability all summer, despite a variety of abuse.  It is best to align the corruplast “with the grain”, as it will bend and crimp in the opposite direction.  The modified Nitto M18 rack is integrated into the design, and the steel tang shown below was eventually removed as the aluminum fender rib served the same purpose.  I did not expect the fenders to last through the entire summer, but they show no signs of letting up.  Eventually, I made a front mudflap from duct tape and reflective ribbon, and the rear mudflap was sourced from a broken Planet Bike fender.  DIY fatbike fenders– Take America Back!

First, bend the aluminum and locate the holes.  Drill, and install to the frame.  It is nice that the Surly Pugsley has proper threaded fender mounts on the inside of the seatstay and chainstay bridges, despite few commercially available fenders in this size.

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At first, the flat steel rack mount was used, but was later removed as it was redundant.

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Locate the holes to bolt the rack to the frame of the fender.  The Nitto rack is made of tubular Cro-Mo, while the struts are solid aluminum with steel hardware.  I removed the backstop support of the rack, simply by bending and breaking it  The sharp fragments of brass filler are covered by the red electrical tape.  In the future I might do all of this differently, although with the knowledge that it has lasted all summer I cannot complain.  This was my final project before leaving Anchorage this spring.  While a but crude, I wasn’t going to let the planning phase encroach on the ride.

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Clearance is a little tight with the modern top-pull front derailleur.  A little bending will do.

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In addition to the Nitto Rack stays, a chromed steel fender stay from an old ballon-tire bike was used.  Made of low-grade steel, it was easy to widen and bend to shape.

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After installing the aluminum and mounting all the bolts, I removed all the parts and reinstalled with the corruplast.  There is excessive clearance for the 60mm tire, but the design is intended to fit a full-sized fat tire.

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A Carradice saddlebag typically mounts to the seatpost, but with a bag support I find I can fit several drybags between the the bag and the seatpost.  Aside from extra capacity, this method reduces swaying common with saddlebags, and provides some cushion to my MacBook which is stored vertically in the Carradice Camper.  A basic nylon gear strap holds thing in place.

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Ideally, the corruplast is used in the other direction, “with the grain”.  It does work in this orientation, but it tends to bend into a ridged shape like corrugated cardboard.

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This direction gives a clean bend and holds a nice shape.

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60mm Schwalbe Big Apple tires on 65mm rims roll well on pavement, allowing a handful of hundred mile days.  On dirt and gravel roads, traction is a bit scant.  I might select something with a little more tread next time, even if only the Schwalbe Fat Frank tire.  For a more aggressive tread in this tire size, there is the Maxxis Holy Roller 2.4″, Kenda K-Rad 2.5″ and the Kenda Slant Six 2.5″.  There are other options with considerably more aggressive tread patterns for downhill use, but they also approach the weight of a proper 4″ fat tire.  The Big Apple is a little lighter than the smooth Black Floyd tires available from Surly, and as I expected, are quite durable and puncture-resistant.  I didn’t have a single flat from Anchorage all the way to Bozeman, Montana.  When I fit fat tires, I sent the Big Apples back to Anchorage where Bike wRider intends to finish them off.

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I like a bike with fenders and powerful dynamo lighting.  The Pugsley has been my daily transportation for almost a year, and these features make it comfortable and safe in all conditions.  I have little time on the Pusgley without the fender, except in a frozen Alaskan winter when it is unnecessary, but one of Joe’s considerations after touring on the Pugsley in the summer of 2010 was that a fender would combat the “unusual amount of spray in the wet”.  I still experience some overspray onto my feet while riding fast in extremely wet conditions, such as on pavement.  Overall, I remain clean and dry.

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The Take America Back slogan was part of Joe Miller’s unsuccessful bid for Senate in 2010.  He was a vocal Tea Party candidate, but lost to Republican incumbent Lisa Murkowski, a write-in candidate in the race.

FreeSpoke; Surly Marge Lite to Shimano FH-M475, for Pugsley

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The rim and tires came in the mail from Surly and the hub was sourced from The Garage in Helena, MT; the spokes were cut at the Summit Bike Shop in Bozeman and a truing stand was arranged via Craigslist.  FreeSpoke provides the spoke length calculation and the graphic assurance that I have put all my pluses and minuses in the right place.

Rim: Surly Marge Lite

ERD: 543.5mm

Spoke bed offset: -6mm, +6mm

Hub: Shimano FH-M475

Center-to-flange: L 33.5mm, R 20.5mm

Flange circle diameter: 61mm, both sides

Spoke hole diameter: 2.5mm

Hub offset: 17.5mm

Spokes: 32

Lacing pattern: 3 cross

Left Right
Spoke length 261.3mm 262.3mm
Bracing angle 4.8°
Tension distribution 100% 69%
Spoke head clearance 2.61 mm 2.61 mm

FreeSpoke is my preferred spoke calculator.  The graphic description helps ensure you’ve input all the proper dimensions, especially when offset hubs and rims are involved such as with the Pugsley.  The above calculation is for a Surly Marge Lite rim built to a Shimano FH-M475 rear hub, for Surly Pugsley.  The dimensions of the Deore and XT high-flange models appear to be the same as the M475.

For this build I used 262mm spokes all around.  Some Rock-n-Roll Nipple Cream was applied to the threads, while the spoke holes and nipples were generously greased to prevent corrosion in use and to reduce friction during tensioning.  This is the first time I’ve used a commercial spoke prep. Linseed oil is messy, and does too little to minimize friction and wind-up during tensioning in my experience.  The Rock-N-Roll prep is less messy than linseed oil and was easier to work with during the build.  I’ve had success building wheels with standard bearing grease, and wouldn’t hesitate to do it again.  With proper spoke tension, I’ve never had any spokes loosen in use.

In a day, I sourced all the necessary parts, laced the spokes, tensioned and dished the wheel, and installed a new pair of lightweight Surly Larry 120tpi tires.  In a day, the metamorphosis is complete– my wheels are lighter, yet more voluminous than they were yesterday.

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My rear Schwalbe Big Apple developed a slow leak in the last two days of use, and a shred of steel was found when the tire change took place.  Technically, I managed to ride from Anchorage, AK to Bozeman, MT without a flat, a distance of over 3200 miles.  To dish the new wheel properly, I installed it in the frame several times and used my fingers to estimate the distance from the chain stays.  About 2000 miles since Whitehorse, my second chain on this cassette is worn.  The time has come to return to 8 speed equipment, easier shifting and cheaper parts.  Check the manufacture date on the Marge Lite rim– it’s Cinqo de Mayo.

Image, calculated figures and format courtesy of FreeSpoke.

Little guns

I might ride this, although it changes every day. Large Marge and Marge Lite with Holy Rollers for now. I wish I had some Schwalbe Fat Franks or Big Apples in 26 x 2.35. The creme colored Franks are nice.  If I roll on 559-65mm rims, all I need are two fat tires to be riding full fat again.  Holy Roller, Big Apples, Fat Franks– baby fat.

For now, road levers paired to Avid BB7 Mountain calipers work fine and offer powerful braking with featherlight one-finger operation.  Stopping power is exceptional although the feel is unfamiliar.  The cable pull is improperly matched and the levers feel squishy.  I’ll experiment with some V-brake compatible road levers soon.

From full fat to half-fat, then baby fat. I call it Little Guns. One of you knows a bike that has had the same name, but that bike has since passed on.