I've wanted to build a custom bicycle for many years. I started wondering how fat of a tire I could accommodate on a bicycle. I had seen pictures of the Hanebrink Technologies extreme terrain bicycle, but wanted something still more extreme.
The problem I considered was one of drive train alignment. With the fat tire, the chain had to shift too far outside of the normal bottom bracket to rear wheel alignment, in order to clear the tire width. I also wanted to make this work with gears, as I knew the large tire would weigh a lot.
Originally I wanted to spoke up a fat tire rim with a standard bicycle hub, but this proved impossible due the the small rim size with the large tire.
After seeing one of the most creative bike ever (see Ode to the Chupacabra on
 I got the idea of using a standard geared rear hub as a jack shaft or transfer hub between the front (bottom bracket) alignment and the rear tire alignment. This also solved the problem of gearing the bike, since I didn't have to mount the gears on the wheel itself. Thanks to The Atomic Zombie for instruction on one of his bike for the widened hub concept and for much other inspiration.
It weighs a lot, but it is a blast to ride and you never saw a bike get so much attention.
It took me a few months of noodling this around in my head and on paper before I started in earnest to create the "Fat Bastard" extreme fat tire sand bike. Hope you enjoy it as much as I do.

Let me also just say, for the record:
I did not set out to make the most efficient, or lightweight, or highest performance bike I could. It was all about maximizing tire size and working out the drivetrain issue. This was for fun! And also to learn how to weld and to see where this project might lead.


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loveoption92 years ago
Nice job on getting it all together. I have built a fat tire bike for kinetic sculpture racing. Here are some solutions that builders may find interesting. Dealing with the chain line and gearing are really a puzzle. Here is the drive system I built. It uses an 8 speed hub as a jackshaft that runs cogs on the disc brake mounts of the hub and rear wheel. It has a second gear set up as a one speed on the other side for road riding.  The 8 speed is for sand, mud and hills. I rode this at Arcata and Corvallis last year and managed to ace the sand at Arcata, and ace the course at Corvallis. I will put up an instructable about this eventually. The basic bike weighs about 50 lbs. add the water gear and it gets up to 75.  What really makes this challenging is that for effective traction in the sand, you need the rider's weight on top of the rear wheel, which makes all the chain issues even more extreme. 
marple200 (author)  loveoption92 years ago
You are correct. I've thought of all those issues and have been contemplating a new version with Nexus hub. The problem with a 10" wide tire is the pedalling clearance at the wheel, necessitating either pushing the rear tire back quite far, as in my case, or pushing the pedlas forward to get the seat (weight) over the rear tire. Also, with the extar wide tire, the hub gets pushed quite a ways outward as well. All things I have been noodling over since I built this. Nice ride. Would like to see close up photos.

amazing job there . i'm planning on doing something similar as I want to fabricate my own fatbike for beaches . for mine will be trying to make my own double width wheels by welding 2 together iditabike style . I hadnt thought of the issue of wheel rubbing against the chain but what you did with the extra chain is a clever solution .

valveman2 months ago

I like it! How is the conduit frame holding up?

LeoWorks4 months ago
simple beautiful
willnate1 year ago
make it gas powered
nez11 year ago

Thanks for sharing.

I have a Rokon, this is the eco version of it !!

I need to build this right now
Halphinian1 year ago
That looks awesome, but it looks kind of hard to pedal, so I've got a question for you: is it hard to pedal?
marple200 (author)  Halphinian1 year ago
Easy to pedal because of the 21 speeds, however, it is very heavy.
marple200 (author)  Halphinian1 year ago
Easy to pedal because of the 21 speeds, however, it is very heavy.
hobo marcus2 years ago
So cool and I just moved to NC too. I have my winter project!!! Thanx. Shhh my wife thinks its over time
I want to ride this so badly down the highway.
lambologo6 years ago
i have a moror cycle that has idenical tires to that and requires no pelataling baja mini bike
marple200 (author)  lambologo6 years ago
Several people have commented to me that all this needs is a motor. Since the purpose of the project was to make a bicycle (the pelataling kind) , that kind of defeats the objective. Some places do not allow motorized vehicles.
 Putting a motor on this would essentially amount to a Heald Super Bronc....a VERY cool MAXI (not mini!) Bike.
...or a Rokon. Crazy little things.
Rokons are badA$$ AND 2 wheel drive!! Healds were one wheel drive but still killer.
true. one with both would be relay cool. I have tryed to ride a bike on a beach and it is hard so I like the fat tires
kray9536 years ago
Agreed ;) Love finding the perfect object like that! Its one of the best feelings in DIY.
Stanley_Bob2 years ago
That is a sweet looking ride!
I Seee
Your Ride the spine link is no good it keeps redirecting me. other than that this bike is a great imaginative project
i looked, it's riding the spine, not ride.
marple200 (author)  skaar2 years ago
Holy crap!
I've had the wrong link out there for 4 years.
Thanks for picking that up.
I have corrected it now.
skaar marple2002 years ago
last triumph, turning it into a trike or 4 wheeler, 49cc bike motor added, it could be rather fun.
irvbob1232 years ago
YOU my dear friend, are a friggin genius !!!!!!!!!!!!!!!!!!!!!!!!!!
Thanks for all the tips and tricks and steps and thinking you went through with this bike!!!
I made one just like it only started with a Yamaha 7 inch fat tire dirt bike frame and disappeared the motor and transmission and welded in a Schwinn 12 speed bike frame and then proceeded to play with it until it worked. Current rendition has a 3 speed front derailer and a one speed rear. Kept the shocks and the front brake and it rides a little funny as your knees have to be out at a 45 degree angle to avoid hitting the rear shock brackets and it's one really looooooong chain with no jack-shaft like yours.
Also, I beat you, mine weighs 110 pounds! And needed two 4 inch steel threaded extensions on the crank arms to keep from hitting the rear shock brackets. Those dirt bike frames are really sturdy and seriously heavy !!!
bheldke3 years ago
it appears the bottom bracket is lower to the ground than on a regular 26" mtn bike since the rims are so much smaller and you didn't modify the basic frame design of the donar bike. Does this matter when cornering? I would imagine if you're not bunny hopping logs it wont matter.
marple200 (author)  bheldke3 years ago
Actually, the bike was constructed to obtain a normal mtn. bike BB height of around 12 1/2 - 13".
Handling in deep snow is not great due to weight of bike and geometry. Better in sand.
bheldke3 years ago
how well does it work on snow?
Maxxron3 years ago
I had trouble connecting with the Ride the Spine website, but I did find a direct link to the Chupacabra bike mentioned in the text body here http://www.ridingthespine.com/Journey/category/chupacabra. There are some amazing and innovative resolutions to design problems in both bikes.
yar19963 years ago
hey can u send me the measurements?
marple200 (author)  yar19963 years ago
Can you be more specific on what dimensions you mean?
srry bout the way i put it but is there any specific mesurments for the bike?
thirst4know3 years ago
You will be pleased to know that I thought (from your trailer vid) that you had bought this bike. Excellent work and idea.
raul carlos3 years ago
thanks for sharing your amazing bicycle with us. can we put an engine in this bicycle?
patternbill4 years ago
i want to build one of these for around town use i just need to make is hard to steal what would you suggest?
i cant think of a nicer bike thanks
Just put it next to a really nice car :D
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