My first major build — The Chupacabra Custom Chopper

These steps chronicle the process of my first major custom bike build.  I say “major” because it was the first project of mine that involved welding.  I attempted to learn how to weld as I went along, so you’ll have to cut me some slack on how ugly the welds look.  🙂

This bike build was started in February 2014 and completed in April of 2014. The steps follow below, but first a couple Thank you’s…

Start with a 15″ automobile rim and tire

I began this chopper build by starting with the rear tire (picked up for free from the “Free” section of As you will see I then built the bike’s frame around the tire. This chopper uses a 15″ automobile tire as its rear tire. A 15″ automobile rim is the same size as a 20″ bicycle rim — something that will prove useful when building (i.e. lacing) the chopper’s rear wheel.


Drill, drill, drill

After removing the insert from the wheel spoke holes were drilled. [Hint: Use a 20″ bicycle rim as your template for the placement of the holes.] [Another hint: Have extra drill bits on hand.]


Fabricating the rear hub

Making the hub for the rear wheel. A steel rear hub is cut into halves to make the new hub for the chopper’s rear wheel. The hub must be made of steel in order to weld it. Hint: use a magnet to determine whether the hub is made of steel or aluminum. Then drill additional spoke holes on the flanges to match the number on side of the rim. In my case I doubled the original number of holes.


Elongating the axle

If you don’t have a long piece of threaded axel rod laying about, you can create your own by cutting in half the stock axel and then adding (welding) a piece of rod to create the desired length. Hint: I used a piece of angle iron to clamp the pieces to in order to insure alignment when welding.


Super-wide rear hub

Extend the width between the flanges by welding a piece of pipe the desired length. Then repack the bearings and reassemble the new elongated hub using the extended axel. This photo shows the difference in length between a stock rear hub and the extended one.


The wheel with tire mounted

With the tire mounted, the rear wheel is now complete. Now the frame building can begin. I must say, the build of the rear wheel takes a bit of time, but it is well worth it. [After the forks] The rear wheel is the focal point of the chopper. Spend the time on this one component and you will be incentivized for the remainder of the bike build.


The sacrificial bike

Obtain a bike (or bikes) from which you will salvage the additional parts needed. I chose this Schwinn O.C.C. Stingray Chopper Jr. for the sacrificial bike. This poor little bike will be chopped and parted out for my Chupacabra build. The rear dropouts will be cut out and utilized on the new frame. As will the bottom bracket. The triple-tree front fork parts will be utilized and extended. The handle bars will be utilized and extended. The head tube, the seat, rear fender, and anything else that I can salvage will be also be repurposed.

[Note: The rear wheel of this bike was used in a subsequent bike mod. See Lowered Adult-Sized TricycleEd.] [Here’s what remains of this bike today: The sacrificial bike – redux.]


Homemade jackshaft

Because of the width of the rear wheel, the rear sprocket was offset very far from the chainring creating an alignment issue.  Therefore a jackshaft was needed in order to transfer power from the chain ring to the rear hub.

I fabricated this jackshaft using the freewheel sides of two rear hubs.


Atomic Zombie rocks!

Again I’d like to thank for providing the plans, tips, techniques, design advice, and confidence that allowed me to build this bike. Their webisite has several plans for download; including plans for the “OverKill Phat Ass Extreme Chopper” — on which Chupacabra was built. They also have a book, Bicycle Builder’s Bonanza, which I recommend. Tips ranging from where and how to salvage bike parts to planning and designing your bike project.

Bicycle Builders Bonanza