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Bike Hacking (aka "Bicycle Autopsy") - Section 1

Section 1   | Section 2   |   Section 3   |   Section 4

One person's junk, is another person's treasures.


Over the last 150 years, the bicycle has evolved from the clunky wooden ďvelocepedeĒ to the fast, lightweight, high-tech machine of today, but the general geometry and design have remained the same with very little change. The frame geometry is still made of two triangles with the rider placed above the center of the frame. This design is very strong, gives the rider a safe vantage point in traffic, and offers an easy way to bail from the bike in an emergency. Although the bike projects presented on this compilation are completely radical and off-the-wall, many of them, including the custom frame choppers actually follow the same basic triangle frame.

Taking a complete bike apart right down to the frame is not very difficult, and requires only basic tools. In this section, we will be taking apart a common mountain bike, as shown in Photo 1, down to the frame. Although there are hundreds of different sizes and standards for bicycles and their components, the basic disassembly procedure is fairly common. 

Photo 1 - A typical bicycle.

However, before you start breaking down a bike, it is a good idea to get to know the names of the various bits and pieces, so when you have to ask for something at a bike shop, you will know exactly what to ask for, and when I tell you to chop out the head tube, you will know where to aim your hacksaw.

In reference to Photo 1, each part of the bike has a name:

A) Tires. Some common sizes are 20, 24, 26 and 28 inches.
B) Rims. Come in a range of diameters and widths.
C) Valve Stem. A one-way valve to fill the tube with air.
D) Dropouts. Holds the hub in place by tightening a nut on the axel.
E) Freewheel/Rear Sprocket. A single or cluster of gears to drive the rear wheel.
F) Rear Derailleur. Allows the changing of the rear gears by moving the chain.
G) Seat stay. Part of the rear frame from the seat to the rear wheel.
H) Chain. These come in various widths depending on the usage.
I) Chain Stay. Part of the frame from the crank set to the rear wheel. 
J) Brakes. Stops the wheel due to friction by clamping a shoe against the rim.
K) Seat. Connected to the adjustable seat post which is held in place by a clamp.
L) Seat Post. Can be adjusted up and down and locked in place by a clamp.
M) Seat Tube. Part of the frame between the seat and the crank set.
N) Front Derailleur. Allows the changing of the front gears by moving the chain.
O) Crank Set. The combination of front sprockets, crank arms and axel.
P) Pedals. Transfer power from your legs into the crank set.
Q) Top Tube. Part of the frame between the forks and the seat.
R) Down Tube. Part of the frame between the forks and the crank set.
S) Brake Levers. Transfers force to the brakes through a cable system.
T) Handle Bar. Steering system of the bicycle. Brakes and shifters are mounted here.
U) Gear Shifters. Transfers motion to the derailleur allowing the changing of gears.
V) Gooseneck. Connects the handlebar to the forks. Allows for height adjustment.
W) Head Tube. Joins the top tube, down tube, and contains the fork and bearing.
X) Forks. Connects to the head tube and holds the front wheel to allow steering.

If you are going to be fixing or building bikes as a hobby, it is a good idea to understand how everything all works and fits together. Find a complete working bike and study how each part works with the others. Turn the bike upside down, turn the cranks, and watch how the derailleur moves the chain up or down the cluster as you shift. Turn any adjusting screws and see how the adjustments affect the way things work. Just experiment with the bike and learn how it works by operating it. The best way to learn is to jump right in and give it a try.

There is really no reason to take the smaller pieces like brakes and derailleurs apart because very little inside can be fixed or adjusted anyway.

If a brake arm is bent or a derailleur wheel is cracked, just toss it out and find another one ó you wonít be working with really expensive components here.
A common problem with older bikes is bad cables. Weather causes many cables to become seized or rusted, and these need to be cut off and tossed out. When you get a bike for parts, try the shifters and breaks to see if they move. If they seem to be seized up solidly, then cut all the cables with a good pair of wire or bolt cutters and toss them away.

In Photo 2, you can see the four main cabled components; front brake, rear brake, front derailleur and rear derailleur. It is a good idea to get familiar with the proper workings of these devices, as they are essential for most bike projects. Itís not a good idea to test drive your first low racer without brakes. Trust me, I know from experience!

Photo 2 - Brakes and derailleurs.

You will find that the smaller details, such as cables, shifters and brake levers (Photo 3), and derailleur alignment and brake pads take a lot of time and effort to get right. Try to avoid cutting corners, especially with brakes. Out of a dozen old scrap bikes there may only be one usable brake, so know what to look for.

Photo 3 - Shifter and brake lever.

If you find yourself short on good cables, any bike store can cut you off a length for a few dollars, or you can buy pre-cut lengths at most hardware stores that also sell bikes or bike parts.

Another good bike building skill is to know your bearings and threads. On a typical bike there will be ball bearings in almost any part that moves (Photo 4). The forks require two, the cranks require two, each pedal requires two, the rear wheel has four sets, and the front wheel has two. Each bearing set has a cup or race that it rides in, and many of these are threaded in place to another part or the frame. These threaded parts will be both left-handed and right-handed threads.

It is really tough to remove the right side bottom bracket cup if you are trying to unscrew it in the wrong direction. As you pull a bike apart, really take a good look at which way all the parts come out, and take note of thread size and direction. You will save yourself a lot of time and broken tools by knowing how to remove a part with the least amount of force.

Photo 4 - Anatomy of a one-piece crank set.

Bearings only fit into the cup in one direction as well, so watch carefully as they are lifted out. Generally, a bearing set has a flat side, and a balls side. The balls side goes into the cup. If you do get it backwards, itís fairly easy to tell as you will get a lot of resistance from friction or a scratchy sound as metal grinds on metal. When you have removed a part with bearings, try putting them in backwards and see how they work. Chances are they wonít work properly.

The fork set bearings (Photo 5) come in many sizes depending on the bike, so you may want to put a twist tie around matching sets. The difference in size is so small that it is hard to find the right size you need if all your bearings are thrown in a large pail. If you put too small a bearing into a cup, it will not work and will be damaged.

Another feature to notice about the fork bearings is that the lower cup may be a little deeper than the top. This is because most of the weight is pushing down on this set during normal riding, so it needs to be a little heavier. The actual bearings are the same size.

Photo 5 - Forkset and bearings.

Also, BMX head tubes are normally heavier than regular bikes, so the bearing cups from the two are not usually interchangeable. A head tube cup should fit snugly in place. If there is excessive slope, the bike may start to wobble and shake when moving at high speed. A good fit requires a hammer to bang it in place, but if the cup is too big, it will not fit.

Once you have taken apart a few bikes and have a collection of parts to work with, you will notice that many parts can be interchanged between different bikes. You can swap chain rings, forks, handle bars, and create some interesting hybrids without even cutting or welding the frame. A speed bike with massive knobby tires? A small BMX bike with 36 gears capable of high speed? Sure, why not? Anything is possible.

Donít be afraid to grab your toolbox and dig right in. This is a great hobby and is easy to learn. Although many of the bike projects in this book can ride remarkably fast or are designed mainly to look cool, no special skills or knowledge beyond the basics were needed to make them from a pile of scrap bikes. If you wanted to take bike building to the extreme and learn to spoke your own wheels or drill and thread your own hubs, thatís great, but none of that type of skill will be necessary for any of the projects presented here.

Ok, now that you can talk the talk, letís pull it all apart and make a big mess on the workshop floor. The best place to begin is by taking off the wheels so you can work with a smaller package up on your workbench. Grab an adjustable wrench and begin by loosening the rear nuts in the counter-clockwise direction five or six turns, as seen in Photo 6.

Photo 6 - Removing the rear wheel nuts

If there is a lot of rust on the axel, you may need to use two wrenches, one on each side so the entire axel doesnít spin around, as this will destroy the threads. If this is the case, then make sure the wrench is tight or use a socket set to avoid stripping the nut. If the nut is already stripped or worn round, you will have to use a vice-grip, or pipe wrench to get it loose. When using vice-grips, try to avoid crushing the threads or you will be only making the problem worse.

Once you have the two rear axel nuts loose, pull back on the derailleur, so the wheel can just drop out. Depending on the tire size, you may also need to either let out some of the air or loosen the rear brake cable, so the tire can squeeze between the brake shoes (Photo 7).

Photo 7 - Aligning the elbows before welding.

Mountain bikes with fat knobby tires will have this problem, but usually letting out some of the air is enough to allow the wheel to come out with little force. Removing the front wheel is even easier ó just loosen the two nuts, and it will drop right out. Some front wheels have special washers that hook into the forks, so you may need to loosen the nuts a fair distance in order to get them to come loose from the slots. These special washers keep your front wheel from falling out in case the nuts become loose while riding.
Now that you have the wheels off, you can work on the bike atop your workbench, since it takes up less space now and wonít roll right off. If you are planning to strip the bike right down to the bare frame, this is a good time to remove the chain. This will allow the derailleurs to be removed without taking them apart.

The best way to remove the chain is with a chain link tool. This can usually be purchased for under $20 from any bike store and will last a lifetime. Place the tool on a link and turn the crank as shown in Photo 8. The link will pop out with little fuss. Doing this procedure with a hammer and punch is not only frustrating and slow, but can sometimes damage the link or your finger when you miss. If you do decide to do it the hard way, put a small nut under one of the link pins, then bang the top with a hammer until it is flush with the link. Now take a small punch or nail and bang the pin until it is almost all the way out so you can separate the links.

Photo 8 - Chain link tool in use.

Once the link is open, pull the chain through both derailleurs and set it aside. If the chain is very rusty, you can try soaking it in a can of Varsol, or oil, but if it seems too far gone, donít waste your time, throw it away. After soaking for a few days, the links should move easily.

Now itís time to get rid of the small stuff, brakes, derailleurs and cables. At this point, you should decide if you want to keep the cables or just cut them right off. Many bikes found in scrap piles or yard sales may be rusty and seized, so cutting cables with side cutters may be a lot faster than removing them the ďniceĒ way. Try the brakes and shifters. If they donít seem to move at all, just chop them off and send them to the garbage heap. If they seem like they may still be useful, then letís start removing all the cable ends from brakes and derailleurs.

Brake cables are usually held on by a hollow bolt that crushes the cable against the brake arm. To remove the cable, loosen the nut until you can pull the cable right through the hole (Photo 9). If there is a small cap crimped to the very end of the cable, pull it off with pliers. This is used to stop the cable from fraying, and cannot be put back on later. Also, be careful with frayed cables because they can cut you easily if they are pulled with bare hands. Wearing a pair of work gloves is a good idea here. 

Once you have both brake cables out, pull out all the cables so they are only connected right at the brake levers. Cables may be routed through holes or knobs in the frame, and it may be necessary to pull the sheaths right off the cables in order to get them all the way out of the frame. Once you have the brake cables done, do the same for the front and rear derailleurs, as shown in Photo 9. Start by loosening the nuts that hold the cable ends and pull them all out right back to the handle bar or frame mounted shifters.

Photo 9 - Removing the brake cables.

In Photo 10, you can see the small cap that is crimped on the cable end. This should easily pull of with a pair of pliers and is of no use once removed. There should be no cable attached to the bike except for at the shifters and brake levers mounted on the handle bars. 

Photo 10 - Cable ends are capped off.

Now is a good time to remove the handle bars, so that all of the stray cables are out of the way. The fastest way to get them off is by removing the gooseneck rather than all the levers and grips. It all comes off by loosening one bolt ó the one in the middle of the neck. This may be a standard bolt, or require a hex key wrench (see Photo 11). Either way, find the size you need and turn the bolt counter-clockwise about 10 or 15 turns.

Section 1   | Section 2   |   Section 3   |   Section 4


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