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mz skillbldr april bike 600x80 Skill Builder: Basic Bike Teardown

RadBrad and KoolKat, of Atomic Zombie, wrote this wonderful guide to the fine art of bicycle deconstruction. You can learn a lot about a machine by stripping it down to its constituent parts. And in this case, you end up with a lot of parts that you can combine with other parts to fab your own Frankenbike. Here’s an excerpt from the piece, a bike breakdown anatomy. The entire piece can be found on Make: Projects. – Gareth

biketeardown Skill Builder: Basic Bike Teardown
OK, now grab your toolbox, and let’s tear this bicycle down to the individual parts.

Starting with the front of the bicycle, the above figure shows the parts that you should get to know by name. As per the letters, the components are:

A) Handlebars, gooseneck, brake levers and shifters. Handlebars are held in place by the clamp on the gooseneck and are available in many widths and heights. Often, a mountain bicycle will have straight or slightly curved handlebars such as these ones, whereas a road bike will have “curly” handlebars which allow the rider to hold on in two positions – a relaxed upper position, and a more aerodynamic “tuck” position. The gooseneck fits into the forks stem, and is held there by a wedge, which will be shown in greater detail later on. Goosenecks are available with two common stem diameters, so make sure you don’t put the smaller sized gooseneck into the larger sized fork stem, or it will not be completely secured.

B) Head tube and fork stem. The head tube is the part of the frame that the fork stem is inserted into. The two cups on the top and bottom of the head tube carry the fork bearings, and will be shown in greater detail later. Head tubes are available in two common diameters, which means that there are also two common sizes of head tube cups and bearings. Again, always ensure that the parts are the same size, or there will be excessive friction in the steering system. There is no common standard for the length of the head tube, or the length of the fork stem, so you should keep matching parts together as a set as you collect them.

C) Front forks. Front forks come in a vast array of sizes, shapes and styles, ranging from the most basic straight leg style to the ultra heavy duty triple tree motocross style forks used for downhill mountain bikes. The front forks will fit only one size of front wheel properly, and the most common sizes for the bicycles you will be working with are; 26 inch, 24 inch, and 20 inch. Most modern front forks will also include the front brake mounting hardware such as the one shown above.

D) Front brakes. The front brakes are the most important brakes on most bicycles, as they do the most work. Modern bicycles have cantilever brakes installed on the front forks, but you may also find some brakes that connect to the front forks using a single bolt through the crown of the fork. The type of brakes that connect to the fork using a single bolt are caliper style brakes, which are much less effective than the cantilever style shown in the figure due to the fact that they do not exert as much friction on the front rim.

E) Front wheel. Bicycle rims are available in many sizes and styles, but the 26-inch rim with 36 spokes is by far the most common wheel for an adult sized bicycle. Extremely cheap rims are made of steel, do not have stainless steel spokes and should be avoided due to poor braking characteristics and strength. 20-inch diameter wheels are often used for children’s bicycles and freestyle BMX bikes, and they can have as few as 26 spokes and as many as 48. BMX wheels with 48 spokes are extremely strong, which is why they are often chosen for trikes or load carrying cycles.

F) Front hub. The front hub will have spoke hole drillings to match the rim, with 26 holes being the most common number of spokes for an adult bicycle. Decent quality hubs are usually made of aluminum, but you will most likely find both steel and aluminum hubs in your scrap pile. The hubs contain a pair of ball bearings to allow the hub to spin with minimal friction around the axle.

G) Front dropouts. The front dropouts are slotted tabs on the front forks that allow the front axle to drop out of the forks once the nuts are loosened. Unlike the rear dropouts, the hole is not slotted, so it is not used to adjust the wheels position in the forks. There is usually a small hole above the axle slot where a special tabbed washer can help lock the front wheel in place in case one of the axle nuts comes loose.

H) Top tube. The top tube runs from the head tube to the seat tube and is normally under compressive load on a bicycle frame. The top tube is usually the second largest diameter tube in a bicycle frame.

I) Down tube. This tube runs from the head tube to the bottom bracket and is under tensile stress in a bicycle frame. This is normally the larges tube in a bicycle frame, and one of the most important in the strength of the frame.

J) Seat tube. This tube is normally the same diameter on all bicycle frames as it has to carry the seat post, which fits snug inside the tube. The top of this tube will also have some type of clamp which will tighten around the seat post, allowing it to lock in place at the desired height. On a suspension bike frame, this tube may or may not have the duty of carrying the seat post. On the frame shown above, it does not.

Bike Teardown (on Make: Projects)

More:
See all of our Bikeshop Skill Builder series

Gareth Branwyn

Gareth Branwyn is a freelancer writer and the former Editorial Director of Maker Media. He is the author or editor of a dozen books on technology, DIY, and geek culture, including the first book about the web (Mosaic Quick Tour) and the Absolute Beginner’s Guide to Building Robots. He is currently working on a best-of collection of his writing, called Borg Like Me.


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