Bicycles
The bicycle has been around in various forms since the early 1800’s. Today’s bicycles are based on a design introduced in England in 1885. Bicycles are a study in physical science and physics. The main distinguishing feature of a boy’s bike is the metal bar connecting the handlebars to the saddle, which bicycles for girls usually do not have. The frame style of girls’ bicycles dates to the earliest years of bicycle design, when step-through frames accommodated the long skirts and dresses that women wore in the late 19th and early 20th century.
When selecting a bicycle you will need to think about how you will be using the bicycle. No matter which bicycle you choose, you still need to think about the things you need to be safe on your bicycle. Bicycles come in many shapes and sizes and everyone should be able to find a bicycle for their needs. Bicycles can be purchased used for a few dollars or you can spend thousands of dollars on a special built bicycle for racing.
Usually the more expensive bikes are made from lightweight expensive metals, like titanium and super strength steel or they have frames made with carbon fibers. These bikes usually weight less than 18 pounds.
Bike Parts:
The frame is the main part of a bike. It is a triangular shape, is very sturdy and can be found on all bikes. The top of the seat post is very important– the seat, or saddle, that you sit on. The crank is what you make go round and round when your feet are on the pedals. The chain and the chain rings are part of the system that helps transfer the energy from you to
make the bike go forward. The fork is what the front wheel is connected to. The rim is the outermost part of the wheel where the tire is. The spokes keep the wheel round. The valve stem is the part of the tube where you attach a pump to put air in the tire. Brakes are used when you want to stop. Lastly, the reflectors on the front (white), rear (red) and in your wheels are the part of the bike that help make you more visible to others.
Saddles or Seats: Seats come in a variety of shapes and sizes. Some are springy and wide while others are hard and narrow. Some have two little pads, one for each cheek and without the front part of the saddle.
Wheels: The bigger the wheel, the faster you go and the harder it is to turn the wheel. The smaller the wheel the slower you go, making it easier to push the pedal with one revolution of your leg. In one revolution of a small wheel, you go a short distance, but it is easier. In one revolution of a large wheel you go a further distance but it’s harder to push because you are covering more ground. The smaller the wheel the closer to the ground and more stable you are. The larger the wheel the faster you will go and the higher up you will sit.
Handlebars: The handlebars are what you use to steer the bike. If adjusted correctly, you should not have to stretch too far to put your hands on the handlebars. Your elbows should be slightly bent and you should be comfortable.
Gears and Shifting: A gear is part of a bicycle that helps with speed and ease of pedaling. The more gears you have the easier ride you will have while pedaling up and down hills and in rough areas like trails. Using bicycle gears allows you to pedal with the same amount of effort whether you are riding uphill, downhill or on the flat.
Old-fashioned bicycles had the pedals attached directly to the front of wheel. The wheel would be able to make one revolution only when the bicyclist’s feet on the pedals would make one revolution. Inventors then designed a bicycle with a big front wheel so the bicyclist could go a longer distance with each pedal revolution and coast. The bigger the front wheel, the further one could go per revolution. Next, they designed a bike with the pedals connected to the rear wheel by a chain. This new design allowed the bicycle with smaller wheels to travel farther with one revolution of the pedal. Today, all bicycles have at least one gear, providing for more efficient riding.
Gearing uses basic math ratios. For bicycle gears, the ratio is the number of teeth in the front divided by the number of teeth in the rear cog that is engaged. The ratio would be front teeth:rear teeth. A larger ratio indicates the pedal requires more force to turn. So, a ratio of 40:8 is harder to turn than 30:15. So in general, the “high gear” combination of the larger ring in the front and the smaller ring in the back makes it hard to pedal. The “low gear” combination of the smaller ring in the front and the larger ring in the back makes it easier to pedal
There may be duplicate gears. If your front chain wheel has three rings and your rear cassette has eight rings, you have 24 gears. Yet, you will notice that some gears feel similar even in different combination of front and rear.
Shift Levers:
The Left shift lever controls the front derailleur and which chain ring your chain is on. It is not used as much as the rear derailleur. You will need to pay more attention when shifting with the front derailleur
The Right shifter controls the rear derailleur. This is the fine tuning of the gear range. It is used most often to adjust to minor terrain changes. Two or three shifts down is equal to one shift down on the front derailleur
Modern Front and Rear Derailleurs typically consist of a moveable chain-guide that is operated remotely by a cable attached to a shifter mounted on the down tube, handlebar stem, or handlebar. When a rider operates the lever while pedaling, the change in cable tension moves the chain-guide from side to side, "derailing" the chain onto different sprockets.
Chain Rings: Bicycles come with two or three chain rings. Three rings are for mountain biking and touring. These are low, medium, and high range or low and high for road bikes with two chain rings. The small ring is low gear for climbs, the middle ring for flat stretches and the big ring for descents. Bicycles today are available with as many as ten cogs on the rear and three chain rings up front.
Pedaling: : Pedal at about 90 revolutions per minutes both while climbing and descending. 90 rpm’s are faster than you think. Shift into an easier gear before you need it, before climbing instead of during one. You should use the same pedal force and cadence to climb as you do to descent.
Brakes: The brakes on a bicycle are the part that stops or slows the wheels. There are many types of brakes to choose from when purchasing a bicycle
Coaster brakes are a type of brake that works by pedaling backward. This is a good brake for the beginning rider or the trick rider.
Handbrakes are engaged by a grip on the handlebars that engages the brakes. There are 4 types of hand brakes:
*Caliper brake move calipers inward toward the rim. A caliper brakes moves both sides of the caliper to the rim in one motion. Never pull the front brake without the back brake to avoid a head over heels crash. They don’t work as well as others when they get wet.
*Cantilever brakes have two separate arms one on each side of the rim. Cantilever brakes require less hand force to stop the bicycle than a caliper brake. One style is called the “V” brake or Shimano brake system.
*Hydraulic Disc brakes are a closed system of hoses and reservoirs containing a special hydraulic fluid to operate the brakes. A plunger pushes fluid into the caliper where pads push on the rotor and stop the bike. Advantages: system is closed to water, dirt and debris. There is a good feel at the lever and gripping power at the wheel. Disadvantages: Disc brakes must be inspected on a regular basis. Air bubbles in the system can cause the brakes to fail.
