Requirement 4 (C)
Requirement
Cycling
Clean and Adjust Bicycle
Using a bicycle safety checklist, clean and adjust a bicycle and present it to your counselor for inspection. Do the following:
Requirement
Show how to adjust brakes and gear shifting (derailleurs).
Brakes
Brakes are the most important components on a bicycle because they stop a bicycle in motion or help control its speed on a descent. They should function at maximum efficiency all the time. Most bicycles have either coaster brakes or hand-brake levers that control rim brakes or disc brakes. Coaster brakes should be adjusted and serviced only by a bicycle repair specialist, but you can adjust hand brakes with a little effort. For the remaining adjustments, be sure your wheels are true, or laterally aligned. To check, spin the wheel. If it has a noticeable side-to-side wobble or up-and-down “hop,” it’s not true. Bike shops are well-equipped to true wheels.
Brake Pads
If your bike has caliper brakes, center-pull brakes, or linear-pull (“V”) brakes, you will need to check the brake pads that push against the wheel rim for wear. If there is less than a quarter inch of rubber outside the brake pad base, or if the pads are glazed and hard, replace both brake pads on that assembly. To make sure you get the correct replacements, take the old pads to a bike shop as examples. Worn brake pads can be shaped with a file or sandpaper to remove any “shelves” formed by the pads riding below the wheel rim. The file also will remove any glazing from the surfaces of pads.
Coaster Brakes
The coaster brakes are housed in the hub of the rear wheel and are applied by pedaling backward. While the hub protects them from the weather, coaster brakes have several disadvantages. They take longer to apply than hand brakes, they affect only the rear wheel, and you must have the pedals in position for pedaling backward to apply them.
Please note: Coaster brakes should be adjusted and serviced only by a bicycle repair specialist, but you can adjust hand brakes with a little effort.
Hand Brakes
Hand-operated brakes provide more stopping power and control than coaster brakes. However, hand-operated brakes may need more frequent adjustment. Cables need to be checked and occasionally replaced to prevent snapping; brake pads wear down and need to be replaced.
When hand-brake levers are fully squeezed, there should be at least an inch of clearance between the levers and handlebars. If not, the brakes need to be tightened.
Hand-Brake Levers
Levers mounted on the handlebars control rim brakes and disc brakes. Stopping force is created by friction. In a rim brake, that friction is from the brake pads pushing on the sides, or “rims,” of the wheel; for a disc brake, the friction comes from pistons in a brake caliper pushing brake pads against a disc rotor attached to the wheel, like in a car. The brakes work through either a flexible cable pulling the brake pads against the wheel rim or disc rotor, or, for hydraulic disc brakes, a fluid that pushes pistons into the brake pads and against the rotor.
Disc Brake
In a disc brake, the friction comes from pistons in a brake caliper pushing brake pads against a disc rotor attached to the wheel, like in a car.
Rim Brake
In a rim brake, that friction is from the brake pads pushing on the sides, or “rims,” of the wheel.
Helpful Tip:
Check out this article on how to properly adjust a caliper-rim brake, linear-pull brake (known as a V-brake), or disc brake.
Adjusting Caliper-Rim Brakes
If your bike has caliper brakes, center-pull brakes, or linear-pull (“V”) brakes, you will need to check the brake pads that push against the wheel rim for wear. If there is less than a quarter inch of rubber outside the brake pad base, or if the pads are glazed and hard, replace both brake pads on that assembly. To make sure you get the correct replacements, take the old pads to a bike shop as examples. Worn brake pads can be shaped with a file or sandpaper to remove any “shelves” formed by the pads riding below the wheel rim. The file also will remove any glazing from the surfaces of pads.
Adjusting Linear-Pull Brakes, or V-Brakes
Adjust brake pads by loosening the mounting nut and aligning the pad with the rim of the wheel. Pull the brake arm toward the rim to hold the pad in position when retightening the mounting nut. Add a little toe-in so that the front of the pad contacts the rim first.
Adjusting Disc-Brake Pads
If your bike has disc brakes, replace the pads when they wear down to three millimeters thick or less. Inspect your disc-brake pads at least monthly and check the disc rotor to make sure it is not warped or bent. Hydraulic brakes require much less maintenance than rim brakes and are self-centering as the brake pads wear down. For mechanical brakes, you may need to adjust the tension of the brake cable as well as adjust the centering of the brake pads in the caliper. Check the manufacturer’s instructions for your brakes to see how to do these tasks. If your disc-brake pads have become contaminated (slippery or unable to “grab” the disc), clean the pads with isopropyl alcohol, which can also be used to clean the rotors. You can also lightly sand the surface of the pads. Do not use any solvent other than isopropyl alcohol to clean pads.
Adjusting Brake Cables
Step 1
To adjust your brake cable, loosen the main anchor bolt. Squeeze the brake lever; unscrew the barrel adjuster. This frees the cable for loosening or tightening to decrease or increase cable tension.
Step 2
After pulling the main brake cable taut through the anchor bolt, screw in the barrel adjuster and tighten the bolt. If you need to use pliers, do so carefully to avoid causing the cable to fray. Check the tension and readjust if necessary.
Step 3
After the brakes are centered, check the whole brake system by squeezing the lever several times to see that the parts work promptly, nothing slips, and everything returns to a natural position when the levers are released.
Bike Brake Adjustment: Watch This Video to Learn How
Gearing
Gearing lets you adjust the bike’s efficiency—the effort required to move the gears—based on speed and terrain. When you shift to a low gear as you are climbing a hill, the wheels won’t move as far on each pedal stroke, but you also won’t have to work as hard. When you shift to a high gear when you are moving quickly, each pedal stroke will move the wheel a greater distance. There are three main types of gearing: fixed gearing, multispeed internal gearing, and derailleur gearing.
Shifting Techniques
Fixed Gearing
A fixed-gear bike has only one gear, which may be high, low, or in between. In this gearing system, the pedals always move with the wheel. Fixed gearing is mostly found on utility bikes and track bikes, although some elite riders actually prefer “fixies,” as they are called, to multispeed bikes.
Multispeed Internal Gearing
Bikes with multispeed internal gearing usually have three or five speeds. The lowest-numbered gear is for pedaling uphill or against strong winds. The highest-numbered gear is for traveling at a higher speed downhill or with a tailwind. This system’s benefits include weather resistance and easier cleaning and maintenance.
Derailleur Gearing
A derailleur moves the chain (literally derails it) from a sprocket or chainring of one size to a sprocket or chainring of another size, changing the bike’s gearing. The chain passes through a guide, or cage, that moves it to the various sprockets or chainrings as needed. This cage is connected by a flexible cable to a control mechanism near the rider’s hands.
Did You Know:
Some bikes have a derailleur on just the rear wheel, while other bikes have front and rear derailleurs. Determine the number of possible gear combinations by multiplying the number of sprockets (cogs) on the rear cluster by the number of chainrings at the pedals. For example, a bike with seven rear cogs and three chainrings (front sprockets) has 21 gear combinations.
Now that you have learned how to adjust brakes and gear shifting on your bike,
let’s learn about all of the points on a bike needing regular lubrication.
