Bicycle Parts Explained: Wheels, Chain, Pedals
Bicycle Wheels (Rims)
Bicycle rims are typically made of aluminum alloys and are quite flexible, resistant, and light. They have wheels that are stronger and heavier than road wheels, and feature a series of holes on the left and right where the heads of the spokes connect. These drill holes are protected to avoid puncturing the inner tube. Rims also often have a hand protector and a larger hole where the valve of the inner tube exits.
Inner Tubes and Valves
The main difference between valve types is how easily they support air pressure. Presta valves (sometimes called Sclaverand) are narrower and often require an adapter for standard pumps, but hold high pressure well. Schrader valves are the same as those on cars and are generally more practical and easier to use with standard pumps, including those at gas stations.
Your inner tube should be suitable for the wheel size and rim type. Latex tubes are sometimes used for performance but are less common. The most commonly used are rubber tubes, which adapt to different sizes and are more suitable for dealing with stones, potholes, and other road hazards.
Spokes and Nipples
Spokes emerge from the hub and connect to the rim. They should be made of stainless steel and typically have a diameter of around 2mm, though this can vary. The small nut that fastens the spoke to the rim is called a nipple.
Spoke Lacing Patterns
Spokes can be mounted in various patterns, such as 8, 6, or 4 cross. Patterns like 8 or 6 cross generally offer more elasticity in the wheel build.
Specialized Wheel Builds
Some wheels feature particular spoke geometries or materials. For example, some designs might have spokes emerging in pairs or groups from the hub, or use materials like Kevlar fiber. Kevlar is very resistant to impact and can allow for high speeds on flat surfaces, though it weighs a little more and is much more expensive than traditional steel spokes.
Bicycle Hubs
Hubs are the central components of the wheel where the axle is located and where the spokes are inserted. They contain bearings that allow the wheel to spin freely. There are two main types of bearings:
- Sealed Bearings: These have the bearing unit isolated inside, preventing the entry of dirt, water, etc. They are more expensive but generally offer better performance and durability.
- Non-Sealed Bearings (Cup and Cone): These can be mounted and dismounted for maintenance. They are cheaper but are more susceptible to water entry, which can lead to oxidation and reduced performance.
Wheel Truing and Centering
Keeping your wheels true (straight and round) is essential. The front wheel should always be centered symmetrically. The rear wheel’s spoke tension and centering might differ slightly depending on the cassette or freehub size.
To true a wheel, you need a spoke wrench of the correct size for your spoke nipples. Lateral deviations (side-to-side wobbles) or vertical deviations (up/down hops) can be difficult to see but must be corrected.
Correcting Deviations
- If the rim deviates to the right, center it by tightening spokes on the left side or loosening spokes on the right side at the point of deviation.
- If the rim deviates to the left, center it by tightening spokes on the right side or loosening spokes on the left side.
- Spokes are typically tightened by turning the nipple clockwise when viewed from the spoke head side (or counter-clockwise when viewed from the rim side).
- Tighten nipples only a quarter or half turn at a time and re-check the wheel. Never do several full turns at once.
- To correct vertical deviations (hops), tighten spokes on both sides at the point furthest from the rim center (the peak of the hop).
The Bicycle Chain
The chain is a system of links that transmits the force from pedaling to the rear wheel. It is comprised of different segments called links, each composed of rollers and pins. Links can be internal or external.
Chains suffer wear over time due to factors like shock, mud, and rocks. This wear negatively affects their performance and can lead to breakage, especially under strong tension or from external agents.
Chain Maintenance Tips
- Always carry a chain tool (or quick link) on rides.
- Clean the chain after rides, especially in dirty conditions.
- Lubricate the chain often.
- Change the chain when it is stretched (worn).
- If you change the cassette or sprockets, you should also change the chain.
Bicycle Pedals
Pedals are the components you push with your feet to propel the bicycle. Cheaper models may be made of plastic, while more durable ones are made of steel or aluminum alloy.
Many pedals feature toe clips or other foot retention systems. Common types of foot retention include:
- Toe clips with straps
- Toe clips without straps
- Power grips (straps that wrap over the shoe)
- Automatic fixation pedals (clipless pedals that require special shoes)