Over the years, cars have taken various body types, designs, and shapes. Some auto parts are now obsolete and eliminated or replaced with new versions. Among the car parts that have remained in use all along are the wheels.
These circular structures produce rotary motion and are responsible for moving the car from one point to another. The wheels are, therefore, essential parts of any automobile. Since its invention in 3500 BC, these circular blocks have taken various designs, structures, and styles. Nonetheless, their function has remained the same.
The car wheel parts perform different roles to ensure that it functions as expected. Some of car wheel parts have been subjects of misunderstanding and confusion. Below we breakdown these parts and understand their structure, functions, and adaptations.
Parts of a Car Wheel
The tire is, of course, the prominent component of any car wheel. After all, it’s the outermost part and the first thing that you notice when you look at a car wheel. The tire is the ring-shaped outer covering. Most of the car tires are inflated with compressed air, thus called pneumatic. They are made from rubber (synthetic or natural), carbon black, and some chemical compounds.
Tyres cover and prevent the wheel rim from rubbing or touching the ground. It also cushions and acts as a shock absorber when you drive on bumpy terrains. The main parts of the tire are the treads and its body.
The tread or track is the outermost rubberized part of a tire. It is in direct contact with the ground and wears out over time. The tread has grooves and notches, called the tread pattern. This pattern has two important roles – to increase friction between the ground surface and the tire and to direct water and debris away from the wheel.
The body, on the other hand, acts as a housing for a specified quantity of compressed air. Tires come in various sizes to fit different cars. You can find the size and other specs of your car’s tire stamped on its sidewall. You may also find it etched or printed on the glovebox door, on your door jamb (driver’s side), or within the fuel tank hatch.
The specifications found on the tire’s sidewall include the following:
- Width of the tire
- The ratio of height to width of the tire
- The diameter of the wheel
- Treadwear, traction, and temperature grades
- Tire ply composition and materials used
- Load index and speed symbol
- Inflation and load limit
2. The Rim
Confusion usually arises between the rim and the wheel. People sometimes refer to the wheel as the rim and vice versa. Let’s differentiate between the two – the rim is only a part of the wheel, while the wheel comprises the rim, tire, and other components.
Read more: Car Wheel Anatomy | Car Construction
The rim is the skeletal outer edge that holds the tire. It is cylindrical, allowing it to hold and seal the ring-shaped casing to the wheel. For tubeless tires, proper fitting between the tire and the rim is crucial to seal the air inside. Old generation cars had inner tubes housed between the rim and the tire.
Rims are made from sturdy metal such as steel to withstand the force and load of the car. The width and diameter of the rim determine the size of the car tire. You can get customized rims as aftermarket car spare parts. These customized rims are colored and styled to your liking, but they come with additional cost.
The barrel of the rim creates a surface for mounting the tire. The inner diameter of the barrel is the drop center, which determines the mount wheel type. For front-mounted wheels, the drop center is near the wheel’s front face. On the other hand, rear-mount wheels have drop centers near the wheel’s back face.
The barrel edges are shaped to form flanges, which ensure that the tire doesn’t slip off when the car is in motion. Inside them are flat sections referred to as beads. These flat sections provide a surface upon which the edge of the tire rests.
3. The Hub
The hub is the centermost part and has studs onto which the wheel attaches. It has a central bore which is the port for fitting the wheel on the axle. The brake rotors rest against the wheel hub to ensure the car brakes when the driver presses on the brake pedal.
A removable center cap on the outer side of the wheel covers the central bore. The hub and rim are usually linked by a wheel disc which is either detachable or permanently conjoined with the rim. In other car wheels, spokes are used to connect the rim and the hub. The spokes additionally give the wheel its structural integrity. Today, most wheels have stylized spokes for added appeal.
When buying an aftermarket car wheel, make sure that the central bore is equal to the size of the OEM or OE wheel. Using wheels with a larger central bore will cost you more since you will need hub-centric rings to fill the gap.
For spoked car wheels, just outside the center cap is the center disc. The depth of this disc relative to the centerline determines the wheel offset.
Lug holes are usually machined to create bolt circles on the center disc. Lug holes are the holes into which the lug nuts are fastened. The lug holes create bolt circles with a diameter called the bolt circle diameter (BCD). It is this diameter, as well as the number of holes that define the bolt pattern.
4. Valve System
Car tires get inflated or deflated through their valve system. Car wheels have a valve mechanism integrated with the tire pressure monitoring system to help the driver know the pressure condition at all times.
Please see more list about Parts of a car wheel