Every car, from Ferrari to Ford Pinto, relies on the simplest machine: the wheel. There is no bypassing (pun intended) right next to the fire, the wheel could be the greatest discovery man has ever made. Without wheels and tires, cars and trucks would be little more than expensive lawn ornaments.
From car to car, wheels and tires perform the same function. The only difference is in size, style, and structure. In order to expand your knowledge base about cars, trucks, and how they work, the basic parts of a car wheel and tire are explained below. When you know more about your vehicle, you can look after it better and keep it running for many years.
Parts of a Car Wheel
The wheel includes the hub, spokes, and rim. The point of contact for the axle seat, the lug bolts, and the lateral surface of the rotor.
The tire is, of course the outstanding component of every car wheel. After all, it’s the outermost part and the first thing you notice when you look at a car wheel. The tire is the ring-shaped outer shell. Most car tires are inflated using compressed air, which is known as pneumatic. They are made of rubber (synthetic or natural), carbon black and some chemical compounds.
Tyres cover and prevent the rim from rubbing or touching the ground. It cushions and also acts as a shock absorber when you’re driving on bumpy terrain. 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 a tread pattern. This pattern has two important functions to increase the friction between the ground surface and the tire and to draw water and dirt 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 tyre’s sidewall include the following:
- Width of the tyre
- The ratio of height to width of the tyre
- The diameter of the wheel
- Treadwear, traction, and temperature grades
- Tyre ply composition and materials used
- Load index and speed symbol
- Inflation and load limit
Confusion usually arises between the rim and the wheel. People sometimes refer to the wheel as a rim and vice versa. Let’s distinguish between the two the rim is only part of the wheel, while the wheel is made up of the rim, tire and other components.
The rim is the outer edge of the skeleton that holds the tire in place. It is cylindrical and allows the annular housing to be held and sealed on the wheel. With tubeless tires, proper assembly between the tire and the rim is crucial to seal the air inside. Old generation cars had tubes between the rim and the tire.
The rims are made of sturdy metal such as steel to withstand the force and load of the vehicle. The width and diameter of the rim determine the size of the car tire. You can get custom rims as aftermarket auto parts. These bespoke rims are colored and styled to your liking but come at an additional cost.
The barrel of the rim creates a surface for the tire to be mounted on. The inside diameter of the cylinder is the center of fall, which determines the type of wheel mounted. For front-mounted wheels, the drop center is near the front of the wheel. On the other hand, rear-mounted wheels have fall centers near the back of the wheel.
The barrel edges are shaped to form flanges that ensure the tire does not slip while driving. Inside them are flat sections referred to as beads. These flat sections form a surface on which the edge of the tire rests.
The hub is the most central part and has studs to which the wheel is attached. It has a central hole that is the opening for mounting the wheel on the axle. The brake discs lie against the wheel hub to ensure that the car brakes when the driver steps on the brake pedal.
A removable center cap on the outside of the wheel covers the central hole. The hub and the rim are usually connected by a wheel disc which is either detachable or permanently attached to the rim. Other automobile wheels use spokes to connect the rim and hub. The spokes also give the wheel its structural integrity. Most of the wheels these days have stylized spokes for added appeal.
When purchasing an aftermarket car wheel, make sure that the central hole is the same size as the OEM or OE wheel. Using wheels with a larger central bore will cost you more as you will need hub centered rings to fill in the gap.
In the case of spoked car wheels, the center disk is located directly outside the center cap. The depth of this disc relative to the center line determines the wheel offset.
Lug holes are typically machined to create bolt circles on the center disc. Lug holes are the holes where the wheel nuts are attached. The Lug holes create bolt circles with a diameter called the bolt circle diameter (BCD). This diameter and the number of holes define the bolt pattern.
Car tires are inflated or deflated through their valve system. Car wheels have a valve mechanism that is integrated into the tire pressure monitoring system so that the driver knows the pressure status at all times.