Most people tend to use the terms wheel, rims and hubcap interchangeably. However, they are not the same thing. As much as they all come from one area in a vehicle, wheels, rims and hubcaps are completely different things. In this guide, we will explore what each part means, its different components as well as the key differences between these terms.
Every car on the road, regardless of its type, model, design or manufacturer relies on one simple machine. And this is the wheel. The wheel is the circular component of the car, which provides a point of contact between the vehicle and the ground. Without wheels, it would be almost impossible to drive a vehicle from one point to the other.
Parts of a Wheel
As mentioned above, wheels are the circular structures in a vehicle that produce rotary motion. And while they may differ in size, structure or style from one vehicle to the other, they all play the same role. Also, wheels usually come with almost identical parts. Let’s take a closer look at the different parts of a wheel.
The rubber is the outermost, rubber part of the wheel. It’s usually the first thing that you will notice when you look at a wheel. Tires are usually black, and they make contact with the ground.
Tires are made of rubber, which can be natural or synthetic, depending on the manufacturer. The majority come inflated with compressed air. And this explains why they are called pneumatic tires.
Besides covering the wheel, tires also provide a form of cushioning for the vehicle. Also, they act as one of the vehicle’s shock absorbers. If are driving on rough terrain, tires will absorb the impact generated from such bumpy terrains, resulting in a comfortable ride.
Tires are available in a wide range of sizes and specifics. Usually, the tire’s specs are usually imprinted on its sidewalls. Besides the tire’s sizes, you will also find other specifications on the tire’s sidewall like the width, temperature grades, load index, ply construction, wheel diameter and load limit, among others.
There’s plenty of confusion surrounding the wheel and the rim. And this explains why some people tend to refer to the wheel as the rim or the rim as the wheel. However, these two parts of a vehicle are not the same thing.
The wheel is the entire circular part, which includes the rim. On the other hand, the rim is the metallic component of the wheel. The main role of a rim is to support the tire in place.
The wheel hub or the hub as most people like to call it is the central-most part of the wheel. It comes with studs, onto which the entire wheel is connected. It also features a central hole, which provides a point for attaching the wheel onto the axle.
A vehicle’s brake discs are also located within the wheel hub. So, when a driver hits the brake pedal, the brake discs will press against the wheel hub, thus bringing the vehicle to a stop.
Most wheel hubs come with a removable cap, found on the wheel’s exterior. This removable cab helps to cover the central bore. In most wheels, the rim and the hub are connected via a wheel disc. This wheel disc can be permanently attached or detachable, depending on the wheel’s design.
You may also come across various types of wheels, which use spokes to connect the hub and the rim. Most wheels these days feature stylish spokes, designed to enhance a vehicle’s aesthetics.
The main function of the hub is to enable the wheel to turn smoothly. Also, it holds the vehicle’s wheel speed sensor. Hence, it’s extremely vital when it comes to a vehicle’s steering and braking.
As mentioned above, the rim is the cylindrical metallic part of the wheel, onto which the vehicle’s tire attaches.
Parts of a Rim
Similar to the wheel, the rim is also made up of different parts and components. All these components work together to ensure the wheel can deliver its functions effectively and efficiently. Here are some of the parts that make up the rim.
As their name suggests, the lug holes provide an area where the lug bolts are nuts will be fastened into place, to ensure the wheel remains mounted securely onto the rest of the vehicle.
Different vehicle models come with different numbers and variations of lug holes. But in most vehicles, you will find a five-bolt pattern, meaning it has five lug holes, which will provide attachment points for five bolts or lugs. Some aftermarket rims come with up to eight lug holes.
The valve stem forms an important part of the vehicle’s air pressure monitoring system. It’s more of a small metal tube, which is inserted into the valve stem hole.
The valve stem will then provide a provision for the tire’s inflating or deflating. A damaged or defective valve stem is one of the leading causes of leaks in tires. Considering that the valve stem is integrated into the vehicle’s tire pressure monitoring system, it’s easy for the driver to determine the tire’s pressure at all times.
The rim lip forms the rim’s visible part. It traverses the wheel’s entire width. The rim has an outer lip and an inner lip. The visible part is usually the rim’s outer lip while the inner lip remains hidden inside the wheel.
Considering the position of the lip, it’s the part of the wheel that will get damaged the most. For instance, whenever you are driving and the wheel rubs against a curb, the wheel will take that abuse. And as this continues, the lip will considerably deteriorate, making it extremely hard for tire mounting and other maintenance procedures. And at this point, replacing the rim is no longer an option.
The flange begins where the inner lip ends. It’s usually the part that helps the tire to remain securely mounted onto the wheel. During tire mounting, the tire has to be carefully placed on the flange, to ensure it remains secured in position at all times.
Similar to the lip, a rim’s flange can also suffer damage. Once it's damaged, the entire wheel will not be holding air properly, once it has been inflated. Also, a damaged flange can lead to safety issues when it comes to mounting or dismounting a tire. Hence, it needs to be replaced once the damage becomes visible.
Tires come with a part known as a bead. A bead is usually a thick, sturdy circumferential loop on the tire’s edge. This bead then rests on the rim, forming an airtight mechanism. This airtight mechanism helps to prevent air from escaping from the tire.
The part of the rim where the bead encounters the rim is known as the bead rest. The bead rest features two grooves, forming a shallow valley onto which the tire’s bead rests. The bead rest is usually positioned in the flange section.
Also known as the tire well, the drop center helps in tire mounting. It traverses the entire circumference of the rim. During tire mounting, the drop allows the tire installer to slide it over the wheel’s barrel while preventing damage to the tire’s bead or other areas.
A hubcap is a decorative element that you may find on some wheels. This disk usually covers the central section of the wheel, which is known as the wheel hub. Once fitted, the hub cap is designed to securely cover both the wheel hub as well as the lugs, thus preventing the build of dirt, dust, moisture and debris. Hubcaps also play a secondary role in preventing nuts and lugs from falling out, in case they become loose on the way.
Hub caps are usually made of plastic or metal. They may feature various stylistic elements, designed to enhance a vehicle’s aesthetics. Hubcaps are usually found in older vehicle models or trucks. Most of the modern vehicles come with sealed wheel hub assembly, meaning hubcaps may not be required.
Rims vs. Wheels
In a nutshell, the rim is the outer, metallic part of the wheel. It plays an important role in holding the tire in position. The wheel, on the other hand, is the entire system. Rims are part of the wheel. Besides the rim, the wheel also features the tire, the hub, and various other vital components.
So, as much as some people may be using these two words interchangeably, they don’t refer to the same thing. Simply put, the wheel is the entire system, made up of different components and parts. The rim, on the other hand, is one of the parts of a wheel.
Rims vs. Hubcaps
Rims and hubcaps are completely two different things. In terms of construction, rims are usually made of solid, sturdy metal. Since they form a core part in supporting the weight of a vehicle, rims have to be sturdy. In most cases, rims are usually made of solid steel.
Hubcaps, on the other hand, only play a role in protecting the wheel hub against dirt or moisture. While you can’t drive a vehicle without a rim, you can easily do so without hubcaps, since their role is mainly secondary.
Simply stated, hubcaps are additional attachments or components on the wheels. They are not a core component of the wheel, unlike rims. Hence, they don’t play a core role in the optimal functioning of your vehicle’s wheels.
Wheel Hubcaps Vs. Wheel Covers
Some people use hubcaps and wheel covers interchangeably. However, while they serve almost the same purpose, these two parts are different. As mentioned above, hubcaps are mainly designed to protect the wheel hub against dirt and moisture. It usually covers the wheel hub.
Wheel covers, on the other hand, are designed to cover the entire diameter of the wheel. But just like the hubcaps, wheel covers also protect the nuts against the elements. Besides protecting the nuts and lugs from moisture and dirt, both can also be used to enhance a vehicle’s aesthetics.
Wheel covers attach directly onto the rim. Hence, you can attach or remove them without any special tools, which is usually not the case with hubcaps. It’s also worth mentioning that wheel covers are universal for the wheel size.
For instance, a size 17 wheel cover from a certain vehicle will likely mount comfortably onto another vehicle’s wheel, as long as the wheel is a size 17. With hubcaps, it’s not easy to accomplish that.
Both the hubcap and the wheel cover attach onto the wheel using the same approach. Hence, there isn’t much difference in this area.
Wrapping It Up
As you can see, wheels, rims and hubcaps don’t refer to the same thing. They come with considerable differences. And while they are all part of a vehicle’s wheel system, it would be wrong to use them interchangeably.
About The Author
I've spent many years selling cars, working with auto detailers, mechanics, dealership service teams, quoting and researching car insurance, modding my own cars, and much more.Read More About Charles Redding