Rims and wheels are one of those things that are used interchangeably so many times that it confuses many and annoys those who actually know the difference. I bet you have been corrected before when you used rims while talking about wheels and it left you wondering if they are different or it’s just a marketing or a technical language. To answer your question, yes, they are different and in this article, we will explore the difference so that you too can get annoyed at the next person who mixes up these two.
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Simply put, the rim is one of several parts that make up the wheel. That is the main difference, the fact that the rim is not the whole wheel but only a part of the wheel, while the key parts of the wheel are the rim and the disc. Many people use the term wheel as a rim meaning the entire metal part to which the tire is mounted but the rim is the outside edge of the wheel where the tire sits. It does not include the spokes or central wheel disc, which also make up the wheel. So technically the rim is just the outer edge, the outside lip while the wheel is the entire assembly including the spokes and hub, wheels are what you put tires on.
Another difference between rims and wheels is how they operate. A wheel rotates to allow a vehicle or other heavy equipment to move and hence a car wheel includes a rim, and a tire. To be able to rotate, wheels are connected in parallel pairs, through their center, by an axle. The rotating motion moves the vehicle forward or backward, depending on which direction the wheel rotates.
What is a Rim?
The rim is a cylindrical outer edge of a wheel holding the tire on the wheel. It is usually U-shaped and it is deeper in the center than around the edges since this provides support to the bead of the tire. The rim is normally made from the same metal or alloy as the rest of the wheel, although for extra protection a layer of Teflon might be added.
Rim’s main function is to support and seal the tire on the wheel, the rim is the part of the wheel that the tire wraps around. The rim ensures proper fitting between tire and rim and retains the air inside the tubeless tire. This way the rim supports the tire and gives it form while allowing it to fill with air. Rims have different diameters and widths that hold different sizes of tires.
You might have heard the term ‘rims’ used to describe the after-market decorative wheels which are usually chrome, alloy, or another shiny and durable material. As important as a wheel is to a vehicle it can become damaged. Rims are one of the areas of the wheel most likely to meet the curb when parking so it plays an important part in maintaining the safety of your car, and its condition directly affects the handling of your vehicle. So if your wheel rim has become damaged, you must get it fixed quickly, to prevent blowouts and poor handling.
What is a Wheel?
The term “wheel” is often used to describe the entire assembly, including the tire, but this isn’t always true, the wheel is just the entire metal section that holds the tire. Apart from supporting the car’s movement, the wheels also reduce tire friction, support your vehicle, and provide stability.
The wheel is made of the tire, the rim, and the hub. Each of these components has several other parts that complete the functionality of the wheel. The tire is held onto the wheel with tire beads and supports the vehicle while providing traction using the treads.
Here are parts that make up the wheel and their function, skipping the rim since it is already explained above;
The Hub
The hub is the central part of the wheel and is attached to the rim. It has a central hole that is the opening for mounting the wheel on the axle. This part holds several components including the brake pads, the rotors, and the calipers that are not parts of the wheel itself. The brake pads lie against the wheel hub to ensure that the car brakes when the driver steps on the brake pedal.
Barrel
The barrel gives the shape and surface for mounting the tire. The barrel surface closes to help maintain and retain the air pressure inside the tire.
Drop Centre
The drop center is the portion of the barrel that is bent towards the inside of the wheel. This is the central and narrow part of the barrel. It gives support to the tire. To mount the tire properly on the rim, one side of the tire gets inserted into the drop center. This will allow the tire to move enough so that the other side can adequately hold on to the edge of the rim. The drop center is always near one of the edges of the wheel.
Outer Lip
This is the outer edge of the wheel. This is the part that usually gets damaged or bent when you drive the vehicle hard over a pothole or a curb and due to the high impact, it gets bent. It happens due to not getting that much support from the spokes.
Flanges
Flanges are the edges of the wheel designed to prevent the tire from slipping while a car is running on the road. These are located at both ends of the wheel. It also prevents slippage of the tire during harsh conditions like heavy rides, uneven roads surfaces.
Spokes
Spokes are the structural member that connects the rim and hub. They are the pieces that are between the edge of the rim and the plate in the center of the wheel. The spokes are for the structural integrity of the wheel. In some vehicles, it is inbuilt with a rim, and in some vehicles it is separate. The spokes also support the outer edge and prevent damage from minor impacts.
Lug Holes
Lugholes are the holes around the center bore. They are the empty spaces covered by the center cap. They are for passing bolt to attach wheel with the axle. The lug nuts hold the wheel together and determine the bolt pattern.
Bolt Circle
It is an area created by the lug bolt. The Bolt Circle Diameter is the length between the area and is referred to as the BCD. The number of lug bolt holes in the wheel plus the BCD makes the bolt pattern (so 5 lug bolt holes and a 4 inch BCD would be a 5×4” bolt pattern). The bolt pattern can vary between the wheel and car manufacturers and make it difficult to cross fit wheels that are designed for different car manufacturers.
Valve Stem
A valve stem hole is a place on the wheel that we use to fill the tires with air or to check the current air pressure of the tire. The valve mechanism in the car is used to evaluate and monitor the air pressure inside the tire. It helps to avoid any damage or accident due to less air pressure inside the tire. There are a few different types of valve stems on the wheel, some are rubber stems which are commonly used and metal stems that are designed for aesthetics.
Centre Bore
The center bore is an empty area on the backside of the wheel. Its function is to support the weight of the vehicle and that’s why it is at the center and on the wheel’s backside. This makes it one of the most important parts of the entire tire and its measurements must be correct if you are replacing a wheel.