Rim (wheel)
The rim of a wheel
A wheel is a device that allows heavy objects to be moved easily through rotating on an axle through its center, facilitating movement or transportation while supporting a load, or performing labor in machines. Common examples found in transport applications. A wheel, together with an axle,...

 is the outer circular design of the metal on which the inside edge of the tire
A tire or tyre is a ring-shaped covering that fits around a wheel rim to protect it and enable better vehicle performance by providing a flexible cushion that absorbs shock while keeping the wheel in close contact with the ground...

 is mounted on vehicles such as automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...

s. For example, on a bicycle wheel
Bicycle wheel
A bicycle wheel is a wheel, most commonly a wire wheel, designed for bicycle. A pair is often called a wheelset, especially in the context of ready built "off the shelf" performance-oriented wheels....

 the rim is a large hoop attached to the outer ends of the spokes of the wheel that holds the tire and tube.

In the 1st millennium BC an iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 rim was introduced around the wooden wheels of chariot
The chariot is a type of horse carriage used in both peace and war as the chief vehicle of many ancient peoples. Ox carts, proto-chariots, were built by the Proto-Indo-Europeans and also built in Mesopotamia as early as 3000 BC. The original horse chariot was a fast, light, open, two wheeled...



  • Diameter (effective): distance between the bead seats (for the tire), as measured in the plane of the rim and through the axis of the hub which is or will be attached, or which is integral with the rim.

  • Width (effective): separation distance between opposed rim flanges. The flange-to-flange width of a rim should be a minimum of three-quarters of the tire section width. And the maximum rim width should be equal to the width of the tire thread.

  • Type: Depends on the type of vehicle and tire. There are various rim profiles, as well as the number of rim components.
Modern passenger vehicles and tubeless tires typically use one-piece rims with a “safety” rim profile. The safety feature helps keep the tire bead held to the rim under adverse conditions by having a pair of safety humps extending inwardly of the rim toward the other tire bead seat from an outer contoured surface of the rim.
Heavy vehicles and some trucks may have a removable multi-piece rim assembly consisting of a base that mounts to the wheel and axle. They then have either a side ring or a side and lock ring combination. These parts are removable from one side for tire mounting, while the opposite side attached to the base has a fixed flange.

  • Vehicle performance: Because the rim is where the tire resides on the wheel and the rim supports the tire shape, the dimensions of the rims are a factor in the handling characteristics of an automobile. For example:
Overly wide rims in relation to the tire width for a particular car may result in more vibration and less comfortable ride because the sidewalls of the tire have insufficient curvature to flex properly over rough driving surfaces. Oversized rims will cause the tire to rub when turning.
Overly narrow rims in relation to the tire width may cause poor handling as the tire may distort sideways under fast cornering. On motorcycle
A motorcycle is a single-track, two-wheeled motor vehicle. Motorcycles vary considerably depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions.Motorcycles are one of the most...

s, a narrow rim will alter the tire profile, concentrating tire wear in a very small area during cornering, with a smaller contact patch during braking.
On bicycles, the optimum tire width is approximately twice the rim's internal width (e.g. a 35mm tire on a rim with an ETRTO 17mm internal width) or one-and-a-half times the rim's external width. Considerable variation outside this range is safe, but very wide tires on a narrow rim can overstress the rim and damage the tire sidewalls, whereas very narrow tires on a wide rim give a hard ride and can result in a high-pressure tire blowing off.


A standard automotive steel wheel rim is made from a rectangular sheet metal. The metal plate is bent to produce a cylindrical sleeve with the two free edges of the sleeve welded together. At least one cylindrical flow spinning operation is carried out to obtain a given thickness profile of the sleeve — in particular comprising in the zone intended to constitute the outer seat an angle of inclination relative to the axial direction. The sleeve is then shaped to obtain the rims on each side with a radially inner cylindrical wall in the zone of the outer seat and with a radially outer frusto-conical wall inclined at an angle corresponding to the standard inclination of the rim seats. The rim is then calibrated.

To support the cylindrical rim structure, a disc is made by stamping a metal plate. It has to have appropriate holes for the center hub and lugnuts. The radial outer surface of the wheel disk has a cylindrical geometry to fit inside the rim. The rim and wheel disk are assembled by fitting together under the outer seat of the rim and the assembly welded together.

One-piece rim and wheel assemblies (see image) may be obtained by casting
In metalworking, casting involves pouring liquid metal into a mold, which contains a hollow cavity of the desired shape, and then allowing it to cool and solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process...

 or forging
Forging is a manufacturing process involving the shaping of metal using localized compressive forces. Forging is often classified according to the temperature at which it is performed: '"cold," "warm," or "hot" forging. Forged parts can range in weight from less than a kilogram to 580 metric tons...


Life Span of a Rim

As the point of contact between a vehicle and the road (or whatever surface is being driven on), a wheel rim is subject to a number of conditions that can reduce its effectiveness or even disable it entirely. Any damage---such as rust, cracks, dents, etc---could result in excessive vibration, loss of air pressure, instability, and even complete structural failure. Because of this, damage to wheel rims is very serious, as it could result in a traffic collision. Though repairs can be made to a wheel's rim, visible damage could be indicative of greater damage that cannot be easily noticed, so a repaired wheel rim will never be structurally as sound as a new one.

A general life-span for wheels is difficult to determine, as it depends heavily on the composition of the wheel and the use to which the vehicle is being put. Wheels made with low-profile rims and lighter alloys---such as aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

 alloy wheels---are more likely to be damaged by regular road use. Additionally, wheel rims will take more damage from such severe uses as rallying
Rallying, also known as rally racing, is a form of auto racing that takes place on public or private roads with modified production or specially built road-legal cars...

 (where racers compete on public streets which may have more surface inconsistencies and damage than dedicated race courses), high-speed off-roading
Off-roading is a term for driving a vehicle on unsurfaced roads or tracks, made of materials such as sand, gravel, riverbeds, mud, snow, rocks, and other natural terrain.-Off-road vehicle:...

, and other activities that result in high-stress impacts to the wheels and tires. Using a vehicle without sufficient air pressure in the tires is another likely cause of damage to wheel rims. What can be generally said about wheel life-span is that it is almost always longer than the life-span of a tire, and many vehicles go their entire lives without repairing or replacing any wheels.


The terms "wheel" and "rim" are often used synonymously, as in decorative wheels being called rims. Some authors are careful to use "rim" for only the outer portion of a wheel, where the tire mounts, just as the rim of a coffee cup
Coffee cup
A coffee cup may refer to a type of container from which coffee is consumed. Coffee cups are typically made of glazed ceramic, and have a single handle, allowing for portability while still hot...

 or a meteor crater
Rim (craters)
The rim of a crater is the part that extends above the height of the local surface, usually in a circular or elliptical pattern. In a more specific sense, the rim may refer to the circular or elliptical edge that represents the uppermost tip of this raised portion...

 does not refer to the entire object. Others use "rim" to mean the entire metal part to which the tire mounts, because the rim and the wheel are often cast or stamped from a single piece of metal instead of being distinct as with wire wheels
Wire wheels
The rims of wire wheels are connected to their hubs by wire spokes. Although these wires are generally stiffer than a typical wire rope, they function mechanically the same as tensioned flexible wires, keeping the rim true while supporting applied loads.Wire wheels are used on most bicycles and...

. At the same time, "wheel" may refer to the entire rotating assembly, including the tire.

Railroad usage

In railroad
Rail transport
Rail transport is a means of conveyance of passengers and goods by way of wheeled vehicles running on rail tracks. In contrast to road transport, where vehicles merely run on a prepared surface, rail vehicles are also directionally guided by the tracks they run on...

 usage the conical
Cone (geometry)
A cone is an n-dimensional geometric shape that tapers smoothly from a base to a point called the apex or vertex. Formally, it is the solid figure formed by the locus of all straight line segments that join the apex to the base...

 running surface of the wheel
A wheel is a device that allows heavy objects to be moved easily through rotating on an axle through its center, facilitating movement or transportation while supporting a load, or performing labor in machines. Common examples found in transport applications. A wheel, together with an axle,...

s may be called a rim or a tyre.
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