Rim (wheel)

As a car rim is called colloquially the wheel of a car without tires. In the strict sense refers to the rim only in the outer ring, which is connected through the wheel rim with the wheel flange. Today, however, these are mostly manufactured for passenger cars in one piece, resulting in a linguistically factually not completely true synonymy of wheel and rim yields (which similarly for tire and wheel applies ). Only for commercial vehicles such as tractor special truck ( tractor) and some special applications (motorsport) there is composed of several parts assembled wheels.

Materials

Car wheels are made today are either made ​​of rolled steel or cast light metal or forged. Steel wheels are usually cheaper, but are visually less appealing than most alloy wheels. In some cases, the unsprung mass reduces the use of alloy wheels, the suspension response is better. Since today, however, high-strength steels are used, which make do with correspondingly lower wall thicknesses, the weight advantage is currently being frequently changed in favor of the steel wheel. The commercial vehicle wheels made ​​of cast steel (carbon or Kevlar carbon fiber or aramid fiber reinforced plastic, colloquially known ) are often used in motorcycles, however, even those made from fiber composite material.

Steel wheel

The most commonly used steel wheel is a so-called disc wheel and is usually out of the rim itself and the wheel disc or wheel disc. Today's wheels are manufactured from hot rolled steel with high yield strength (> 600 MPa), the wheel disc as well. Both are welded from the inside sections, because the component would be forgiven with continuous weld. The position of the weld seams is selected so that the driving load for the dynamic exposed (when viewed in cross-section) not changing bending stress. Vital at this point - - fatigue strength ensured, which is especially critical in welds Thus is.

Alloy wheel

Alloy wheels are usually charge only features. However, they are mainly for vehicles of premium car manufacturers, but also increasingly in (special) models of cheaper brands to the factory standard. They are usually made ​​of aluminum, rare magnesium alloys (Formula 1, Rally and expensive sports cars ) in the casting process and provided with a special paint. A distinction is made between cast and forged wheels, and the Alubandrad ( disc wheel, steel wheel construction as of rim and disc ). A forged aluminum wheel is lighter than a correspondingly produced by casting wheel be due to the higher strength of the material. The microstructures are not disrupted in the manufacturing process and the material is strain-hardened by the deformation to a great extent. It can be distinguished even one piece of multi-part wheels here. One-piece light-alloy wheels are made of a single piece of metal, while multi-piece wheels, for example, consist of the rim and the wheel disc, screwed together or welded. Usually light-alloy wheels in the production process with a matt silver lacquer coat and a clear coat (mostly in the powder coating process ) coated or less often with a darker finish, possibly in body color. So-called chrome alloy wheels that receive a high-gloss surface by electroplating instead of a coat, enjoy especially in the tuning scene and more popular.

Alloy wheels usually offer no improved performance, greater security and comfort; they serve the appearance of a vehicle. If wheels are especially light construction, such as magnesium wheels to reduce unsprung weight, which affects the driving behavior favorable. Rarely, the cooling of the brakes (larger air permeability compared to a typical steel wheel ) improved, which is why some car manufacturers prescribe alloy wheels for summer tires, rare even for the winter tires. If the brake system require a rim of at least 18 inches in diameter, as is the case for example with some current sports cars, there is only the possibility of using light-alloy wheels even with winter tires. In older vehicle certificates, there was a note, if only alloy wheels may be used, which was also made ​​between summer and winter wheels.

The problem is the corrosion resistance especially at low-cost light-alloy wheels. Especially wintry weather conditions and connected thereto, the use of the scattering materials icing, sand or grit can cause damage in the paint layer and thus corrosion. In recent years, however, are increasingly being special "Winter Alloy Wheels" offered. These are characterized by an increased in comparison with standard alloy wheels shock, impact and scratch resistance of the coating, and thus an improved corrosion resistance.

Be used unless specified by the manufacturer of a motor vehicle for the type "original " alloy wheels, admissibility is directed on the road on whether this a general operating permit (ABE) included or whether they were entered in the vehicle documents.

Aluminum wheels if the degree of damage, it allows to be repaired. First and foremost, only two - or three-piece wheels can be repaired. Here, the exchange occurs outside of the bed or inside the bed. Is particularly important in the performance of the repair, the wheel bolts to replace because they are designed as expansion screws. The use of old rims screws (these are usually designed as M7 screws) is not permitted. By wheel repair deal now numerous companies. Solid wheels can be treated only superficially ( polishing the surface). In cases of major damage and ( deep ) cracks, however, replacement of the rim is inevitable. Modern rebuilders work in determining the damage often -ray equipment.

Special shapes

An almost standard special type of commercial vehicle rim is the Trilex rim, which is peripherally divided into three unequal segments. During a wheel change can (like the wheel disc at the car) left on the bike so the wheel spider, only the actual rim ( in this case, also sometimes called " rim ") must be dismantled.

Pictures

1950s: chrome hubcaps ( NSU Sport Prinz )

Spoked wheel with central locking of a roadster of the 1960s (Austin- Healey )

Alloy in the 1960s (Ferrari)

Mercedes -Benz hubcap of the 1970s and early 1980s made ​​of stainless steel, some painted in body color

1970s: Stahlsportrad a VW 1303 Cabriolet

Classic Mercedes -Benz light-alloy wheels ( " baroque wheel ", forged by the Otto Fuchs KG ) 1968-1985

Red lacquered light alloy wheel in the Porsche 996 GT3 RS ( 2003)

Usual silver colored plastic wheel

Wheel made of CFRP ( carbon fiber reinforced plastic) Manufacturer: Arthec carbon bike GmbH

In chrome-look coated alloy

Modern alloy wheels with central locking (Porsche 911 built in 2009 )

Measurements

Car Humpfelgen are standardized in DIN 7820 DIN 7817 and commercial vehicle (CV ) rims.

Decisive for the tires to be used are mainly the diameter and the width of the rim.

• The rim diameter is determined between the rim shoulders. It corresponds to the inner diameter of the tire to be used and is given as inch code.
• The rim width is measured between the rim flanges ( the padding ) and also known as mouth width.

Whether a wheel can be mounted on a vehicle depends on number of holes and pitch diameter of hole circle, the diameter of the hub bore and the Offset:

• The number of holes with which the wheel is screwed, at least three, but usually four or five; off-road vehicles or trucks more (except central locking with wing nuts like the Roadster in the picture above).
• The bolt pitch circle ( ) denotes the diameter in mm of the circle on which lie the centers of the screw holes.
• The central bore, the central bore, with which the wheel is placed on the wheel flange.
• The offset (ET ) is the deviation between the wheel center and the inner contact surface of the wheel disc to the wheel hub (called mirrors), so the brake drum or brake disc on. It is measured in mm. Is the Offset 0 mm, the wheel is located in the symmetry plane of the tire on the brake drum. If it is greater than 0, ie, a positive ET, the wheel extends further inward, that is, the track width (measured from center of tire to center of tire ) is smaller. With a negative ET the track width is increased and the wheel moves further outwards.

Instead of the abbreviation ET some manufacturers use (eg Ford) also the abbreviation OS ( = offset).

• Also the diameter of the holes in the bolt pattern is critical, such as Mercedes -Benz and Volkswagen use for transporter wheels with identical dimensions, but the mounting screws have been in a case 12 mm, but 14 mm in the other thread. Light-alloy wheels from Mercedes are well on VW vans can not be used because the mounting screws do not fit through the holes.

Example of car wheels name:

• 7 ½ J x 16 H2 ET15, PCD 5 × 110 MZ57 7 ½ = mouth width code ( rim width ) corresponds to the rim width in inches (from the inside of the rim flange to rim flange )
• J = name of the rim flange ( here: Form J, corresponding to a height of 17.3 mm), other versions: H, P, K, JK etc.
• X = designation of a one-piece drop center rim ( × is now spoken as " times ", originally the speech "X" was provided ), other version: - (pronounced " slash" ) refers to a multi-part flat base rim
• 16 = rim diameter code corresponds approximately to the rim diameter in inches (measured at the bead seat )
• H2 = hump in this case both sides of ( 2) (prevents Reifenabrutschen into the deep bed when cornering )
• ET 15 = Offset is positive ( ) 15 mm (with negative ET is the minus sign in front, for example, ET -15 )
• LK = bolt circle of the wheel
• 5 x = number of the bolt holes
• 110 = Diameter of circle of holes in mm, which runs through the center of the mounting holes
• MZ = hub bore or Mittellochzentrierung (MZ ), called here as an example 57 mm diameter

Vehicles have different hub bores. Alloy wheels in the tuning range have larger holes in the rule. By means of a centering ring (made of plastic ), the difference in diameter of the wheel is matched to the vehicle. Steel wheels are available only with the same bore diameter as the vehicle.

Thus, the indication referred distributed on a circle of 110 mm diameter a wheel with one-piece drop center rim with Doppelhump, 7.5 " rim width, 16 " diameter, a rim in J- version, a positive offset of 15 mm and 5 mounting holes. The Humpausführung suggests the usefulness of tubeless tires, but is not mandatory.

Installation of car wheels

Car wheels are dismantled before so that the wheel nuts or bolts loosened, then lifted the vehicle and the wheel nuts or bolts then be dissolved. After that the wheel can be removed from the wheel hub and the new wheel will be mounted in the reverse order of operation: In most cases the wheels are balanced by mounting the tire prior to mounting on the vehicle. It is helpful to a so-called centering to accurately put the wheel back to screw onto the wheel hub. To install the screw usually tightened after inserting the wheel bolts and lowering the vehicle with impact wrench or a torque wrench, with the respective tightening torque of the manufacturer must be observed. Are the mounted wheels not original parts of the vehicle manufacturer, they require either a general operating permit (ABE ) of the Federal Motor Transport Authority, whose number is specified as KBA number on the wheel. Or the wheels must be registered by an officially recognized expert in the vehicle documents. The use of wheels or without ABE registration will invalidate the approval of the vehicle and disorderly.

Speedometer

A tachometer measures the speed of the car wheels and calculates the (theoretical ) speed of the car ( neglecting slip). If the rim is changed to a different diameter, it must be ensured that the rolling circumference of the wheel still remains the same. This can be achieved by choice of a different tire section. Succeed this adjustment only insufficient, is no longer correct the indicated speed, which should be solved by a speedometer adjustment.