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| Components of an Alloy Wheel |
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Bolt (Pitch) Circle Diameter / Bolt Hole Pattern
indicates the diameter of two opposite bolts on the wheel hub of a car, and how many bolt holes the wheel needs to fit the hub.
Centrebore Diameter:
For optimum flexibility, ENZO uses reduction rings so that a wheel can have a number of centrebore diameters with only one centrebore hole (basic ring system)
Offset
is the distance from the mounting surface to the rim's true centreline. This measurement is very important as it determines the positioning of the wheel on the car.
Rim Width
is the inner distance between the two rim flanges.
The rim width also indicates the nominal width of the wheel.
Hump:
When strong lateral forces are acting on the wheel (e.g. when driving around curves), the hump keeps the tyre from slipping around on the wheel, thereby preventing a sudden loss of tyre pressure.
There are a large number of different hump designs.
Key wheel indicators:
e.g. 7.5Jx17H2
7.5....Nominal width (rim width)
J.......Size of the rim flange
17.....Nominal diameter of the wheel
H2.... Double hump (individual hump design)
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| Special at ENZO |
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A Wheel Dish with EH2+ Hump
The EH2+ hump is the latest development in hump design.
Together with runflat tyres, the EH2+ hump guarantees that the tyre will not slip off the wheel due to a sudden loss of tyre pressure. Of course, non-runflat tyres can also be used, but without these pluses.
The EH2+ hump is currently is use with our new wheels:
the ENZO R and the ENZO X.
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| Developing Wheel Models |
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The story of a wheel begins with a design idea. Design specification documentation is drawn up outlining the basic definition, appearance and the technical structure of the wheel (one-section, two-section or multi-section). This idea is then brought to life using special CAD software to create the first 3D model for testing.
The software allows the wheel to be turned three-dimensionally and for improvements to be made easily. |
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| Wheel tension testing |
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Spoke stress
Enormous pressure –exceeding by far any actual strain on the wheel in reality – is applied to the 3D wheel model in computer simulations, which calculates tension and warping. The computer also displays the resulting changes in the wheel using different colours. The areas subjected to the greatest amount of stress are shown in red, while stress-free areas are shown in green. |
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 Spoke warping
In this test the 3D wheel model is examined to see if any warping has occurred in the spoke flange. Here again, the critical areas show up in red, and the design modified and corrected. |
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 Final Testing of the Wheel
The 3D wheel model is modified and optimised until the critical stress levels are eliminated. The wheel is designed to withstand enormous loads, guaranteeing safety for the driver and the highest-quality product for us. |
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TUEV Testing
Each and every wheel made by ENZO undergoes TUEV testing as a matter of course, guaranteeing a high level of traffic safety for years. The most important TUEV tests are:
- Fatigue test
- Rolling test
- Impact test
- Test drive
Fatigue Testing
The fatigue test simulates the lateral forces that act on the wheel when it is driven around a curve.
Every alloy wheel is tightly mounted on its inner rim flange using a tension ring and subjected to rotating bending moment throughout the mounting surface of the wheel.
Rolling Test
In this test the wheel is tested for stress performance while being driven in a straight line or around a curve.
Impact Test
This test simulates the impact with a curb stone. A wedge-shaped hammer is used twice to strike both a spoke and the valve.
Test Drive
The test drive involves testing the wheel on every vehicle on the market.
The test also determines offsets, tyres and body modifications.
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| Using Alloy Wheels in Winter |
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Caveat: No wheel is manufactured exclusively for use in winter. A wheel’s suitability for use in winter (resistance to salt and gravel) is determined by the quality and coating strength of the clear finish.
ENZO uses an especially high-quality finish developed particularly to withstand rough winter conditions.
The objective was to strike an ideal compromise between the strength and elasticity of the finish. There are several non-standardised ways test these properties. The toughest test is certainly the Jaguar drop test. A M8 nut is dropped from a height of 4 m through a tube so that it hits the wheel, testing to make sure the finish does not chip. |
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 Protection from salt:
All ENZO wheels must pass the salt-spray test. In this test the finish on the wheel is scratched and sprayed with an acidic solution in a plastic container for about 300 hours. This test demonstrates very clearly how high the quality of the finish is, as the finish opens up, or “blossoms” where the clear or silver finish has any quality defects.
Snow chains:
Snow chains, mounted properly and at the right time, are not a problem for ENZO wheels in principle.
Depending on the vehicle, ENZO pays special attention to make sure that snow chain access is included in the TUEV certification. |
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Cleaning, Care and Storage of Alloy Wheels
Specially designed cleansers and cleaning cloths have been developed for alloy wheels.
At no time may aggressive chemicals, scouring agents or similar substances be used, as they may diminish the appearance of the wheel.
When storing the wheels, e.g. during the winter season, they should be cleaned first and kept in a dry place. |
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Repair of light-alloy wheels
Unfortunately, repair of light-alloy wheels is still very common. This information explains why it would be better to steer clear of the repair of light-alloy wheels.
The following information was obtained from various Internet pages addressing the repair of one-piece light-alloy wheels:
1.) Damaged rims are heated across their entire area and then repaired by means of a rolling procedure.
2.) Subsequent curing ensures that any differences in strength remain within the tolerance range.
3.) The metal alloy on the damaged wheel is analysed, and we can assure customers that the material used in repairs in which parts are welded on or into the wheel will be identical to the original material (alloy, strength, material quality).
We will refute the above statements one by one.
To start with, here is an excerpt from an information leaflet published in March 1999 by the German Association of Tyre Retailers and Vulcanizers (Bundesverband Reifenhandel und Vulkaniseur-Handwerk e.V.). In this case, a badly damaged wheel (localized deformation of inner bead seat caused by shock load, no incipient cracking) was repaired at a "tyre clinic". The wheel was then intensively inspected with the following result:
1.) Machining of the rim beads caused dimensional changes exceeding the tolerance limits, in particular regarding the following functional dimensions: circumference of rim bead, hump circumference, rim flange radius and outer diameter.
2.) At the same level of local load, local heating and deformation reduces energy absorption by approx. 25 % . In practice, this change in material properties results in increased deformations caused by driving over obstacles or over grooved road surfaces such as rail crossings, transversal grooves, etc.
From our point of view, we therefore advise against such repairs
Source: BRV repair of aluminium rims)
On its website, the EUWA (Association of European Wheel Manufacturers) also strongly advises against rim repair in the following words:
"Repair of a damaged rim or disk by heating, welding or addition or removal of material is absolutely forbidden.
No guarantee on repaired parts is acceptable since such changes may introduce additional stresses in critical high-stress areas.
Wear on rim flanges (top of the flanges) can be tolerated up to a maximum of 10 per cent of the initial thickness of the rim material." (Source: www.euwa.org)
After in-depth tests and inspections performed in December 2004, wheel certification experts at TÜV SÜD Automotive agreed with this statement. Further information: www.tuev-sued.de/automotive
Why is "heating" and "welding" or "addition of material" so dangerous?
As a matter of principle, a deformed rim cannot be restored to its original state. Every material changes its properties once the yield point, i.e. the point prior to which a material deforms elastically (referred to as ReH in the diagram), is exceeded, so that the wheel is permanently deformed (e.g. impact). The higher the deformation, the less force is required to cause further deformation (exceeding of yield point (ReH) or ultimate strength (Rm)). Material strength thus decreases! The material properties cannot be restored to those of a new wheel (not even by annealing and recrystallization).
On wheels, welding has several adverse impacts on the material. Firstly, localized heating causes thermal stresses (i.e. the material is subjected to internal stresses in addition to the stresses occurring during operation). Additionally, material composition is changed by separation and crystallization processes (brittling caused by quick cooling, inhomogenity caused by diffusion and the addition of additives). The strength of a welded wheel thus differs significantly from that of a new wheel. Even repeated thermal treatment cannot restore the original properties of the wheel.
With respect to metal alloys, the following can be said:
Determining the alloy composition of cast rims within the scope of repair work is completely impossible. To identify alloy materials and their proportions, material would have to be sampled from several locations of the rim. This would result in complete destruction of the wheel, which would no longer comply with the inspected original state (material sampling).
Even renowned casting technology institutes cannot always accurately identify alloy composition in the melt, as local material composition is largely determined by the casting process. Basically, only a few institutes at universities and research facilities are able to undertake analyses of the melt (composition of cast).
The costs of such analysis considerably exceed the purchase price of a new wheel.
Depending on wheel design and dimensions, cooling rates differ across the wheel area. Mechanical and technological properties (including crystallization rate) are established during the casting process
Additionally, the production of "repair parts" whose material composition is identical to that of the area into which the part is to be welded, is simply impossible. Even if it were possible, it would result in the material changes described above
Conclusion
Every type of interference with the rim material (heating, welding, adding of materials, or even engraving, etching and grinding) results in a change in material properties and invalidates the strength test report. The wheel owner thus loses all rights to liability and warranty claims.
Based on these facts and our responsibility to our customers, we most urgently advise against rim repair even though insurance companies have lately started to push for this type of repair work for cost reasons.
Paint damage:
Only specialist repair shops have the required technical know-how and can restore wheels after paint damage.
Why does AEZ not have any “paint markers” on offer?
In our spray painting facility, wheels are cleaned fully automatically, passivated, primed and then sprayed in silver using wet-in-wet technique and given a protective clear-coat finish. After priming, the paint is baked in an oven. After the wet-in-wet procedure (e.g. silver paint and clear-coat finish), the wheels are also automatically subjected to thermal treatment (baking oven). The silver coat and the clear-coat finish are again oven-baked.
This procedure ensures ideal paint protection against environmental influences (UV radiation, salt, moisture, dirt, etc.) at all points.
A paint marker would bring only "temporary" improvement as it does not offer the same adhesive properties as the baked powder paint, lacquer or clear coat finish. After a short period of using the wheel in standard weather conditions, the paint (paint marker) would gradually chip off or even corrode.
High gloss: This special paint finish cannot be produced with a paint marker. The reason lies in the technical procedure used to produce high gloss wheels. High-gloss wheels are first coated with a black powder, and then oven-baked. After this step, a special silver paint and the clear-coat finish are then applied by means of a special technique which is impossible to manage in a "paint marker".
Should you need any further information, please don't hesitate to contact the experts at AEZ Light Alloy Wheels and TÜV SÜD Automotive.
Contact:
AEZ, Mr. Ing. Pierre Czompo, Tel.: 0043-2256-801-513
TÜV SÜD Automotive, Mr. Jürgen Hübner, 0049-89-32950-693
AEZ Technical Department, 2007 |
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