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RadCarsten

RadCarsten

Here our wheel expert answers the most frequently asked questions about light alloy wheels. Your request is not included? Contact RadCarsten directly via e-mail: radcarsten@borbet.de. He will gladly help you.
Aufbau einer Leichtmetallfelge
wheel rim width
This indicates the breadth of the wheel rim. The measurement specifies the distance between the inner and outer rim edge.

offset
The offset is determined by the distance between the centre of the wheel and the wheel contact surface. The offset value indicates how far to the outside or inside of the wheel the hub is located.

pitch circle diameter
The bolt circle is the diameter of the circle that passes through the centres of the lug holes. The bolt circle is measured in mm.

centre bore diameter
The centre bore diameter is often reduced using centring rings, rather than corresponding to the size of the actual hub itself. This allows wheels with the same bolt circle to be used on a very wide range of vehicle brands. Many wheels for widely sold vehicles (Audi, BMW, Mercedes, Seat, Skoda and VW) also come with centre bores which are a snug fit for that particular vehicle.

Wheel hump
The wheel hump refers to the beading on the wheel rim which prevents the tyre from slipping into the rim well when experiencing transverse load, such as during high-speed cornering.

Aufbau einer Leichtmetallfelge
KBA number
A KBA number is issued by the German Federal Motor Transport Authority in Flensburg. On all BORBET specialist trade wheels, this number can be found on the outside near the ventilation hole. The KBA number guarantees that the wheel is a “standard manufactured part”. This means you can be sure that there will be no issues with the TÜV registration even after several years. The KBA number is also the basis for the Vehicle Type Approval – without a KBA number, a TÜV registration would need to be undertaken.

Technical component report, TÜV assessment, Vehicle Type Approval
There is a huge difference between a technical component report and a Vehicle Type Approval: If a Vehicle Type Approval is in place (as is the case with 99% of our wheels) and the corresponding tyres do not need to be amended, then it is not necessary to acquire separate expert approval. However, if conditions such as “tyre tread coverage” must be observed, then even wheels with Vehicle Type Approval need to be registered. If a wheel “only” has a technical component report, then they need to be registered without exception, even if there are no other requirements to fulfil. However, even technical component reports have their benefits, especially for guaranteeing quick TÜV approval for new vehicles with a component report, as opposed to a complete update to the Vehicle Type Approval.

TPMS
Since 1 November 2014 all new vehicles must be fitted with a tyre pressure monitoring system. In doing this, a distinction must be made between a direct and indirect system. While the latter solely measures the tyre pressure across the rolling circumference, direct systems include special sensors which are installed in each wheel. These sensors are available from many manufacturers on the market, with 99% of them compatible with our product portfolio.

ECE
An ECE number is issued by the German Federal Motor Transport Authority in Flensburg – as is the KBA number – and can be seen embossed on each ECE-approved wheel in such a way that it is visible from the outside. ECE-approved wheels precisely fulfil standard wheel requirements in terms of rim width and offset, as well as the inner contour (for brake release), and as such can be used as they are. They do not always use centring rings and often use standard mounting components. There is NO requirement to carry type-approval certificates/ECE systems.

CoC documents
Certification of Conformity documentation includes all tyre and wheel sizes released by the manufacturer for a particular vehicle. Since October 2006, most newly issued vehicle registration certificates have only included the wheel and tyre combination, which is checked when the vehicle is sold. All other permissible wheel and tyre combinations can be derived from the CoC documentation.

Which tyre sizes am I allowed to have on my vehicle?
The tyre sizes that can be fitted are listed on the attachment to the Vehicle Type Approval/ECE documentation. Only standard tyres are included in the ECE documentation while several other tyre measurements are listed in the Vehicle Type Approval (which is often supplementary to ECE). Whether a specific tyre size needs additional TÜV approval can depend on the width or even the offset. However, many tyre sizes from a Vehicle Type Approval can be used WITHOUT TÜV registration, even if the size is NOT listed in the vehicle/CoC paperwork.



Radwechsel
Assembly instructions (tightening torque, screws etc.)
You can find our assembly instructions on the Multiflex packaging for example, or as a PDF here. You can also find information on the mounting materials required (including tightening torque) in the corresponding report/Vehicle Type Approval documentation.

Snow chains
You can also find out whether it is possible to use snow chains on specific tyre sizes in the report/Vehicle Type Approval documentation under the conditions section.

Cleaning, maintenance and storage
We recommend using warm water and a soft sponge to clean the wheels. Wheels should be stored upright or hanging when being put into seasonal storage, but should not be stacked on top of one another.

Note on repairing light alloy wheels according to the German Federal Ministry of Transport, Building and Urban Development, repair work on damaged light alloy wheels should always be refused due to roadworthiness.
Repairing includes any interference in the material structure, heat treatment and shape recovery – for example removing bulges, sealing fissures in the rim well or application of material after substantial contact with the curb. Repaired light alloy wheels are inherently dangerous and should not be used on public roads!

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