SINSHEIM-DÜHREN, Germany — The manufacturing process for brake discs at Zimmermann involves several essential steps: The cast blank is turned on a lathe and the hole pattern is drilled in the hub of the brake disc. The brake discs are then balanced and a special heat-resistant aluminum coating is applied for protection against corrosion.
Manufacturing differences in brake discs are not always easy to spot. This makes it all the more important to know the criteria that define a quality product.
In the field, Zimmermann staff repeatedly encounter products by other brands, that have been manufactured with inferior precision and fewer steps than required.
For example, upon closer examination, some brake discs turn out to have not been balanced. According to ECE specifications, balancing measures must be equivalent to those used for the original-equipment (OE) part.
To the untrained eye it is not immediately obvious whether or not brake discs have been balanced. If a brake disc is balanced can be determined by the milled groove. At the point at which an imbalance is detected, material will be taken away very precisely (to within 0.5 grams).
Other balancing methods, such as adding weight by inserting wire clips into the ventilation channels, have become obsolete over the decades and are almost never seen in today’s aftermarket. However, there are now manufacturers who skip the crucial step of balancing altogether.
Due to the casting process, ventilated brake discs feature areas that cannot be machined or turned – for example inside the ventilation channels. To compensate for these inherent imbalances, a precise balancing operation is indispensable.
What happens if an imbalanced brake disc is installed?
An increased level of imbalance creates a radial runout that can result in vibrations in the steering wheel and across the entire vehicle. The intensity of these vibrations varies depending on the vehicle speed and affects wheel traction as well as driving comfort and ultimately – safety.
In the long run, damage to wheel bearings or the entire wheel suspension is likely. In the case of imbalanced brake discs for the front axle, the control arms, pull bars, push bars and the strut bearings are particularly affected.
To avoid these types of complaints following installation of new brake discs, it is important to make sure, prior to installation, that only quality brake discs are used and not products that only seem good at first glance.
