July/August 2020

JULY/AUGUST 2020 AFTERMARKET 31 www.aftermarketonline.net deceleration, by operating the electric motor as generator. Even though the recuperation potential is subject to limitations in future cars, much braking will be carried out by regenerative deceleration. Consequently, the standard friction brake will be used less frequently. “Brake systems should be designed in line with new demands that are caused by particularities of future vehicle generations. Brake noise, vibration and harshness (NVH) can play a critical role for the customer, especially in the premium segment of the market. In electric cars, the situation is particularly critical, due to a lower level of ambient noise. Meanwhile, In the electric vehicle, reducing residual drag is more important than in a standard car because of its impact on the energy balance of the vehicle.” On the need for different materials, Mario observed: “Since used less frequently, special attention is required to avoid excessive corrosion of brake discs and pads. In addition, high and stable friction coefficients must be guaranteed, even if the brake system has undergone long phases of inactivity.” He concluded: “Putting all of these potentials and challenges together, it has become clear that wheelbrakes should be specifically developed for electric vehicles, leaving lots of innovation potential in the field of corrosion avoidance, friction materials and lightweight design.” Silent running As vehicles have become quieter, and in the case of EVs and hybrids, very quiet indeed, the issue of brake noise has come to the fore. Stefan Bachmann, Team Leader for the MEYLE brake and drive product area said: “We note a clear trend towards sensitive perception of sounds. This is easy to understand, especially with regard to the electromobility. By eliminating engine noises, the driver becomes more sensitive to noise in the vehicle, so that previously unnoticed brake noises can now be perceived. “A squealing brake does not always mean a broken brake pad or disc. First and foremost, it must be said that there are actually brake systems with mechanical wear contacts. Instead of a message in the cockpit about the wear, a squealing noise is heard when braking. As a rule, the sportier the brake pads are, the more they tend to squeal. In the case of sporty drivers, higher loads can result in stronger vibrations between the brake pads and the brake disc, which can be perceived by the driver as disturbing or squealing in certain frequency ranges. In addition, 'neighbouring' components such as control arm bushings are worn out and vibration is transmitted in the direction of the last component of the overall suspension – the brake. Nevertheless, a squealing brake can of course also mean that there is a fault in the brake system or that incorrect brake components have been installed.” Style According to Stefan, driving style can have a big impact: “The classic driver places a lot of emphasis on comfort, whereas the sporty ambitious driver attaches greater importance to performance. “While the MEYLE- ORIGINAL brake pads focus on the lowest possible background noise for the ‘comfortable’ driver, the MEYLE-PD brake pads clearly focus on performance for sporty driving and tight response. “With the new MEYLE-PD brake pads next generation, we have succeeded in combining the best of both worlds, resulting in performance- oriented, low-noise brake pads that also cause significantly less emissions. This not only helps the environment, but also makes rims cleaner for longer. “For the MEYLE-PD brake pads, we have adapted the friction material and further developed it technically. The design of the brake pads has also been adapted; Chamfer and slots of the friction pad are optimally and individually aligned to the different vehicles.” Stefan added: “The new MEYLE-PD brake pads have individual so-called shims, between three and five layers depending on the application, which decouple vibrations in the best possible way and thus further minimize noise development.” Judder Brake problems maybe more common at present. Under-use, as seen under lockdown, is not great for brakes. Colin Cottrell, Marketing and Central Operations Director at LKQ Euro Car Parts observed: “If left for a while, a vehicle’s brake discs can begin to corrode, because there’s no motion to stop rust from building up. This can contribute to brake judder and can eventually lead to the brakes seizing up entirely, all of which mean the vehicle must go into a garage for repair. On how to deal with seized brakes, Colin commented: “After checking all the relevant components and removing the brake discs, use appropriate tools to thoroughly de-rust the contact surfaces and hub edge. A purpose-made hub grinder will speed up the job and reduce the chance of hub damage. Witness marks on the back of the disc face are a sure sign of issues, particularly if uneven contact and rust is evident. Use a good brake cleaner to clean the bright metal contact surface. “Once the brakes are totally flat and clean, it’s important to measure brake disc thickness variation. In our experience, this is the most often overlooked part of the diagnostics and repair process. It should be carried out every time, to ensure nothing is missed, as even the tiniest spec of dirt or rust can mean that the disc wears unevenly. “Use a dial gauge to measure the lateral run-out 10-15mm below the maximum radius of the disc. We recommend that the maximum disc run-out is 0.07mm. If the hubs are clean and you’re still getting readings higher than this, remove the disc and use the dial gauge to measure the hub run-out. This should be no greater than 0.03mm. Colin added: “Providing a complete service is the best way to ensure customers are happy when they leave your workshop, and to drive repeat custom. They might have come in complaining of brake judder, or have visibly corroded brakes, but we recommend checking their brake fluid while they’re with you.” Above: Directional brake pads from Delphi Technologies