Sometimes the simplest ideas can have the biggest impacts.
Brake squeal is an annoyance we've become accustomed to, with Porsche even explaining in a video that it isn't a bad thing (seen below), but Ford has figured out how to get rid of it almost completely, using an idea so simple, the brake manufacturing industry is going to kick itself for not discovering sooner.
CarBuzz has discovered a patent filed with the United States Patent and Trademark Office in which Ford details a cutout or notch in the brake pad's outer edge that stands to reduce brake squeal dramatically. The patent goes to great lengths to detail why brake squeal occurs (tangential nodes, for the record), but the Porsche video explains it pretty well. Essentially, brake squeal is caused by resonant frequencies vibrating the brake rotor in a certain fashion, more prominently occurring in cars with larger brakes, like a Ford Mustang Dark Horse. So how does Ford's new pad design eliminate this?
Well, in cars with larger brake rotors, the pad surface is also pretty large. The larger the friction surface, the more friction can be generated, slowing the car better. A traditional brake pad is typically rectangular in shape with a curved outer edge that fits along the edge of the brake disc, maximizing the effective friction zone. But Ford's new pad design takes a notch out of that curved edge.
Ford has identified the outer edge of the disc as having a “potential for high modal displacement in a tangential direction,” or basically being susceptible to the vibration frequencies that would cause brake squeal if that edge were to be contacted by the pad under braking. The larger the diameter, the higher the likelihood of brake squeal, as this increases proportionately to the brake diameter.
USPTO USPTO
By cutting a notch of 7 mm deep, Ford's simulations suggested a vastly reduced likelihood of brake squeal above an accepted level of 70 decibels compared to the standard pads, which frequently hit 88 dB. But by making that notch slightly larger (10 mm), Ford was not only able to avoid the two instances of squeal from the 7 mm notch but reduce noise levels substantially, with a maximum volume recorded of 54 dB. The results of these tests are visible in the graphs below.
Ford proposes notches of at least 8 mm as being ideal for reducing brake squeal. And, because the notch occurs where the pad is at its meatiest in height, the minimum height of the pad is never brought below that of a standard pad design.
Not all brake squeal results from these vibrations, and pad wear can cause brake squeal too. But with Ford's new patent, at least squealing brakes will only be the result of worn pads and not just general use.
Keyword: FINALLY! Ford Eliminates Brake Squeal With New Brake Pad Design