Myth Braking

We’re not really ones for rocking the boat. But when we see local prices for parts that are completely unjustifiable, we think it’s only right for us to do what we can to correct that. At the same time, when we see our industry purporting things which are untrue, we want to do what we can to dispel the myths and provide some insight to help our customers form their own opinions. Brakes are a contentious issue. Nobody wants to compromise on their own safety or the safety of their family. So when a mechanic says something needs to be done to the brakes, most people are happy to just get it done, no questions asked. Warped brakes are a term that’s thrown around often, but it’s not something that is well understood by drivers.

Shudder

Everyone will experience brake shudder at some point. Brake shudder can either be felt through the steering wheel or through the brake pedal itself. During light braking at low speed it’s actually possible to feel the contact point hit the brake pad as the rotor turns. It’s an especially common symptom on modern cars, with the solution being to either machine (or ‘skim’) the discs, or replace them with a brand-new set of rotors completely. The shudder is almost always attributed to warped discs. Despite being so widely accepted throughout the automotive industry, warped discs are a myth. Warped discs are an easy explanation to a complicated problem, but one that is so often accepted simply because you can sometimes feel the ‘potato chip’ effect under your right foot. But it’s not quite as simple as it seems.

Causes

Most common brake rotors are thick cast iron, making them extremely strong and durable. It would take significantly more heat and pressure than what is possible with a standard braking system to make cast iron soft enough to reach the point of being susceptible to warping. Brake pads, however, are not as tough. A composite friction material, brake pads convert motion into heat. Every brake pad has a different effective working heat range. Racing pads can withstand extreme temperatures, but must have a lot of heat in them before they work correctly. Normal street pads have a low working heat range, but become far less effective when they are heated beyond that working range. Because of the heat absorption of the disc during hard braking, it can cause pad material to melt onto the disc when the vehicle has stopped. With the brake pad clamped onto the extremely hot disc, it creates what is known as a hot-spot, leaving behind pad material on the rotor. Although the pad material left on the rotor is only a few microns thick, it creates an uneven surface which is amplified by the hydraulic braking system. This is what causes the shuddering that the driver experiences.

Fixes

Prevention is always better than cure. Correct bedding-in procedures when installing brakes will treat both the pads and the rotors, helping to avoid the issue later. You can read our article on brake bedding-in procedures here. Bedding-in creates a uniform ‘transfer layer’ on the rotor. Typically city drivers will experience brake shudder more than country drivers, as their driving conditions demand a more aggressive braking style. Braking harder and later can lead to hot-spots on the rotor, whereas doing the majority of the braking earlier will help keep the temperatures down and the transfer layer consistent. Being careful not to clamp the brakes hard once you’ve come to a complete stop and by inching the vehicle forward, you can avoid hot-spots from developing. If you do find your vehicle developing a shudder during braking, you can follow the bedding-in procedure for new brakes. This can help remove pad material from the disc. Of course, machining the disc will remove the material and create an even plane across the rotor, but this can significantly reduce the life of the disc at the same time. As some service centres charge labour as well as a fee to machine the brakes, it can often be cheaper and quicker to just replace the rotors altogether. Whatever you decide to do, at least you can go forward with a better understanding of the complexities of brake wear and the causes behind brake shudder.