Despite current temperatures, warmer weather is coming up.
One of the car repair issues that we see a lot of around this time period, is brake pulsation. When we get wild temperature swings, and people are parking hot brakes in 60-70 degree weather that drops to freezing overnight, or people are suddenly driving through cold puddles – we get complaints about that infamous ‘shudder in the car’ while braking.
To understand why this happens, some fundamentals of the braking system need to be understood.
When you hit the brake pedal in your car, you are actually pushing fluid. You’re using brake fluid as a hydraulic connection between your brake pads (if you have disc brakes; shoes if they are still drum brakes), and your foot.
When you push that fluid, it travels from the master cylinder (at the end of the pedal) down to the wheels, creates pressure behind the caliper pistons, and is used to squeeze the brake pads together. If you’ve ever ridden a bicycle, a cars brakes function a lot like those on a bike. You’re squeezing those brake pads against a spinning disc, and the friction generated, drags against the spinning disc until it finally stops.
The thing about brake friction is….. it generates heat. Some heat build up is normal, and brake rotors are designed very specifically to combat that heat. Braking systems are designed around specific metal types, and rotors can have fins and spacing added, to allow for heat dissipation. Often, even the pads themselves are designed with specific materials, from the manufacturer, to dissipate specific amounts of heat.
As these components wear, they break down over time and use. The brake pads wear low, and the material absorbs bits and pieces of road dirt and debris, and small amounts of rotor metal that wears away. The rotors are heated and cooled THOUSANDS of times over their lifetime, and the metallurgy changes. The surface of the rotors wears away, and becomes uneven, or can sometimes become mirror smooth, offering little for the brakes to grab onto.
Another major issue, often the most noticeable wear issue – is when the disc portion of the brake rotors warps. This usually happens well before the brake pads or rotors are actually ‘worn out.’
Picture a record, or a CD. It should be a nice flat surface, correct? Now imagine if you puckered and buckled that flat CD or record all the way around, wavy up and down spots scattered around. Think what would happen if you almost melted it.
That’s what happens when brake systems cannot shed enough heat, or shed it too quickly. When the metal rotors aren’t given enough time to dissipate heat, or that heat is forcibly shed, warps in the face of the rotor occur.
These high and low spots are spinning at the same speed you’re driving; and then you’re squeezing the brake pads against it. The feedback that naturally occurs at this point, is what causes the shake or shudder people experience.
At this point, usually the vehicle is brought to a repair shop, and a brake inspection is performed. If a qualified technician is working on the vehicle, and the shop in question is trying to give you the best value for your repairs; there are specific things they should be checking with every brake check.
Of course, the actual thickness of the brake pads, brake shoes, and/or parking brake shoes should be checked.
However, this is where some shops do a disservice to their customers. When brake pads are worn, they have a matching wear pattern that they have rubbed and scrubbed into the rotor face as well. Some repair shops will replace the brake pads only, and force the new, flat pad surface, to try and grab against the old, worn, grooved, and uneven rotor surface. This causes strange pad wear, noises, and sometimes worse issues by making the brakes stick or not grab enough to stop the vehicle properly.
A correct brake inspection will include a surface measurement of the brake rotors to check for how warped they may be, how grooved they are, how thick they are (which affects how much heat they can handle), and also whether they have been too hot or cooled to quickly (the shop will check for heat markings, or blue-ing that can indicate a process called ‘annealing’).
If the shop really has your best interest in mind; they will be inspecting the condition of the brake caliper at each wheel, each brake hose, and all the other small moving parts. This prevents you from replacing pads & rotors and having them worn down by another failed part, that causes them to prematurely wear.
If the vehicle has parking brake shoes that are hidden inside the regular brake parts, they will advise you before work begins, that they may find more parts in need of replacement. A good ‘worst case scenario’ should be quoted, so that you can be prepared for possibilities, once they take the rest of the braking system apart.
The goal of an auto repair shop at this point should be to help you have all the information, to make a good decision, on what repairs need to be made, and what can wait. Routine maintenance should be explained, and offered, but safety issues should be prioritized. Other unrelated issues seen while a technician was looking the vehicle over should be explained in the same way, presented to you with a focus on safety first, pressing repairs or catch-up maintenance next, and future needs you can plan ahead for.
If they are really focused on providing the best value to you; they will be able to include services in packages, perhaps you will save on labor. Some repair shops may also be able to bundle maintenance in with your brake repairs that extends the warranty period. These are things that benefit you, as a driver, in the long run, by providing better protection coverage for something that is guaranteed to wear. If you can spend a little money at the time of repair, to prevent completely re-paying for the repair in the future; it’s definitely good value.
So when you feel that steering wheel shake the next time you hit the brakes, be searching for a place that knows and understands brakes; can properly inspect them, and has a servant’s heart mentality, where they want to keep you, and your vehicle safe, and stopping properly.