It is pretty standard. We get in our vehicles and we turn the key–or push the button now–and drive. We never really stop and think about all of the mechanics involved in keeping everything working in harmony. In this article I want to introduce you to your brake system. It is more than just the pedal on the left, and I want to do it in a way that doesn’t over complicate or over simplify the system. Recently, a client wanted to know more about calipers, specifically and I thought maybe you would too. So, first stop: the pedal on the left.
Your car’s brake system operates using pressure generated from brake fluid. While you may press the brake pedal with your foot, that foot pressure is converted to hydraulic pressure. The brake fluid is diverted between the front and rear of the car and distributed to each wheel.
Using a test strip, the technician samples the brake fluid. The tip of the strip changes color. The darker the color, the more contaminated the fluid. 
It is important to have the proper type of fluid, the proper fluid level, and clean fluid in your brake fluid reservoir.
Your stopping power, or how effectively your brake system works is determined by the clamping force of your calipers. The brake fluid, now pressurized and passing through the brake hoses to your brake calipers now push the brake caliper piston against the brake pad causing them to clamp down against the spinning rotor, slowing it down and forcing it to stop rotating. The brake caliper pistons come out of a hollow cylinder (you might laugh at me right now, but think push-pop…) As your car’s brake pads wear down naturally over time, the pistons become nearly fully extended.
Outboard View of a Brake Assembly. Circled is the Brake Caliper Assembly 
Inboard View of a Brake Assembly. Circled is the Brake Hose. The arrow is pointing to the Brake Caliper Assembly
In order to replace the brake pads, the brake caliper pistons would have to be retracted. Using improper tools and forcing the pistons back into their cylinders causes damage to your braking system. Some may be threaded and would have to be wound in, some are electronic and require a computer to retract them. In any event, as a professional I try not to cringe when someone has done their own brakes–without the proper tools it could lead to caliper damage.
A brake caliper that could not be saved. Yes. Yes we can stop that noise. Now you can stop too. 
The top brake rotor starting to glaze from excessive heat. The bottom brake rotor has rust ridges where the brake pad does not make contact.
Your car’s braking system has a few other moving parts that make you stop. Like the pistons, you may also have caliper slides (some are piston-only systems). In a piston and slide type caliper, the way your brake pads wear tell us how your brake system is failing. When we perform a brake inspection, we are not only looking at your brake fluid level, brake fluid condition, brake pedal height and operation, and measuring your brake pads and rotors, we are also comparing that information from side to side as well as inboard to outboard. Let me translate.
I had a client who recently brought in a 2018 Jeep Wrangler. It had just over 24,000 miles on the odometer. The tires were rotated by a local dealer and the client was told the rear brakes were at 4/32″ and should be changed soon. That was all true–2/32″ is considered discard and I would make the same suggestion. However, I found something quite odd with the overall recommendation–I knew that the likelihood of the rear brakes wearing out before the front brakes were rare and their was an underlying problem. We needed to dig further. The front brakes were still practically new and had in fact never been replaced. We measured the inside (inboard) and outside (outboard) pads–front and rear. There was a discrepancy in the rear–they were not wearing evenly. The right rear wheel was excessively hot. The rear caliper on the right side had failed. While brakes are considered a wear item and do not fall under factory warranty, calipers are not. My client received new calipers and brakes under warranty because I could interpret what the wear pattern meant.
Your car’s braking system has a lot of fail-safes built in to prevent premature wear. Dust covers on the calipers over the pistons, dust or debris shields behind the brake systems, dust boots over the brake caliper slide pins–all of those are geared to keep dirt and debris out of the braking system. Once dirt or road debris infiltrates the brake system, say on the polished surface of the piston, the continuous back and forth motion already creates friction. Now you have an abrasive friction and a perfect storm for a leak scenario. Tying back in to my opening, this is a fluid based or hydraulic system. Fluid loss equals pressure loss in the sense that your brakes can no longer build up enough piston force to push the pad against the rotor and stop your car.
So, here is the deal. I care. I care a lot. I want you to look out for a few things. If you hear a squeal or squeak, please don’t turn up your radio–well, make a reservation to get the noise checked and then turn up your jams. If the brake pedal feels different–drifts to the floor, feels spongy, feels hard, pulsates–it is time for a brake inspection. If your car pulls to one side or the other when you brake or the steering wheel shimmies a bit–let’s get you on the schedule. We do have a very small fee for our brake inspections, but we do apply it towards the repair. I have great specials on my website: http://www.aanthonys.com I want you to be safe. Especially with the holidays right around the corner. Stop by if you can. You’ll be glad you did!
Grease In Her Veins 