Have you ever wondered what exactly is involved in stopping your vehicle? Whether it is small or large the basic components and principles of stopping the vehicle are the same; however, there are two different sources that power the brakes, hydraulic (which uses liquid under pressure) and pneumatic (which uses air under pressure).
Hydraulic brakes function:
When the driver applies pressure on the brake pedal in the vehicle, the pedal then depresses a cylinder that is dry on the pedal side and is attached to a small reservoir of fluid that has four ports built into it; two ports on each side. When the cylinder gets pressure from the driver, it compresses the fluid through the ports down these small diameter steel lines all the way to each tire. If the vehicle has disc brakes, those steel lines connect to two small pistons inside of a housing called brake calipers which push up against two metallic pads; one on each side of the rotors(round metallic disc) which then squeezes the rotor to slow the wheel down.
Now drum brakes on the other hand, are mostly found on large trucks, buses and large trailers and various older automobiles on the rear axles only. If it is a hydraulic system, those steel lines come into the wheel and connect to a single slave cylinder which has two plungers sticking out of both sides.
When the driver pushes the brake pedal the fluid forces the two plungers outward to the edge of the drum to push two brake shoes; one on each side to rub up against the inside of the drum which then in turn slows the wheel down.
Now that I have put you to sleep while explaining hydraulic brakes with a more than detailed version of Wikipedia, the air brakes are basically the exact same as the hydraulic drum brakes with the exception that there is no fluid whatsoever involved. There is a booster cylinder attached to the brake pedal that has air lines connected to it and air lines that run to these round metal chambers with rubber diaphragms inside of them. Attached to the diaphragms, is metal linkage or a slack adjuster which connects to a spinning shaft or cam that goes into the drum assembly of each tire. At the end of each cam there are fingers that grab both brake shoes when the pedal is depressed to force them outward into the inner drum.
Why go into so much detail in a blog about functionality of brakes, we are passionate about educating any and everybody that wants to become more self-efficient in whatever facet of life they can. While we cannot explain how to perform medical procedures on one’s self, we can try to help with the basic day-to-day things that we all rely on like maintenance on our vehicles.
We want to also give you 5 simple items that you as a car, truck owner can check or keep an eye on with your brakes:
- Hydraulic brakes should always have fluid in the master cylinder which is usually located directly under the hood up against the firewall on the driver side of the vehicle. Most car systems will use DOT 3 brake fluid. If you are unsure as to what fluid it needs, please contact an auto parts store with your make, model, and year. Many times we have found that if you take your V.I.N. to them it is much easier. This 14 digit number is easily found on the sticker of your driver door or on a metal tag located at the bottom of the dash behind the steering wheel. If the vehicle is getting up there in mileage like in the 200,000 mile range the brake fluid should be replaced with new. We can go into that procedure in another info blog.
- When you are looking under your car or truck, check all around the inside of the tires to see if there are any signs of oil seeping which could easily indicate a leaking brake cylinder or inner wheel seal. It’s always a good idea to look at the tires and wheels on a regular basis to make sure everything is intact anyway.
- While you are laying on the ground taking a nap under your vehicle there is a quick way to check if your brake pads or shoes are not worn dangerously thin. On disc brakes which are usually found on the front steer tires unless it’s a newer model vehicle, turn the wheels pointing out and you can look inside of the brake calipers to view both pads at the same time. If the friction material is the thickness of a nickel coin or less, they need to be replaced ASAP. On drum brakes, many people will say, “All you have to do with those is just lay down on the ground and pop out the little rubber plug on the small 2”inspection port located at the lower back of the drum to see how the shoes are wearing”. We are here to tell you unless you do well at the casino, you will not get as good of a reading through that little hole that you couldn’t put a peanut through. Most of the time, you need to remove the tire and pull the outer drum off of the axle to inspect thoroughly the shoes.
- On Air systems, get out and inspect basic items that are easy to see more commonly; such as air lines, chambers and slack adjusters. Those are the items that will always wear out the quickest. Make sure metal isn’t cracked or loose, and that the airlines aren’t leaking.
- A real easy way to check your brakes regardless of what operating system you have, is to get in and make sure the vehicle is on a level surface. Put the vehicle in gear and let it roll forward up to 5 mph and then apply your brake pedal to see if it actually stops the vehicle and doesn’t make the vehicle shift to one side or the other when applying the brakes.
If you ever run into anything that concerns you regarding brakes and you are just tired of trying to chase down an answer, please feel free to contact us any time and we will either help you find the answer or lead you down the right road.
Stay safe and keep the rubber side down.