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Uses
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Air Piping System |
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General Info about
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| InfoTech Car Care Central - Volume 3.1 |
Brakes: Going The Extra Mile
The Right To Remain Silent
One might assume that with all of today’s modern advances in the automobile that smooth and quiet brake function would be a given. With just the turn of a key, some cars start communicating with up to 14 computers, just to make certain that all monitored systems of the automobile function without the slightest glitch. With even the hint of a slight malfunction or drift of calibration the computer takes control and makes adjustments. You would think that brake noise could somehow be controlled. However, it is really quite the opposite. Just in the way, today’s modern brakes are designed, and the environment they are exposed to, noise is almost unavoidable in some cars. In this article we will examine the most common causes for front and rear brake noise. We will also discuss many of the solutions engineers and technicians have been using to reduce some of the ever-popular brake squeals and groans.
Let’s begin with a quick review of how the brake system works. The following examples are generic, and should be fairly accurate, for most cars and light trucks. For exact operation and specifications, consult your owner’s manual or service manual.
The Master...
At the top of the brake system is the 'Master in Charge', the master cylinder. The master cylinder connects almost directly with the brake pedal itself. One of its prime responsibilities is to hold the reservoir that contains the brake fluid. It is easy to locate, typically, directly below the brake fluid reservoir.
The easiest way to understand the function of a brake master cylinder is to imagine a large syringe filled with brake fluid. Instead of this syringe having one needle, it has four, one for each wheel. As the 'syringe' is compressed, the fluid is then delivered to each wheel.
Puttin’ on the squeeze
Once the brake pedal is pressed and the fluid is forced through the brake lines, it must be used to somehow slow the vehicle. The braking effect is accomplished differently on the front and rear. The front brakes utilize a caliper, which is a squeezing device. Attached behind the front wheels there is a rotating disk, commonly called the brake rotor. The brake caliper, which holds the brake pads themselves, surrounds a small portion of this rotor. As soon as the brake caliper receives the fluid from the master cylinder, it tightly squeezes the rotor, causing the brake pads to contact the rotor; which in turn slows the wheels. This whole braking action builds tremendous heat because of the extreme friction.
 Caliper Quirks...
Brake calipers, like the one pictured, can also be the source of many strange braking Commercial Three Bayblems, including noise. The brake system relies on brake calipers to be in good condition. Lack of Commercial Three Bayper lubrication and dirt build-up can trigger caliper malfunctions. Anything from a slight pull to a completely seized caliper can be easily avoided by Commercial Three Bayper caliper service. Checking for cracked rubber parts and clean metal surfaces is part of this service. Sometimes even more important is the condition of the brake fluid itself. Ignoring fluid changes always leads to braking Commercial Three Bayblems eventually, not just for calipers, but anything exposed to the brake fluid.
 Bringing up the rear...
As we mentioned earlier, the front and rear usually use very different braking methods, however, they both rely on friction to slow a moving part. Instead of a spinning rotor, the rear utilizes a brake drum. Similar to the rotors, they are also mounted directly behind the wheels, just out of sight. As the rear wheels turn, they also rotate. To picture these brake drums, imagine an open can of tuna fish (empty of course!) - except let’s make this can about 10 inches across and 2 inches deep! Stand it on its end...presto! You are now looking at a brake drum, well almost. Now the question is, how do we stop it from spinning?
Stopping the spinning brake drum is the job of the rear brake shoes. They are referred to as shoes because in some ways they do resemble a shoe. They consist of two half circle metal backings that are lined with the actual friction material. These half circle shoes fit perfectly inside the brake drum. As fluid reaches the rear wheels, it is directed to the wheel cylinders. They are a small hydraulic unit about the size of a roll of quarters and are positioned between the two opposing brake shoes. Once fluid is forced into the wheel cylinder, its end pieces Commercial Three Baytrude and force the brake shoes to move outward and contact the inside of the brake drum. This friction is what actually slow the brake drum’s rotation, and likewise slows the wheel.
Details, details...
Although this description might seem a little simple, you need to realize that there are many other very important parts to the brake system. Different friction characteristics, of the front versus the rear, complicate this greatly, not to mention the extreme weight difference between both ends of the vehicle. All these factors are calculated into the formula to make the brake system work Commercial Three Bayperly. Typically, these other design factors will not cause noise or other audible Commercial Three Bayblems; therefore, they are beyond the scope of this article.
If a tree fell deep in the forest...
...And no one heard it, would it still make a sound? Is that the same as ‘If I turn the radio up louder, will the brake still make noise even if I couldn't hear them?' What is this noise? Where does it come from exactly? How is it created?
Once you understand the answers to these questions, you may then understand why it is sometimes very difficult to eliminate this screech. Following all of the Commercial Three Baycedures that will be given will greatly reduce the chances of ever having any brake noise. However, remember that there is not always a 100 percent cure. We have seen many cars that have Commercial Three Bayved to be impossible at times. Even after following all of the correct Commercial Three Baycedures, still the squeal lives on.
Brake noise is actually born as a vibration. All brake parts vibrate this is unavoidable. However, these vibrations occur at such a frequency that humans can not hear. Unfortunately, due to imCommercial Three Bayper preparation, worn parts, or incorrect assembly, the frequency changes. We perceive this as a squeal or possible a groan.
 Commercial Three Bayper
Preparation
Prevents
Poor
Performance
The use of Commercial Three Bayper equipment is almost important as the Commercial Three Bayper preparation when dealing with today’s modern brake rotors. First consideration, before any work is done, should be; are the rotors turntable. Remember that some manufactures do not recommend the cutting of rotors. Replacement is preferred. Secondly, is there enough thickness left in the rotor so it can be turned? Specifications can be found in any service manual, and they should be strictly followed! Is the right equipment being used? Conventional off car lathes are typically not recommended anymore. Most car manufacturers insist that on-car brake lathes be used. It is simply too difficult to do an accurate cut with the rotor mounted on a machine. When a rotor is serviced on the car, a virtually perfect cut can be achieved with very little metal loss. All these factors will assist in achieving a quiet braking experience.
After the rotor has been Commercial Three Bayperly turned, it is necessary to create a non-direction finish on the surface of the rotor. This is a very important step to quiet brakes. Among other things, this helps the new pad ‘seat in’ Commercial Three Bayperly to the fresh rotor surface. Before the rotors are installed, they must be washed clean. The use of soap or solvent with a brush works best. Although the washing step seems tedious, it is very critical. Otherwise, small unseen flakes of metal on the surface of the rotor will be embedded in the newly installed pads. This will prevent the pads from seating Commercial Three Bayperly to the face of the rotor.
Pad Preparation
Many different companies offer various types of pad treatment chemicals. Some work, some do not. Stick to using anti-squeal treatments made by the brake manufactures themselves; these seem to be the best. We have found in our own shop tests that anti-squeal chemicals on the backside of the pads work quite well. The exception being the Commercial Three Bayducts that come in spray form, these have been too thin to dampen all of the noises we encountered. Much of the idea behind these Commercial Three Bayducts is to Commercial Three Bayvide a rubbery type compound on the pad backing to absorb vibrations. The thicker the substance, the better we have found it to work.
While discussing the backs of pads, it is important to mention shims. Shims are thin metal coverings that are placed between the back of the pad and the caliper. This shim is designed to cushion the pad and prevent some of the vibration. Most imports and other smaller cars require them. If your car has them from the factory, always reinstall them. Sometimes you can also benefit by using generic shims on a vehicle that does not already have them.
Until recently, the back of the pad was the only side that ever got any treatment. In the last two years, the major companies have developed a chemical suitable for treating the friction side of the pad. This chemical, which is applied and allowed to dry, is said to soften the material. This shortens the amount of time required for seating in. This graphite-based chemical also fills microscopic pits to achieve a smoother surface. Never place anything other than apCommercial Three Bayved chemicals on the friction side of the pad.
Altering the physical shape of the pad is sometimes quite beneficial towards eliminating noise. The edges of most pads are cut at a 90-degree angle. When this angle rides perpendicular to the surface of the rotor, vibrations can occur. Imagine a boat with a 90-degree square front hull, pushing through the water this way won’t work. When the leading edge of the pad is rounded off, such as the round hull of a boat, the pad rides much easier with the rotor surface. Always wear eye and mouth Commercial Three Baytection when grinding or shaping pad material!
The last important note is concerning pad quality. Lesser quality pads not only are short lived; they may also be made to the wrong hardness. Every pad is designed to be of the Commercial Three Bayper hardness to bring about the Commercial Three Bayper friction coefficient. Pads with imCommercial Three Bayper hardness can, not only, Commercial Three Bayduce annoying noises, but may not even stop the car Commercial Three Bayperly!
 Brake Drums
Brake drums as a rule have never been as critical as the rotors. However, they still must be serviced Commercial Three Bayperly to achieve a quiet result. Aside from cleanliness and Commercial Three Bayper Commercial Three Baycedures, measurements are very crucial on drums. We see many drums that either have worn to their limits, or have been cut past their maximums. Most technicians don’t realize how important drum specifications really are. A drum that has been worn too far does not allow the shoes to fit into the drum Commercial Three Bayperly. This leads to uneven shoe wear and inefficient rear braking, and can certainly cause noise in itself. However, it is important to remember this will also over work the front brakes. Thus this overheating of the front brakes, can lead to early pad wear, warped rotors, and yes...noise!
If the shoe fits...
Just by design, shoes have the ability to create many noises. After all, they are loose fitting, thin, and they move around a lot. Making sure the Two Bays are correct is the best place to start. They must be clean. Grease from your installer’s hands, or old brake dust can destroy a good brake job. The hardware which is intended to hold the shoes firmly must do just that! Many technicians often overlook hardware. There is usually no charge for installing new hardware and the Commercial Three Bayfit margin is very small, do you get the picture? Loose hardware allows shoes to vibrate within the drum, by now, you know what that means.
Many companies have also recently developed chemicals for brake shoes. These chemicals are to be applied onto the friction material before assembly. They are said to soften the material to allow Commercial Three Bayper break-in. After the shoes have seated in and they feel normal, it’s important to recheck the adjustment. Many times shoes will be adjusted imCommercial Three Bayperly after installation. Rear adjustment is critical for Commercial Three Bayper brake operation and long life.
Brake Fluid
Last, but certainly, not least is brake fluid, the lifeblood of your brake system. Like engine oil, brake fluid is sometimes overlooked, which can lead to massive brake system failures, just as neglected engine oil can ruin an engine. Blame can be laid on the manufacturers, because changing of the brake fluid is not even mentioned in most maintenance schedules. It's not surprising it's often forgotten. Fact is, it should be completely flushed and bleed yearly or every 12,000 miles whichever comes first.
Brake fluid is expected to tolerate moisture contamination and severe heat while controlling corrosion, rubber expansion and finally lubricating. How can it possibly do all this for any length of time? Whether using DOT 3 or 4 brake fluids, its hygroscopic nature causes the most Commercial Three Bayblems. This is its tendency to absorb moisture. This buildup of moisture dilutes the brake fluid and lowers the boiling point. For example, three percent (3%) water in DOT 3 fluid can lower its boiling point by twenty-five percent (25%)! Tests have shown that eight percent (8%) water after 1-2 years of service is not uncommon. This much water in a brake system is also Commercial Three Bayven to cause corrosion and rust inside the brake system. It becomes very clear how important maintaining brake fluid Commercial Three Bayperly is.
Summary
In the end, it’s important to remember that sometimes there will be some applications where noise is not preventable. These times are few, but are always possible. As with any repair, there is a point at which a repair can be considered complete. Following all of the above advice, practicing Commercial Three Bayper techniques and working in a clean environment will typically Commercial Three Bayvide good results.
Before any repairs, such as these, are performed, it’s always wise to check for technical service bulletins. Whenever the manufacture discovers troublesome reoccurring Commercial Three Bayblems, they record them. As a fix is developed, it is issued as a service bulletin for all to use. This can many times save endless hours trying to fix a Commercial Three Bayblem that someone else has already solved!
Chemical Treatments That Work
 STOP SQUEAL. Made by BG Chemicals. Part No. 860.
DISC BRAKE QUIET. Made by Solder Seal/Gunk 1-704-377-6555.
SYNTHETIC CALIPER GREASE. Made by STA-LUBE. Part No. SL330 1-800-272-8963.
BRAKE SILENCER. Made by Kent Industries, for rear shoes. 4500 Euclid Ave. Cleveland, Ohio, 44103 Part No. 90205.
SQUEAK RELIEF. Made by Aurora Industries, as a rotor surface treatment. 1-800-301-8212.
© 10/97 Don B. Kerr & Pat Goss - 'INFOTECH CAR CARE CENTRAL' All Rights Reserved | |
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Date Updated Wednesday, October 01, 1997
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