Fix Your Brakes

Repair brakes right away

If your 4×4 is not stopping at it should take a look at your brake right away or have it looked by someone. Waiting until a problem gets serious is playing with your family’s life.

Brake repairs – critical? Of course! Your brakes keep your family safe. Brake repairs and parts for imports – expensive? You bet! Brake rotors for import cars, unlike domestics, are built with minimal thicknesses to save weight – meaning they can’t be “turned”; they must be replaced.

Brake rotors for imports are also more sensitive to warping from heat, and overheated brakes are the second most common cause of failure (first is wear-and-tear).

What do brakes do?

Brakes are designed to slow down your vehicle but probably not by the means that you think. The common misconception is that brakes squeeze against a drum or disc, and the pressure of the squeezing action is what slows you down. This in fact is only part of the reason you slow down. Brakes are essentially a mechanism to change energy types. When you’re travelling at speed, your vehicle has kinetic energy. When you apply the brakes, the pads or shoes that press against the brake drum or rotor convert that energy into thermal energy via friction. The cooling of the brakes dissipates the heat and the vehicle slows down. This is all to do with The First Law of Thermodynamics, sometimes known as the law of conservation of energy. This states that energy cannot be created nor destroyed, it can only be converted from one form to another. In the case of brakes, it is converted from kinetic energy to thermal energy.
Angular force. Because of the configuration of the brake pads and rotor in a disc brake, the location of the point of contact where the friction is generated also provides a mechanical moment to resist the turning motion of the rotor.

In order to understand the how and why of brake repair, you first have to get to know the two types of brakes: drum brakes and disc brakes. In essence, a drum braking system works by pressing brake shoes outward against the inside of a round metal drum. Disc brakes, on the other hand, use brake pads to squeeze a spinning metal disc in order to slow (and stop) your car. Drum brakes are becoming less common and today generally only show up on the rear half of some domestic vehicles, including economy cars, mini-vans, and light trucks. They operate on the same principle as the more prominent disc brakes — utilizing friction.

Drum Brake System

drum brakeThe concept here is simple. Two semicircular brake shoes sit inside a spinning drum which is attached to the wheel. When you apply the brakes, the shoes are expanded outwards to press against the inside of the drum. This creates friction, which creates heat, which transfers kinetic energy, which slows you down.  The actuator in this case is the elliptical object. As that is twisted, it forces against the brake shoes and in turn forces them to expand outwards. The return spring is what pulls the shoes back away from the surface of the brake drum when the brakes are released.

Drum brake systems work by using hydraulic pressure to press a pad against the brake drum to slow the vehicle. When the brake pedal is pressed, it acts upon the piston in the master cylinder which sends pressure via the brake lines to the wheel cylinders inside the brake drum. The shoe-to-drum friction stops the wheel from turning.  

A drum brake assembly is used to bring the rear wheels of most vehicles to a stop. Fluid pressure from the master cylinder causes the wheel cylinder to push the brake shoes against the brake drums which are attached to the vehicle’s rear wheels. The friction between the stationary shoes and the revolving drums causes the drums to slow and stop the rear wheels.

The “single leading edge” refers to the number of parts of the brake shoe which actually contact the spinning drum. Because the brake shoe pivots at one end, simple geometry means that the entire brake pad cannot contact the brake drum. The leading edge is the term given to the part of the brake pad which does contact the drum, and in the case of a single leading edge system, it’s the part of the pad closest to the actuator. The diagram below shows what happens as the brakes are applied. The shoes are pressed outwards and the part of the brake pad which first contacts the drum is the leading edge. The action of the drum spinning actually helps to draw the brake pad outwards because of friction, which causes the brakes to “bite”. The trailing edge of the brake shoe makes virtually no contact with the drum at all. This simple geometry explains why it’s really difficult to stop a vehicle rolling backwards if it’s equipped only with single leading edge drum brakes. As the drum spins backwards, the leading edge of the shoe becomes the trailing edge and thus doesn’t bite.

The drawbacks of the single leading edge style of drum brake can be eliminated by adding a second return spring and turning the pivot point into a second actuator. Now when the brakes are applied, the shoes are pressed outwards at two points. So each brake pad now has one leading and one trailing edge. Because there are two brake shoes, there are two brake pads, which means there are two leading edges. Hence the name double leading edge.

The major advantage of drum brakes is that an emergency brake mechanism can easily be incorporated into it.

Worn drums and shoes, however, can cause unreliable stopping, excessive pedal effort, or brake pedal pulsation.

Brake Drum

The brake drum is a heavy flat-topped cylinder, which is usually located between the wheel rim and the drive wheel. When the brakes are applied, the friction material of the brake shoes is forced into contact with the brake drum to slow the rotation of the wheels.

 

Wheel Cylinder

wheel cylinder of drum brakeThe wheel cylinder is a cylinder that contains pistons which use hydraulic force from the master cylinder to push the brake pads against the brake drum.

The wheel cylinder is a critical element in the drum brake assembly. It contains fluid-activated pistons that push the shoes against the drums to slow the wheels. The wheel cylinder is also the source of many brake problems. If brake fluid leaks from the wheel cylinder, the vehicle could experience unreliable stopping, damage to new brake shoes, or partial brake system failure. A sticking wheel cylinder may cause brake drag, excessive pedal effort, and reduced braking efficiency.

Brake Shoe

The brake shoe holds the brake lining and is used to force the lining against the drum when the brake is depressed.

 

Master Cylinder

master cylinderThe master cylinder moves brake fluid under pressure to rest of the braking system.

The diagram on the left is a simplified representation of a dual-circuit master brake cylinder. When you step on the brake, it is connected to the main plunger (on the right side of this image). As this is pushed into the master cylinder it acts on the components inside. The rear plunger (in blue) is the first one to start moving. As it moves forward, brake fluid from the reservoir is sucked in through the fluid intake and return port. At the same time, fluid is sucked in through the equalization port. As the second circuit rear seal passes the intake and return port (about 1.5mm after the plunger starts moving), it creates a fixed volume of fluid between the rear and front plungers. The more you step on the brake pedal, the more this fluid is now forced out into the second brake circuit to apply those brakes. At the same time, the pressure building up in this area overcomes the strength of the first circuit return spring and the front plunger (red) begins to move too. As with the rear plunger, it too sucks fluid from the reservoir until the first circuit rear seal passes the fluid intake and return port (again about 1.5mm), trapping fluid between it and the front of the master cylinder. This fluid is then forced out into the first brake circuit, applying those brakes. When you take your foot off the brakes, the return springs push the plungers back into their neutral position. Fluid returns to the brake fluid reservoir and the system goes back to an unpressurised state.

Brake Pedal The brake pedal works as a lever to apply pressure against the master cylinder.

 

Disk Brake System

disk-brake-assemblyDisc brakes are the preeminent choice for all manufacturers; even those employing drum brakes in the back will invariably have disc brakes in the front. In short, this type of brake system is superior in terms of design and essentially operates like a drum brake turned inside out. This type of brake system is most likely what you have on your current vehicle.

Sportier vehicles with higher speeds need better brakes to slow them down, so you’ll likely see disc brakes on the rear of those too. Disc brakes are again a two-part system. Instead of the drum, you have a disc or rotor, and instead of the brake shoes, you now have brake caliper assemblies. The caliper assemblies contain one or more hydraulic pistons which push against the back of the brake pads, clamping them together around the spinning rotor. The harder they clamp together, the more friction is generated, which means more heat, which means more kinetic energy transfer, which slows you down. You get the idea by now.

Disk brake systems work by using hydraulic pressure to press a pad against the rotor to slow the vehicle. When the brake pedal is pressed, it acts upon the piston in the master cylinder which sends pressure via the brake lines to the caliper. The pad-to-rotor friction stops the wheel from turning.

Because a disc brake assembly can absorb more heat than a drum brake assembly, most cars use disc brakes for their front brake systems. When the brake pedal is pushed, brake fluid from the master cylinder compresses the brake pads against the rotors attached to the vehicle’s front wheels. The friction between the stationary pads and the revolving rotors causes the rotors and wheel to slow and stop.

Rotor or Disk brake

The rotor is a circular plate that is gripped by the brake pads in order to slow the vehicle.

 

Brake Pad

The brake pad is friction material that is pressed against the rotor to stop the wheel from turning.

Caliper

The caliper holds the brake pads. It straddles the rotor and uses hydraulic pressure from the brake lines, along with internal pistons, to force the brake pads against the rotor.

 

Brake Pedal

brake pedalThe brake pedal is directly attached to the master cylinder and acts as a lever to apply pressure against the master cylinder. Pedal pulsation, excessive pedal travel, a “soft” or “hard” pedal can be indicators of serious problems, including a leak in the hydraulic system, low fluid levels, or unevenly worn shoes or pads.

 

Master Cylinder

master cylinder of disk brakeThe master cylinder moves brake fluid under pressure to the rest of the braking system.

The master cylinder acts as a holding tank for brake fluid until it is needed. When the brake pedal is depressed, the master cylinder forces fluid to each of the vehicle’s wheels. Wear on the master cylinder’s moving parts may allow brake fluid to leak, causing unreliable stopping or possible system failure.

 

 

 

Save money on brake repairs and parts with these tips:

Use Your Eyes & Ears to Inspect Your Brakes

Visually inspect your brakes’ condition at least every six months. Here are some things to look for:

Hear No Evil

For example, a grinding noise coming from any of the wheels could be a sign of wearing pads or rotors. Squeaking or squealing brakes, however, don’t necessarily mean your brakes aren’t in optimal working order; some systems are simply noisier than others due to materials used and design (if, however, there’s a major change in the noise you usually hear, that could be cause for concern).

See No Evil

Likewise, if you notice an unusual accumulation of dark dust on your hubcaps/rims, especially on the rear wheels, it may be a sign that your brakes and/or rotors need attention. Most vehicles have a front brake bias, meaning that the front brakes play a larger part than the back brakes, so it’s common to see some dust on the front. If, however, you see brake dust accumulating on the rear wheels, or an unusual amount of it on the front wheels, you’re wise to take your vehicle in for a check-up.

Inspect each item individually for the following:

Brake Rotors (disc brakes) should be inspected all the way around the surface and on both sides for any concentric scoring (grooves) or obvious defects. If defects are found, replace your rotors immediately. Any rotor discoloration may be a sign of overheating and an inspection by a brake repair professional is needed.

Brake Pads will normally match rotor scoring but should also be inspected for uneven wear, breakage or cracking on the friction surface. Again, if defects are found, replace the pads immediately. Many cars also have brake pad sensors to warn of pad wear. If your car uses sensors, replace these at the same time as your pads.

Brake Drums (if equipped) should also be inspected on a regular basis. Check for the same types of flaws as noted above. The drums should not have excessive grooves or have a deep “trough” dug into them where the shoes ride.

Brake Shoes (if equipped) should be worn evenly and have no rivets protruding to the friction surface.

Additional Troubleshooting: When inspecting brakes, check calipers, wheel cylinders, hoses and fittings for any hydraulic fluid leakage.

Inspect the master cylinder, reservoir and proportioning valve assemblies as well. Replace or rebuild as required.

A “spongy” brake pedal or one that’s gotten lower underfoot also needs looking into. It could be caused by sticking calipers, worn pads, low fluid or hydraulic system problems.

If you can’t “pump them up”, then you definitely have hydraulic problems that need work. If you always have to pump them up, at the very least your hydraulic fluid needs replacement.

To check brakes by sound, know how your brakes should sound and listen for out-of-the-ordinary noises.

Most cars have a slight brushing sound from the pads lightly touching the rotors. This is perfectly normal. Sounds to beware of include:

Squeaking may be caused by dust or dirt on the brakes, loose pads vibrating when applied or worn pads.

Rhythmic noise might mean you have a warped rotor. Instead of a solid squeaking noise, it pulsates. In extreme cases, the brake pedal will also pulsate underfoot.

Constant brake noise is never a good sound and any grinding noise spells real trouble!

Most importantly: As soon as any problem is noticed, get it repaired immediately. Delaying brake repairs is extremely dangerous.

Overstressed rotors and drums can break. Brakes may be too worn or damaged to stop your car in an emergency.

Even if you manage to avoid physical harm, the longer you delay fixing brake problems, the more you increase the cost of doing so.

Badly worn, warped or overheated rotors can damage wheel bearings and the complete wheel hub assembly. These parts often cost as much or more than the brakes themselves.

Even if you like doing your own work, every few years your brakes should be examined by a professional. Checking brakes for “run-out”, warping, wheel bearing play, proper proportioning balance, among others, are normally more involved than can be accomplished in your garage. This inspection can also uncover underlying problems that could eventually become costly or dangerous.

Feel No Evil

Then there’s the feel of your vehicle as you drive it. Over time, if it feels as though you have to put more pressure on your brake pedal to produce stopping (also known as “fade”), or your brake pedal nearly touches the floor of your car when you attempt to stop, it may be a sign that there’s an issue with the pads and rotors, or you may have a problem with your brake fluid.

A word about brake fluid: it must endure high pressure and extreme temperatures, and can therefore break down or leak over time. It should be replaced during every major brake service, but this could be required more often in older vehicles or those with higher mileage. When speaking with your service advisor, you’ll hear the terms “brake flush,” which refers to draining the system of its old fluid and replacing it with new stuff, and “bleed,” which is the procedure to remove any air bubbles or unequal pressure from your brake system.

Preparing to Be Serviced

When it comes to price, you’ll find it varies. A full set of pads and rotors can cost anywhere from $250 to $800, depending on the make and model of the car. A brake flush service (which may include a bleed) should typically run you $50 to $120.

If you’re using a dealership for your service, it makes sense to call at least two ahead of time to compare prices. While they’ll tell you your system will need to be checked to determine exactly what needs to be repaired, the quotes you receive will still be helpful in identifying the more cost effective location.

If you’re using a non-dealer facility (such as an independent or chain repair shop), you’ll want to be armed with some basic vernacular to illustrate your knowledge and avoid being taken advantage of. Because rotors last longer than pads, for example, you might want to suggest that the rotors simply be “spun” as opposed to replaced entirely (just know that some dealers and shops only provide full replacement service, so spinning your rotors may not be an option).

Additionally, if you ask, any shop should be able to tell you what “percentage” of life is left in each of your components. Not only is this beneficial in helping you determine whether or not you can postpone your brake service a while, but it also illustrates that you’re unwilling to pay for unnecessary work.

Do It Yourself

Replacing brake pads is generally a fairly straightforward task, so you can certainly save some money by completing this service yourself if you have the appropriate mechanical experience and supplies. If you need to go out and purchase a jack, jack stands, caliper tool, or model-specific service guide, you probably won’t save enough to make it worthwhile. But if you happen to own all of these already and have worked on cars before, you might consider the do-it-yourself approach.

Important Things to Remember

Heed these tips and you’re on your way to ensuring your brakes won’t fail:

Tip #1: Keep the hydraulic reservoir at the proper level with the fluid type recommended by the car manufacturer. Never substitute or mix types of fluid. Remember also that hydraulic fluid absorbs water. Never use old hydraulic fluid – always use a fresh container.

Tip #2: Keep brakes clean by washing them off at the same time as your car. This keeps squeaky dust and dirt off the pads and makes brakes easier to inspect and work on.

Tip #3: Never spray, touch or drip any oil or lubricants on the brake friction surfaces. If this occurs, spray immediately with brake cleaner to remove completely.

Tip #4: There are no shortcuts or quick fixes to brake problems. They either function properly or they don’t. Know your brake system – how it should work, feel and sound – before it acts up so you’ll know when something’s wrong.

Tip #5: Most imports don’t have serviceable rotors. They must be replaced at the same time as the pads. The rotors cannot be “turned” to remove imperfections. There isn’t sufficient metal thickness to safely accomplish this.

Tip #6: Keep a repair log with receipts when any service is performed on your car. It helps when you need to check if your warranty is still in effect. More importantly, it’s a great gauge of performance and an indicator of other problems.

Tip #7: Whenever the pads are replaced, the hydraulic system must be bled to remove any air bubbles. Most specialists recommend changing the fluid with every pad replacement. If you’re unsure of the proper technique for bleeding the hydraulic system, don’t perform the job yourself. Seek help from a professional. ABS equipped cars should be bled only by professionals.

Tip #8: Most noises are usually related to your pads. However, whenever replacing pads, you should also replace the sensors and seriously consider replacing the rotors at the same time.

Tip #9: After installing new pads, remember to “set” them properly. This conditions them for maximum performance and prevents premature failure. Instructions for setting pads is usually provided in the package with your new pads.

Brake Parts Shopping List

When shopping for parts, remember two important things:

1. OEM/OES (original equipment manufactured/supplied) or equivalent pads and rotors are not always cheap. You do, however, get what you pay for. OE parts will give you the most trouble-free driving and peace of mind. And . . . isn’t that what’s most important?

2. Before requesting any brake parts for your import car, make sure you have the year, exact model designation, engine size and type, brake configuration, type of rotors (solid or vented), vehicle ID number (VIN) and production date. For Volvos, you’ll also need rotor diameter, caliper manufacturer and mount and shape of the pads.

Here is a list of parts you should consider when working on brake systems:

– Front Brake Rotors (Brake Discs) –
– Front Brake Pads –
– Rear Brake Rotors (Brake Discs) or Rear Brake Drums –
– Rear Brake Pads or Brake Shoes –
– Brake Sensors (front and/or rear, as applicable)
– Brake Calipers or Caliper Rebuild Kits –
– Wheel Cylinders –
– Hydraulic Hoses –
– Hose/Tube Fittings –
– Brake Master Cylinder –
– Power Booster –
– Reservoir & Grommets –
– Brake Proportioning Valve Assembly –
– Hydraulic & Brake Fluid –
– Brake Cleaner –
– Anti-Squeal Compound –

 

Don’t Forget:

Repair articles are added regularly.
Come back often to check for new maintenance topics.

These repair tips are designed only as a starting point.
Please seek the assistance of a professional mechanic
for all repair problems beyond your capabilities.

 

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