Category Archives: Brakes

Blogs concerning Brakes

Stop, Go, Swerve: What to do if there is an animal in the roadway

While my grandmother has been known to make road kill stew, this isn’t a delicacy that most enjoy. Being prepared to encounter animals and knowing what to do when these encounters occur is a better way to use the road efficiently. Reacting quickly and correctly will help to protect the lives of all humans and animals involved in an incident.

With roadways becoming more crowded and suburban developments encroaching on wild habitats, animal-related accidents have been on the rise in recent years. According to State Farm, 1.2 million animal-related accident claims were made in 2008, representing an increase of 15 percent since 2003. Failure on the part of human drivers to respond correctly to these situations makes many of these accidents worse than they need to be.

When we see an animal—or other obstacle—in the road, our typical instinctive response is to swerve to avoid the obstacle. This would only make sense in a situation where one was driving slowly on an empty road. Under any other conditions, swerving can create more problems than it solves: if traveling quickly, you could enter a skid or flip your car; you could send your car hurtling off the road and into another obstacle; or you could put your car in the way of oncoming traffic.

According to experts, the best response is to remain in your lane while attempting to slow down as quickly as possible. If you have room to do so, move toward the right side, or outer edge, of the road. When you accidentally step too close to a hazard, your first instinct is likely to jump back; an animal, however, will instinctively move faster along its chosen path, i.e. forward across the road. Moving slightly in the direction that the animal was coming from and slowing down will, ideally, give the animal time and space to escape safely.

Next, be aware of your surroundings. If you’re driving through a rural area or have noticed a number of deer or moose crossing signs, be particularly alert; scan the edges of the road to see if you can spot any animals lurking on the shoulders. If you have passengers, ask them to scan the roadsides for animals. At night, animals’ eyes will glow (the exception being moose, whose eyes do not reflect light.)

If you do, slow down and be particularly vigilant. Never speed, especially at night; remember that you should always be able to stop within the area illuminated by your headlights. Experts recommend traveling no more than 55mph in high-density wildlife areas. This speed should be reduced in inclement weather. Many animals, including deer and moose, are most active at dusk and dawn, when our visibility is often limited. Be particularly alert during these hours. You should use your high beams when not surrounded by other drivers and, if possible, move the car as close to the center of the road as possible.

If you do end up in a collision with a moose or deer, duck down into your car; large animals like these can come through the windshield or crush the car roof. Should you end up in a collision with an animal, first check to make sure that your passengers are okay. If the injured animal is still alive, do not approach it, as, scared and in pain, it could still be dangerous. Only attempt to move the animal out of the road if you are certain that it is dead. Use flares or emergency lights to alert others on the road to your predicament and call the police.

To read more on a broad range of subjects from “How To Change A Tire” to “How To Jumpstart Your Car”, visit DefensiveDriving.com’s Safe Driver Resources website!

Check out these sites for more information about defensive driving and business driver safety.

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Safe Driving in Snow and Ice!

Few things are as beautiful as the first snowfall—suddenly the drab, leafless trees are transformed by a coating of fresh powder; a mundane street becomes a wondrous new world. Unfortunately, driving conditions are also transformed by winter weather, making even the most familiar routes extremely treacherous. It’s no surprise that snow and ice are both among the top twenty-five causes of car accidents in the US. However, with experience, preparation, and patience, you can feel relatively safe in most winter conditions.

Having grown up in a northern state, I remember that my parents insisted I learn to drive twice: first, in the summer, when the roads were clear; then again, in the winter, when the first snow fell. The car felt completely different in the winter, and I had to recalibrate my steering, braking, and sense of speed, as well as my sense of space, since the roads were significantly narrowed by snow banks. My first piece of advice, then, for those who may be acclimating to a new winter driving climate is: practice. Don’t plan to travel much during your first snowstorm. Instead, have a friend take you to a parking lot or similar open stretch of pavement where you can practice snow driving in a safe environment. Wait until you’ve a got a bit more of a feel for how your car will handle in snow before heading out on the frozen road.

As the fall gets colder, start making preparations for the winter season. First, get your car serviced before the first snow storm. Check the lights, brakes, heating and defrost systems, antifreeze level, and other basics. This is a good time to repair minor chips in the windshield as well, as these can expand in winter weather. It may be a good idea to coat your windshield with a water repellant; this will help with visibility when driving in rain and snow.

If you live in an area that experiences severe winter conditions, you may want to invest in snow tires or chains. Snow tires are a special tire made of a slightly softer rubber, making them more flexible in winter, and with smaller tread grooves. Some areas that experience severe weather may actually require that snow tires be fitted in winter. Snow chains are just what they sound like: chains that fit over one’s wheels to improve traction on very snowy or icy surfaces. These are used in more extreme snow conditions, as snow chains can’t be used on dry roads and limit one’s speed to no more than 30 mph. In areas with heavy snow, you may also want to install heavy-duty wiper blades and/or mud guards and flaps, which will help to keep salt from the roads from corroding your car. Finally, cold weather can decrease your tire pressure, so make sure you keep checking your tires as the temperature drops.

In addition to making sure one’s car is in good shape, it’s also a good idea to have the necessary supplies on hand. Before the start of winter, make sure your car contains a spare tire, shovel, scraper, jumper cables, and salt, cat litter, or gravel (for creating traction on particularly slippery roads.) Creating an emergency kit for your car, which will contain first aid supplies, matches, flares, and other similar necessities, may also be a good idea. Make sure to store these items in a water proof container.

Once you’re ready to head out on the road, proceed with caution! Snow and ice can be deceptive. First of all, you may not notice ice on the road, particular if it is slick “black ice.” The sun’s glare can also give ice the appearance of water on the road, so drive slowly when approaching what appears to be a wet surface in cold weather. Bridges, infrequently used streets, and shaded areas also tend to freeze first and stay frozen longer, so approach these areas with extra caution.

For this reason, make sure you are always looking ahead in winter weather, so as to be aware of hazards that may be approaching. This also means keeping a good distance between you and the car ahead of you. Following in the tracks of cars ahead is a good way to access slightly “drier” bits of pavement during bad conditions; however, remember that it’s much more difficult to stop quickly on snow and ice, so you need to give yourself and other cars plenty of space. This includes snow plows and sand trucks. Remember that these vehicles are your friends, even if they are slow! Don’t try to pass a plow, as plow trucks often have poor visibility; besides, the road behind a plow is most likely much safer than the road in front of it! Give yourself extra time to reach your destination so that you aren’t tempted to rush in winter weather.

As in most treacherous driving conditions, avoid sudden movements. Try to steer smoothly and brake gently, especially before you enter a curve or turn. Braking suddenly or over-steering can cause a skid. Make sure you review tips on dealing with spins and skids before heading out, as well.  Avoid using overdrive or cruise control, but do use lower gears if climbing hills in the snow. Turn on your low beams to increase your visibility; if your wipers are on, your lights should probably be on too. In real blizzard weather, you may want to use your emergency flashers as well.

Above all, drive slowly! Conditions can change very quickly in the winter, especially with the onset of a bad storm. Be aware of what is happening outside your car and how your car reacts. Then, adjust accordingly. Err on the side of caution. Being late is annoying, but it isn’t life threatening.

Getting stuck in the snow can be a problem, especially if you make the mistake of backing into a snow bank (not that I’ve ever done that!). Since we’re now heading into warmer months, I’ll leave you in suspense for a while, as I’ll deal with being stuck in sand, mud, and snow in a later entry. Until then, try not to drive into a sand pit, swamp, or snow bank!

To read more on a broad range of subjects from “How To Change A Tire” to “How To Jumpstart Your Car”, visit DefensiveDriving.com’s Safe Driver Resources website!

Check out these sites for more information about defensive driving and business driver safety.

Common Brake Problems and Maintenance

Your brakes are easily one of the most important components of your car. Having well-maintained and effective brakes will go a long way towards keeping you safe on the road! Few things are more terrifying than jamming on the brakes in an emergency and finding they don’t work. Before reading further, it may be helpful to check out a previous entry on how brakes work. This will help you to understand some of the problems discussed here.

Should you experience brake failure, there are a few things you can do to slow down your car and minimize potential damage; check out these tips.  However, this situation is best avoided altogether!

First, practice good driving techniques to avoid putting excess wear on your brakes. Regularly braking hard—“slamming on the brakes”—puts a great deal of strain on your brakes. Driving in stop-and-go traffic also exacerbates brake wear; if possible, try to arrange your schedule so as to avoid the worst of rush hour. While driving, don’t “ride” the brake pedal or let your foot rest on it. Also, coasting to slow down before braking can help to save your brakes. Try to plan ahead; slow down if you see cars braking ahead. Look down the road a ways to spot other hazards, stop signs, and red lights that may be coming up in your path. Also avoid carrying excess weight in your car, as this will put extra strain on your brakes. Note that several of these strategies will also help you to save gas! Finally, there are different grades of brake shoes and brake pads. While the lower grade pads are cheaper initially, they will wear out faster and often don’t perform as well. Purchasing the higher grade pads and shoes will be more cost-effective in the long run and will reduce wear on the other components of your brake system as well.

Next, pay careful attention to the feel of your brakes when braking and the sound they make. Unusual noises and feelings can be symptoms of brake problems. Here are some of the most common problems and their causes:

Brake warning light comes on: This most likely indicates that there is a leak in the system. Don’t drive until you have had the system checked out, and any leaks have been repaired.

Brake pedal “rests” at a lower position: This is usually caused by drum brake adjusters not working properly. If the adjusters are rusty or they stick, they won’t advance properly. In addition to having the brakes readjusted, you will need to have the adjusters cleaned or replaced. This could also indicate that the brake pads or shoes need to be replaced or that there is a leak in the system.

“Spongy” brake pedal: If your brakes are “soft,” i.e. the pedal doesn’t offer as much resistance when you push it, then there is likely air in hydraulic system somewhere. Your mechanic will need to “bleed” brake lines, i.e. drain and replace the oil.

Need to push pedal too far in: This could be due to a variety of problem: worn brake pads or shoes, poorly adjusted drum brakes, or air in the lines. You can pump the pedal several times to compensate for this, but you will still need to get your brakes checked as soon as possible.

Pedal pulses or vibrates when you brake: This occurs when the rotors on the disc brakes, which should be flat, are worn unevenly. As a result, they don’t make contact evenly with the pads, which then causes vibrations. The rotors need to be resurfaced or, if the problem is severe, replaced.

A scraping noise: This occurs when there is metal to metal contact in the brakes, which means that you have worn entirely through the brake pads or shoes. A brake servicing is long overdue! Driving with shoes or pads this worn can seriously damage your brakes, forcing you to replace more expensive parts in your brakes.

A squealing noise: This can be caused by vibrations between the brake pads and rotor or caliper. This may be unavoidable on some older brakes which use semi-metallic compounds in the pads. Replacing the brake pads with newer ones can help. There are a few other strategies your mechanic can use to minimize this noise. However, this could also be a more serious problem, such as worn brake pads or a missing gasket, so do get your brakes checked soon.

A jerky, “slip-and-grab” feeling: It’s likely that brake oil or another substance has leaked onto to the brake mechanism. Contaminated pads will need to be replaced and, of course, the source of the contamination has to be identified and stopped.

Pedal sinks to the floor: This occurs when pressure isn’t being maintained in the hydraulic system. This is likely a leak or a worn-out master cylinder. Don’t drive in this situation! Instead, have your car towed and fixed immediately.

Brakes don’t release properly: There are several potential causes: the springs in the drum brake are not working properly; the floating caliper in the disc brakes isn’t adjusted correctly; the emergency brake cable or mechanism is broken; or the adjuster mechanism in drum brakes has extended too far.

Car swerves to one side when brakes are applied: This means that braking power isn’t evenly distributed between the front brakes. The car will “draw” to the side with the stronger brake, as the opposite wheel now has greater driving power. It’s likely that a leak, broken piston, stuck caliper, or other mechanical failure has occurred in one of the brakes. This can also be caused, however, by different brands of brake pads being used on the two front brakes, as different makes of pad and compounds have different braking properties.

Brakes are hard or difficult to use: Usually this means that the vacuum assist isn’t working properly, forcing you to put a lot more power into the system. The booster itself could be leaky or defective, or the check valve could be failing. You can test the check valve by running the engine for a few minutes (building vacuum) and then turning off car. If you don’t have power assist after a few minutes, the check valve is broken. To test the vacuum booster itself, turn off the engine. Pump the brake pedal a few times to “bleed” all remaining vacuum from the booster. Then, restart the engine and let it run for a couple of minutes. This should build vacuum in the booster again. Now, try your brakes. If there’s no power assist, this means that the vacuum booster is broken.

ABS Warning light comes on: This means that the computer has detected a problem in this system and turned it off. While this isn’t going to put you in immediate danger, it’s still better to have this system checked sooner rather than later.

Brakes lock: This is likely caused by a damaged brake pad or shoe. Have your car towed immediately.

In addition to listening for problems like these, you should also check your brake system periodically in order to stop problems before they happen. First, check the level of brake fluid in the reservoir often. If necessary, top up with fluid as needed; if the level of fluid seems to be sinking quickly, have your mechanic check for a leak.

Have your brake pads checked regularly and changed as needed. How often you will need to do this depends a lot on your driving habits and the car you drive. In general, brake shoes will need to be replaced after four rotations of brake pads.

Finally, take a moment from time to time to check that your brake lights are working.

 You should have a thorough “brake job” done either when the pads are worn down or if you notice any of the symptoms above. Your mechanic will carry out a variety of routine maintenance tasks, including replacing the front pads, resurfacing the rotors, replacing the shoes (if needed), resurfacing the brake drums, bleeding the brake lines, checking for leaks, and checking and adjusting the parking brake.

More comprehensive maintenance will also include new hardware for drums—springs in particular age with exposure to heat and should be replaced—and the of rebuilding wheel cylinders and calipers.

To read more on a broad range of subjects from “How To Change A Tire” to “How To Jumpstart Your Car”, visit DefensiveDriving.com’s Safe Driver Resources website!

Check out these sites for more information about defensive driving and business driver safety.

HOW DO BRAKES WORK? Part 3 – Power Brakes and Antilock Brakes

Power Brakes

While drum brakes provide some additional power assist, as we saw in the discussion in Part 2 of this series, disc brakes don’t. In most cars with disc brakes, additional force multiplication is needed in order to make the brakes effective and easy to operate. This power is provided by the vacuum booster; cars that use a vacuum booster are said to have power brakes.

The vacuum booster—a large, flat cylinder—is easy to locate in the engine. (See Figure 10)

 

Figure 10: a vacuum booster

As you can see, the vacuum booster is connected directly to the master cylinder. A hose also connects the vacuum booster to the engine via the check valve. The engine, which generates vacuum naturally as it functions, removes air from the vacuum booster, while the check valve ensures that air doesn’t enter the vacuum booster when the engine shuts off.

The vacuum booster uses vacuum power to increase the force provided by the brake pedal. A shaft passes directly from the brake pedal, through the vacuum booster, to the master cylinder (Figure 11).

 

Figure 11: Inside a vacuum booster

As you can see, there is a diaphragm inside the vacuum booster that separates the end of the booster nearest the master cylinder from the side nearest the brake pedal.

When the brake pedal is released, an ingenious one-way valve opens inside the vacuum booster, connecting the two halves of the booster. This allows the engine to remove air from both halves of the booster, creating a vacuum throughout.

However, as soon as you depress the brake pedal, this valve closes, separating the two sides. At the same time, the front end of the booster opens, allowing air into the front half of the chamber. This creates a difference in pressure between the two halves of the booster, as the air will be at atmospheric pressure on the one side of the diaphragm, while there is no air pressure in the vacuum. As a result, the pressure of the incoming air pushes the diaphragm towards the back of the booster. The diaphragm is connected to the shaft that leads to the master cylinder, so that the force of this push is transmitted to the brake lines via the master cylinder. This process provides a great deal of power; with power brakes, almost anyone can stop a vehicle of any size with ease.

Anti-Lock Brakes

Many modern cars also contain anti-lock brakes, which further help to increase braking effectiveness and safety.

As we discussed above, wheels will “lock-up” and cause a skid if too much braking force is applied too quickly. However, you get maximum braking power just before the wheel locks. For this reason, in order to stop suddenly, especially in wet conditions, you need to approach this threshold without exceeding it.

This is where anti-lock brakes come in. Using a set of speed sensors, the anti-lock brake system’s computer controller can detect when one wheel begins to move slower than the others, i.e. when it is about to lock. At this point, the anti-lock brake controller sends a signal to a valve attached to that wheel’s brake line, which closes to prevent further pressure from being applied. The valve also releases pressure from that wheel. When the tire is no longer decelerating, the valve returns to its starting position, and a pump restores pressure to that wheel.

All of happens very quickly; the system can cycle through this process up to 15 times a second! In some cars, the rapid opening and closing of these valves will produce a “pulsing” feeling in the brake pedal. While this can be disconcerting, it is actually a sign that your anti-lock brake system is keeping your safe.

 Read Part 1 of this series to learn about brake basics. 

To read more on a broad range of subjects from “How To Change A Tire” to “How To Jumpstart Your Car”, visit DefensiveDriving.com’s Safe Driver Resources website!

Check out these sites for more information about defensive driving and business driver safety.

HOW DO BRAKES WORK? – Part 2: Disc Brakes and Drum Brakes

Disc Brakes

While there are several different kinds of disc brakes, the most common is the single-piston floating caliper. You’ll see what this means in a minute. This kind of brake has three main components: the brake pads, the caliper, and the rotor. (See figure 8.)

 

Figure 8: a disc brake

The brake pads are the rough friction surface that is pressed against the rotor to stop the wheel. The rotor is a round plate attached to the hub. The piston presses one brake pad against the wheel, while the caliper presses the other. The caliper is “floating” because it moves in a track that allows it to center itself over the rotor. As the brake fluid fills the cylinder, it pushes the piston to the left; however, it also pushes the caliper to the right. This allows both brake pads to press against the wheel simultaneously. Note that the brake pads don’t actually retract away from the rotor when the piston is released. Rather, they continue to press lightly against the rotor.

Remember that brakes produce a lot of heat. As a result, it’s important that the whole system be vented. Additionally, rotors are constructed with internal vents that dissipate heat. While once made of asbestos, brake pads today are made from various combinations of organic, metallic, and ceramic compounds.

Disc brakes are far more effective than their cousins, drum brakes. However, disc brakes are more expensive to manufacture and need to be made and aligned more precisely. If they come out of alignment, you’ll notice a dramatic shuddering when you brake. For this reason, many cars use disc brakes only on the front brakes. They then use drum brakes on the rear wheels. While drum brakes have more parts and are harder to service, they are cheaper and can easily accommodate an emergency brake mechanism.

Drum Brakes

Like a disc brake, a drum brake uses friction to stop the car. The drum brake is also activated by pistons; in this case, the pistons cause two curved brake shoes to press against the inside of an iron drum, which is in turn located inside the wheel (See Figure 9).

 

Figure 9: Drum brake

Notice, however, that the system is slightly more complex than a disc brake. When the pistons activate the drum brake, the top edge of the brake shoe is the first part to contact the spinning drum. The spinning motion of the drum then pulls the brake shoes outward further, increasing the force with which the shoes press into the drum. As a result, the pistons on a drum brake can be smaller than those on a disc brake.

When the brake is released, the springs in the drum brake pull the shoes away from the drum again; otherwise, the wheels would be unable to spin due to the “pulling” action of the drum against the brake shoes. When driving in reverse gear, the opposite happens, i.e. the bottom part of the brake shoe is pulled against the drum.

As in a disc brake, the brake shoes will wear down over time. A drum brake compensates for this wear by means of an adjuster mechanism.  This mechanism has two parts: a gear that is threaded onto a shaft, like a screw, and a lever (orange in the diagram) which is attached to the brake shoe.

When the car stops in reverse, the lever pulls against the adjuster as the drum pulls the bottom part of the shoe tight against the edge. If the gap between the brake shoe and the drum is too big, then the lever will pull the adjuster enough for it to slide forward a notch, lengthening the adjuster shaft. This pushes the bottoms of the brake shoes outwards, making the gap between shoe and drum smaller.

As you can see from the diagram above, it’s easy to add an emergency brake mechanism to a drum brake. Most emergency brakes are activated by a cable and lever system, like the one pictured above.

While disc brakes can incorporate emergency brakes, these systems are usually more complicated and expensive. In cars with only disc brakes, a second mechanism must be added to the brakes to accommodate the emergency brake function. This can take the form of a second, modified caliper system OR a kind of drum brake, built into the disc brake system.

The Combination Valve

It therefore makes sense to use a combination of disc and drum brakes in a car. Remember, however, that the disc brakes are always in contact with the rotor, while the drum brake shoes are pulled away from the drum walls. For this reason, the drum brakes need to move further in order to make contact with the wheel. In cars with both disc and drum brakes, the metering valve helps to compensate for this difference. The metering valve only allows pressure through to the disc brakes when a threshold pressure is reached. This means that power first goes to the drum brakes. However, the threshold is usually fairly low, so that the disc brakes engage only a little bit after the drum brakes. 

The metering valve is one part of a combination valve, which contains several other valves as well.

The proportioning or equalizer valve accounts for the fact that there is a greater force on the front wheels when you stop. Bear in mind that wheels can only take so much force before they “lock up,” i.e. stop spinning. For this reason, jamming on the brakes too suddenly can cause you to go into a skid. In order to keep the back wheels from locking when more pressure is applied to the front brakes, the proportioning valve insures that more pressure is transmitted to the front brakes than the rear brakes.

The pressure differential valve is used to detect leaks in the braking system. This valve consists of a piston inside of a cylinder. Each side of this cylinder is then attached to one side or the other of the master cylinder. Pressure should thus be equal on both sides of the piston, keeping it in place. If the pressure changes, then the piston will move to one direction or the other. This activates a switch, which causes a brake warning light to turn on in the dashboard.

Read about Brake Basics in the first part of this series.  Read about Power Brakes and Antilock Brakes in the third part of this series.

To read more on a broad range of subjects from “How To Change A Tire” to “How To Jumpstart Your Car”, visit DefensiveDriving.com’s Safe Driver Resources website!

Check out these sites for more information about defensive driving and business driver safety.