In a car what is the hand/foot brake used for, emergencies or parking?
It is for parking .In modern cars the parking brake would hardly help you out in an emergency . It is designed to hold the car and not to slow it down. There just is not enough force generated to slow down a car in motion if something catastrophic were to happen in the main hydraulic system .Furthermore, most if not all parking brakes are at the rear wheels ( I know of only two cars that ever had the parking brakes acting on the front wheels, Saab and Citroen).The last thing you want is the rear wheels locking when travelling at highway speeds. If the rear wheels lock you will lose complete control of the vehicle .When we do safety inspections on cars here in my jurisdiction ,the parking brake is tested by putting the car in Drive and Reverse and releasing the main brakes. The vehicle must stay stationary . I have yet to see a vehicle that stays stationary when applying just a bit of gas .In the not so distant past when most cars and trucks had large drum brakes you could completely lock up the rear wheels by pulling the parking brake lever even at highway speeds. That feature was a lot of fun when driving in the snow because you could actually slide around corners in a controlled skid . Testosterone and youthful idiocy find most dangerous tasks to be fun.But today, most cars have disc brakes at the rear . The application of the parking brake can either happen by an internal mechanism that forces the main caliper piston to clamp the brake pads onto the rotor but the force is many times smaller than the normal hydraulic pressure . The other way is by having brake shoes inside the hat of the rotor, but again these shoes are very small and cannot generate the clamping force necessary to slow down a moving car in a safe manner.Late model cars come with electric parking brakes. They will actually have enough clamping force thanks to electric motors on the rear calipers that will positively lock the wheels, but on those systems you cannot engage the parking brake while the car is in motion. These can truly be called parking brakes. The reason that application while the car is in drive is inhibited by the control module , is exactly because of what I explained above. If the rear wheels lock up at highway speeds you will lose steering and you will become a helpless passenger .
What's the difference between a parking brake and a service brake?
The parking brake is the brake that is designed to "hold" the vehicle. The service brake is the system that is designed to slow down the vehicle and bring it to a stop. Parking brakes are also referred to as "emergency" brakes although , in an emergency they would never slow down a vehicle in a safe manner.The service brake is activated every time you step on the brake pedal and it distributes the braking force hydraulically to the front and rear wheels. 75% front and 25% rear, on average.The parking brake is typically cable operated and applies force to either dedicated brake shoes inside the rear rotor or, through the piston in the caliper. It can be operated by a seperate pedal or a hand lever, usually located between the front seats. Electric parking brakes have a switch as in newer vehicles with electric actuators on the rear wheels. ( electric parking brakes are a very bad idea btw!) Some SAAB models of the eighties and nineties had the parking brakes acting on the front wheels.
Is it safe to use emergency brakes while driving on automatic vehicles?
It is safe to use parking brake during movement. I would recommend to try it out at low speed at first. Then gradually get up the speed (especially if it is not electronically driven).Pulling too hard (or if pushing foot, as some vehicles have that brake there) will lock the wheels and you might lose control.Electronic parking brakes usually brake moderately. Try out.Never pull the brake without holding release button (so you can release as soon as needed).
Are the PARKING brake and Pedal Brake completely separated?
Yes, it's separate. It uses a cable to apply the brake, not the hydraulic system.
How do I stop vehicle when brake fails in automatic transmission?
Say you’re driving on the road normally, when you all of a sudden you encounter a red light, you press the brake pedal—but nothing happens. You then push it all the way to the floor, yet again, nothing—what do you do next? Indeed it’s a terrifying scenario, and it usually happens quite unexpectedly. Typically, brake failure occurs when you lose a lot of brake fluid or you have worn brake pads—thus leading to malfunctioning brakes. If you ever find yourself in this dreadful situation, follow the steps written below to handle it safely.Downshift Right AwayDo not panic: you can handle this situation. The first thing you should do is get your car into a lower gear, as smoothly as possible. This is applicable to both manual and automatic cars. This process will slow down your car, and it may allow you enough time to pull over safely.Things To Avoid:Downshifting too quickly—this could cause a skid.Putting the car in neutral state—it will take away the engine braking effect.Shutting off the vehicle—you won’t have power steering.Assuming you have regular brakes (not anti-lock brakes), you can equally try pumping the brakes quickly—this will help build up brake fluid pressure. If after 3 or 4 pumps your brakes still aren’t functioning,please move on to the next step.Related Post:Definition of Regenerative BrakingApply the Emergency BrakeNext, you should apply the emergency brake. Do not hope for it to bring you to a full stop, but at the very least, it should be able to help you slow down. That said, you need to be aware of where your emergency brake is found—some vehicles use a hand-activated lever, while others have a small pedal to the left of the gas and brake pedals. It’s often a good idea to try your emergency brake when you are driving at a slow speed to test out how powerful it actually is (use an empty parking lot or other area where there are no drivers around).Pull OverSource: What Should I do If Your Brakes Fail?
What exactly happens when brake line on car are cut?
think of it this way you have a garden hose with a sprinkler attached and its on and working now cut the hose does the sprinkler work any more the answer is no some who cut the brake line actually just poke a small hole in it that way it will fail somewhere down the line most newer cars have built a 2 piston master cylender so if you lose 1 brake line you can still stop on the other 2 wheels
Which brake fluid reservoir in a car is connected to the emergency brake, the front or rear?
Thanks for the A2A, Jared.Split systems like that divide the fluid up for use between the front and rear brakes. Your emergency brake is going to be cable actuated, and won’t require fluid.There is an exception I can think of, and this tends to be a thing on some RVs, medium duty trucks, and some equipment. Some of this uses a driveline brake, which can be mounted behind the transmission or before a differential pinion. Some of these systems may be hydraulic actuation (others may be pneumatic). On a system such as this, the hydraulic ones either have their own reservoir (RVs, buses, medium duty trucks) or use fluid from the vehicle’s hydraulic system (equipment which uses hydrostatic drive). The brake is applied by spring pressure, and the hydraulic (or air, in the case of pneumatic systems) pressure is used to hold that off in order to release the parking brake.
Do Tesla cars (Model X, Model S) have emergency brakes?
This is an addendum to my response to Phillip Remaker’s answer. I’ll get to my comment later, but will address what I found out after doing a bit of research on this via various forums.The park button on the end of the right stalk on the steering column will stop the car when the button is pressed and held and the car is not under acceleration (via accelerator pedal, autopilot, or cruise control). This activates a separate electric braking function (which uses screws to depress small brake pads on the rear brakes) from the brake pedal (hydraulic). It’s possible that this could be used in an emergency if the brake pedal did not work, but only if the park button is pressed and held and the throttle is not active. This was tested by a Model S driver at 50 mph and did slow the car to a stop eventually. This is my best summary of a discussion on SpeakEV.com: Emergency use of the parking brake. If you want more details, read through the discussion. (Caveat: I’m not a mechanical-type person, so I don’t guarantee I understood every detail correctly; also, I did have to sort through some conflicting info.)Note about my previous comment: when I accidentally pressed the park button, I was going 65 mph. I was pressing the accelerator and did not hold the button, just pumped it a couple of times. From what I understand both of those would prevent the parking brake from activating.
Why is there no backup brake in cars which the driver can apply in case of brake failure?
There is.First of all, all cars made since the late 1960’s have two independent brake circuits. The brake master cylinder is actually two cylinders activated by the pedal, one of which controls the front brakes and the other the rear. Some cars have the circuits arranged so that one controls front right and left rear and the other front left and right rear. Failure in one circuit does not affect the other. This is why, by the way, the movie/TV plot device of murder by cutting a brake line is nonsense.Second, every car has a parking brake, also called “emergency brake”. This brake functions in a way that is different from main brake. Usually it is actuated by cables and works on the rear wheels.This is a diagram of brakes in a typical passenger car with a front/rear circuitsThis is a diagram of the crosswise circuitsThe emergency/parking brake control in the car usually looks like this:or like this:Some newer cars have an electric parking brake, but that is still fairly rare.Parking brakes have been in cars for at least 100 years.