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Wednesday, January 18, 2012

How To Stop Car Without Brake

One of standard procedure before starting a car is to step on brake pedal, ensure gearshift in neutral position, it is useful to check brake condition and ensure vehicle will not move when engine is starting. But often times we found out that the brake did not function properly when we're running a vehicle.

Usually brake will not fail instantly. If any brake fluid leaks on front brakes, then brakes on rear wheels are still able to function, though not with a good grip. Similarly, if the rear brakes leak, front brakes are still functioning, though not as good as normal. This is because the front brake system and rear brakes system are not in a single system. Although front brake master cylinder and rear brake master cylinder are joint together, but the piston is different, so if the front brake or rear brake leaks, brake hydraulic pressure loss does not occur immediately or all at once.

There is also a system that has a diagonal hydraulic system, which has right front brake and left rear brake are using same hydraulic system, and the left front brake uses the same hydraulic system with the right rear brake. So if there is a leak in the hydraulic brake system on the right front wheel, the left front brake and right rear brake can still be used to stop the vehicle as soon as possible.

Some vehicles have brakes with dual hydraulic, where one hydraulic system is completely separated or independent with the other hydraulic system. Each system operates brake on three wheel, two front wheels and one rear wheels, it is like two triangles. So if brake on one wheel does not work properly then the other three wheels are still working well to stop vehicle as soon as possible.

If the hydraulic brake system is leaking, the pedal will mushy and pedal travel is longer then ussual. In a bad condition, brake pedal can be stepped down to the floor. Usually by pumping the pedal several times, the brakes will get back to work for a while.

If the pedal mechanism jammed, the brakes feel hard when stepped on and short pedal travel.

Drum Brakes
On vehicles with all wheels use drum brakes, such as truck, bus, pick-up, the brakes will have less grip after going through water. This is because layer of water trapped inside drum. To remove this water layer, then run the vehicle with half applied brake. Friction between drum and shoes produces heat and evaporate water layer in drum. Release brake pedal after you get normal grake grip.

You can also apply half brakes before and during your vehicle entering flood, but additional load as moving in flood and stepped on the brake will cause the engine to stop in that flooded road. It would be difficult to start the engine as electrical systems wet, especially for vehicle with gasoline engine.

If you activate the parking brake half, just before entering and while passing through flood, it will not create as much load as when applying brakes. But only rear brakes are dry, while front brakes are wet. So when braking, the rear wheels will possibly to get slippage and the rear end is moving to the left or right (sliding). When rear wheels slip, then a small movement of steering wheel will make the car turn more sharply than normal (oversteer).

On disc brake the water layer is thrown out because of centrifugal force as the wheel rotates, then the brake will dry by itself.

No Brake at High Speed
If you feel that the brakes do not work normally, then immediately stop the vehicle. For the sake of your safety and other people, do not try to gamble with the brake, it is better to have car with engine won't start, than you are speeding with no brake.

But how to stop vehicle that is running fast and with brakes do not work normally??

As in any emergency situation, the main procedure is do not panic.

Emergency Warning Sign
Turn on hazard lights. Keep in mind, when the hazard lights are turned on, then turn lamps do not work. So if you need to inform other drivers that you want to change direction, then turn off hazard lights and switch on turn signal so that other motorists know that you will change direction.

Sound the horn when you need to clear your way, blinking head lights can also help. The sound of horn, blinking headlights, and hazard lights are usually enough to make other motorists understand that you are in an emergency situation.

Brake by Compression
Lower gear (down shift) gradually while throttle pedal released, from 5 to 4 to 3 to 2 and to 1. Vehicle speed decreases with engine compression pressure (engine brake).

It wont be easy to shift to lower gear suddenly, for example from 5 directly to 1, as too much difference in gears speed, the gears will be difficult to engage. You will waste valuable time just to try to down shift the gear from 5 directly to 1. And it will cause damage to the vehicle mechanism. Sudden gear reduction may cause engine overspeed, or engine revolution beyond its limits (over rev). Overspeed on diesel engine can cause piston break, connecting rod will hit cylinder wall and the engine will break. Look at tachometer or RPM meter to ensure the engine rotation is still within safe limit.

On vehicle with rear-wheel drive, sudden gear reduction can cause the rear wheels slip, so that the rear of the vehicle skidded and difficult to control. When rear wheels are slipping, a small steering wheel movement will make the car turn more sharply than it should be (oversteer).

On vehicles with front-wheel drive, sudden gear reduction can cause front wheels slippage. When front wheels are slipping, the vehicle tends to move straight and steering wheel needs to be turned more than normal when turning (understeer).

For vehicles with automatic transmissions, the shifter usually can be directly shifted from Drive to 1, transmission control will automatically do graduall gear change to lower. But it must still consider the effect of wheel slippage as described above (oversteer and understeer), especially if the road slippery.

Hand Brake or Parking Brake
Hand brake or parking brake can be used to slow the vehicle. Do not use the parking brake until the rear wheels locked and skid. Because it can cause oversteer, both on front-wheel drive vehicle, or on the vehicle rear wheel.

Cruise Control
Make sure the cruise control in off position. Usually the cruise control would soon deactivated if the brake pedal or clutch pedal stepped on, but as it is in emergency situation we need to ensure that the switch is positioned off.

Retarder, Jake Brake (Jacobs Brake)
Some vehicles such as trucks, equipped with a retarder to slow the vehicle and it is attached to the transmission. Retarder is usually used on the descent road, where too long brake usage will cause brakes overheating. Retarder can be used in a long time like going down the mountain. Retarder effectiveness decreased at low speeds, because the retarder is fan blades that rotate in oil bath. Some vehicles use electromagnetic retarder. Retarder can prevent engine overspeeding when using engine compression to slowdown the vehicle.

Vehicles with diesel engines were equipped with jake brake, which slows the vehicle by engine compression and the engine rotation is slowed down by the jake brake. Jake brake is a mechanism to leak exhaust valve at the end of piston compression stroke, to avoid the compressed air push piston downward after compression stroke is completed. Without jake brake compressed air will act like spring that push the piston down after compression stroke.

Use retarder and jake brake if your vehicle is equipped with these equipment.

Take advantage of Road Shoulder
Road with shoulder that have gravel or sand, can be used to slow the vehicle. Steer your vehicle to the road shoulder. On the racetrack it is commonly referred as gravel trap.

Road shoulder like the above image, with grass, weeds, and bushes can also slow the vehicle. Choose weeds and bushes that are not too high, with maximum height about same to vehicle floor or about 15 cm or 6 inches for the sedan. For tall vehicles such as jeeps and trucks, the bushes or weeds may be higher. This consideration because we can not clearly see any objects that lie behind the weeds and bushes. There could be a large rock or gutters that can cause severe damage, a vehicle can be tipped over if stuck in a ditch at high speeds.

Once the vehicle stops completely, check your brakes. If it can not be repaired, then you should have your vehicle towed. If hand brake / parking brake can not be functioned, then engage first gear to prevent vehicle moving when parked. But if parking on slope where there is possibility engine compression cannot hold vehicle stand still, add two wheel chocks to ensure vehicle does not move forward nor backward.

Remember: Do not Gambling With Brake.

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