Go Back   Team-BHP > Under the Hood > Technical Stuff


Reply
 
Thread Tools Search this Thread
Old 18th March 2011, 21:37   #1
BHPian
 
layndrivr's Avatar
 
Join Date: Feb 2011
Location: New Delhi
Posts: 25
Thanked: Once
Default What to do in case of Brake Fail !!

hi,

a few days ago, while descending a flyover on delhi, driving my 2002 M800 (in pristine condition, at least i thought so), i started to press the brake pedal to slowly reduce speed, i was doing between 65 - 70 kmph, and i just did not get any feedback from the brake. never having experienced this before, i got startled and to say the least my heart raced ... i pressed the brake harder instantly and for around 1-2 secs there was no response, but then in an instant it braked !! i realized that by the time it stopped i had also pulled the handbrake.

those were the longest few seconds I've experienced.

I'm planning on taking the car to the workshop this weekend and get it checked. although after that, i did not feel any loss in braking power.

The larger question here, i wished to ask, is that in the unfortunate event of a brake failure, i realize these days cars come with much sophisticated systems, what is the safest way to bring the car to a halt.

in my little experience, think the below could work:
1. downshifting gradually
2. handbrake

between highway and city driving, what would you recommend?
and are there any early warning signs, which a driver could identify?

(mods: I've searched the forums, there is no dedicated thread for this, although there are multiple on specific brake failure incidences. either way, please move to appropriate location,if needed)
layndrivr is offline   Reply With Quote
Old 19th March 2011, 00:00   #2
Senior - BHPian
 
bluevolt's Avatar
 
Join Date: Jan 2011
Location: New Delhi
Posts: 2,963
Thanked: 2,211 Times
Default Re: What to do in case of Brake Fail !!

Handbrake is connected to the rear brakes. If rear brakes fail, handbrake would be of no use. In such unfortunate event one should downshift. One should also try to pump the brake pedal as this may build enough pressure to stop the vehicle. Never turn off the engine as this may disable power/hydraulic steering system also.

PS - pray to god so that such unfortunate event never take place.

Last edited by GTO : 28th December 2011 at 11:43. Reason: Removing point on reverse gear as it is outright dangerous & ineffective
bluevolt is offline   Reply With Quote
Old 19th March 2011, 00:12   #3
Distinguished - BHPian
 
SS-Traveller's Avatar
 
Join Date: Jan 2009
Location: New Delhi
Posts: 6,618
Thanked: 10,789 Times
Default Re: What to do in case of Brake Fail !!

1. Pull up the handbrake - gently, not with a jerk, a sharp tug can put your car into a spin if it is going fast.
2. Shift down 2-3 gears - 5th to 3rd, 4th to 2nd, even 5th to 2nd, and finally to 1st (most cars can do it since 1st gear is synchronised, but old Ambys & Fiats can't, because they lack synchromesh 1st gear). Release the clutch smoothly without your foot on the accelerator. Turning off the ignition will make the steering and brakes lose assistance in a PS-equipped car with servo boosted braking - don't do it.
3. Keep pumping the brake pedal rapidly and firmly. Most cars have dual circuit braking, and you can lose braking on 2 wheels - rare to have total braking loss. Also, in cars with servo-assisted brakes (not on the M800), a servo failure will make the pedal wooden and hard. Stand up on the pedal, if need be.
4. Steer away from obstructions, and scrape up against a footpath or wall to lose speed and bring the car to a stop. A dented car is better than a injured/dead driver.
SS-Traveller is offline   Reply With Quote
Old 19th March 2011, 00:53   #4
Senior - BHPian
 
harishnayak's Avatar
 
Join Date: Sep 2006
Location: DELHI
Posts: 1,388
Thanked: 116 Times
Default Re: What to do in case of Brake Fail !!

May not be too OT but i would like to share my experience of an accident which caused my brakes to fail and how i managed to stop the car.

While descending from the Radisson flyover in Delhi at about 3:00 am at speeds of 70 kmph in my alto LX i was hit by a speeding esteem ( taxi ) who was doing over 100 kmph.

The impact was such that my cars 2 rear wheels went on his bonnet ( tillabout half the bonnet ) and when the car came down i pressed my brakes and the pedal just caved in . ( My initial thought was what SStraveller suggested ie to scrape the divider to slow down however i acted swiftly and switched the car off and put the 3rd gear and swerved to left and halted after about 50 meters or so ).

The main impact was on the rear left wheel which also disabled the handbrake. I was lucky to walk out alive out of this accident as i was properly belted and there was no vehicle coming from behind.

Total damage 45 K
harishnayak is offline   Reply With Quote
Old 19th March 2011, 01:38   #5
BHPian
 
Join Date: Jan 2009
Location: Hyderabad/Mysor
Posts: 155
Thanked: 58 Times
Default Re: What to do in case of Brake Fail !!

I agree with most of what traveller said. Here's my two cents anyways.

1. A lot of cars come with drums at the rear. And since the handbrake is connected to the rear wheels, and drums are really not that effective, i wouldn't rely on them entirely. On a M800, that might work because of it's light weight but i shudder to think of how useless it would be on a toyota fortuner. It's rather useless on my vista as it is. So, i recommend that you familiarize yourself with how your handbrake behaves on an empty road at progressively higher speeds if your car comes with rear brakes.

2. If your comes with rear discs, yes, do exactly what traveller said, pull it slowly. It's entirely possible to lock both rear wheels by pulling too hard on your handbrake too hard. The loss of traction leading to loss of control can be catastrophic. Again, familiarize yourself with how your handbrake behaves.

3. About downshifting- the whole point of downshifting is to use engine braking. Engine braking is higher at higher engine rpms and hence, you downshift.

So, how fast are you supposed to downshift? It all depends on how much you are willing to damage your mechanicals in order to stop the car. Supposing you have a free road in front of you, then i'd recommend switching into the gear whose max speed in gear is just higher than the speed you are at. Supposing you are at 70km/hr in 5th, 2nd tops out at 80 and 3rd at 120, 2nd is the right gear to go two. If you are unsure about these values/ can't think of them in the heat of the moment, two gears down is a good rule of thumb (unless you are redlining your engine, in which case i'm pretty sure you'll be very familiar with where your gears top out).

3. What about the brake?
It all depends on what type of brake failure it is.

If it's brake fade, then stand on the brake like traveller said and apply all the above steps.

If it's catastrophic brake failure, and you are pumping the brake with no effect whatsoever, do it anyway, just in case.

4. So, what of switching off the engine? Don't do it if you are travelling at high speeds. Since most of our cars are front wheel drive, that could cause the *front* wheels to lock. Your steering wheels getting locked is a very very BAD THING. Once you get locked into that kind of slide, with your engine switched off, regaining control in time is improbable. It's either crash or you get lucky and you stop.

Also, a slide itself might just be getting lucky. If you were traveling at a high speed, and your car has a high center of gravity, that's just the perfect recipe for a casino royale style crash (rolling over).

5. Also remember that the common reflex of pressing the clutch in emergency situations is usually a bad thing if your brakes fail.


Signs of brake failure.
1. AFAIK there's no good sign to predict a catastrophic failure. If your brake pedal loses all resistance suddenly, this is the likely cause. Keep your car serviced, make sure you don't use worn out, retreaded tires and keep your head level.

2. Loss of brake assistance. As traveller mentioned, modern cars come with servo assisted brakes. If your brake suddenly becomes wooden, this is the likely cause. Just go stand on your brake pedal as hard as you can and apply any other techniques as necessary.

3. Brake fade. This occurs if you have been riding your brake pedal over a long slope. The brake seems to have normal resistance but the brake doesn't seem to have the usual effect and it gets progressively worse. If you detect this happening, stop riding on your brake, use your engine braking to slow your car down and stop at a safe spot for (not sure here, i've never let this progress too far when i tried to artificially create this, is half hour ok?). Then continue, make sure to use your engine braking afterwards to avoid a repeat.


This all might be a little haphazard, but i just put down everything that came to my head without much organization. Any corrections would be welcome.

Disclaimer-
I'm in no way an expert on this topic. This is all just research and personal opinion
nukeblitz is offline   Reply With Quote
Old 19th March 2011, 10:33   #6
BHPian
 
changaez's Avatar
 
Join Date: Sep 2010
Location: France
Posts: 72
Thanked: 5 Times
Default Re: What to do in case of Brake Fail !!

Another tip, when you realize that breaks are failing. Drive Zig Zag rather than straight line, this helps the ground friction to slow down the vehicle. There is a video on Youtube which actually demonstrates the slowing down because of the Zig Zag.

cheers
changaez is offline   Reply With Quote
Old 19th March 2011, 11:03   #7
dot
Senior - BHPian
 
dot's Avatar
 
Join Date: Dec 2007
Location: Ban Chang
Posts: 1,681
Thanked: 714 Times
Default Re: What to do in case of Brake Fail !!

A very important discussion, indeed. The tips can be a lifesaver when such a black swan event occurs.

Mods, do consider to include this in Advice or an appropriate section.
dot is offline   Reply With Quote
Old 19th March 2011, 11:15   #8
BANNED
 
Join Date: Aug 2010
Location: Greater Bangalore
Posts: 421
Thanked: 31 Times
Default Re: What to do in case of Brake Fail !!

Quote:
Originally Posted by changaez View Post
Another tip, when you realize that breaks are failing. Drive Zig Zag rather than straight line, this helps the ground friction to slow down the vehicle. There is a video on Youtube which actually demonstrates the slowing down because of the Zig Zag.

cheers
That would be real dangerous considering danger to other people around.

In all cases, once the brake fails, we do have the handbrake working irrespective of the conditon of the brakes.

I faced a similar issues with my friends santro some time back, all i did was

1) Downshift to first gear again and again
2) Keep tugging the handbrake lever at intervals

Thats it, i could manage to get the car home and next day to the service station.
EARTHed is offline   Reply With Quote
Old 19th March 2011, 11:24   #9
Senior - BHPian
 
shankar.balan's Avatar
 
Join Date: Apr 2008
Location: BLR
Posts: 8,027
Thanked: 5,325 Times
Default Re: What to do in case of Brake Fail !!

the only way to bring a car to a halt when its brakes fail is to literally ram it into the lowest available gear in the shortest time possible.

As it slows down, one has to try and push it into first gear while pulling the handbrake as it slows down to the lowest possible speed. If one pulls the handbrake while travelling at high speed one is likely to end up hurting one's self as well as any other road users who may be around at the time.

If all else fails, try and bring the car to a halt by crashing sideways into the road side barriers - there's no other way out.

this is why, while engaged in highway driving it is a good practice to now and then pump the brake pedals just to ensure that everything is working smoothly. And of course, keeping your vehicle in the best maintained condition as possible, at all times.
shankar.balan is offline   Reply With Quote
Old 19th March 2011, 11:39   #10
Senior - BHPian
 
Join Date: Apr 2008
Location: Dombivli
Posts: 2,626
Thanked: 1,191 Times
Default Re: What to do in case of Brake Fail !!

If you are descending, for e.g. say from a flyover, simply downshifting won't help, because the wheels will then simply increase the RPMs of the engine, not allowing for enough engine braking. When I downshift on a flat road, I am able to slow down because of the engine braking. However on a descent I can't because depressing the clutch for downshifting allows the car to slide forward at a greater momentum and when I complete the downshift the wheels just increase the engine RPMs, resulting in the car either maintaining or slightly increasing the speed.

The first thing you should be doing when you notice you are losing the braking power is to pump the brake pedal hard (depress it and then release it, depress it and then release it as quickly as you can for about four to five times). When this doesn't work still, ram it down as hard as you can. Obviously when you are operating the brake pedal, you have taken your foot off the accelerator. If it's a problem with the hydraulics, pumping the pedal vigorously a few times should restore the braking power.

Use the handbrake by lifting it probably a couple of notches or a little more. Don't pull it all the way up, for reasons mentioned above. The handbrake is cable-operated, so even if the car doesn't have any brake fluid in the system, the handbrake should engage the rear wheels and slow down the vehicle. While the rear drum brakes are not as effective as the front disc brakes in sheer stopping power, they can surely help lose speed.

Try downshifting, skipping a gear might be a good idea. So if you are in fifth, try shifting down to the third, all the while making sure you have the brake pedal depressed, and use the clutch very quickly so as to downshift as quickly as you possibly can.

Steer the car to the side of the road, or if that's not possible keep steering it straight ahead. If you can, switch on the hazard lights (headlights if possible), so that others may know something is wrong with your vehicle. Make sure you are steering the car, and don't let the car wander off its intended path.

Most important of all, don't PANIC! Panicking is more likely to cause an accident than the actual brake fail.
honeybee is offline   Reply With Quote
Old 19th March 2011, 11:43   #11
Senior - BHPian
 
mdsaab's Avatar
 
Join Date: Jul 2008
Location: Pune
Posts: 1,624
Thanked: 446 Times
Default Re: What to do in case of Brake Fail !!

A very relevant and important thread.
Fellow bhpians have already mentioned all that i know.
So have nothing more to add. Ofcourse shifting to lower gears also applies on an AT transmission.
mdsaab is offline   Reply With Quote
Old 19th March 2011, 12:05   #12
BHPian
 
Join Date: Sep 2010
Location: Bangalore
Posts: 828
Thanked: 113 Times
Default Re: What to do in case of Brake Fail !!

Your car will have a braking system that depends on the engine being switched on to work effectively. Try this - press the brake pedal then turn on the ignition. You will feel a pressurizing sensation on the brake pedal.

For this reason, your car manual may also tell you never to switch off the engine and coast downhill.

--Ragul
Ragul is offline   Reply With Quote
Old 19th March 2011, 12:22   #13
Senior - BHPian
 
bluevolt's Avatar
 
Join Date: Jan 2011
Location: New Delhi
Posts: 2,963
Thanked: 2,211 Times
Default Re: What to do in case of Brake Fail !!

We are discussing here what do do in case of brake fail and we have quite a few basic steps to follow if such event happens. But the important question is that why brakes actually fails and how to prevent them from failing?
bluevolt is offline   Reply With Quote
Old 19th March 2011, 12:54   #14
Senior - BHPian
 
Join Date: Sep 2007
Location: New Delhi
Posts: 3,083
Thanked: 252 Times
Default Re: What to do in case of Brake Fail !!

Quote:
Originally Posted by nukeblitz View Post
.....
4. So, what of switching off the engine? Don't do it if you are travelling at high speeds. Since most of our cars are front wheel drive, that could cause the *front* wheels to lock. Your steering wheels getting locked is a very very BAD THING. .....
NukeBlitz, this is completely incorrect! Switching off the engine will most certainly not cause the front wheels (or rear wheels in rear wheel drive cars) to lock!
Switching off the engine is not advisable for different reasons, like loss of power assist to the steering and servo-assisted brakes.
anupmathur is offline   Reply With Quote
Old 19th March 2011, 13:08   #15
BHPian
 
Daewood's Avatar
 
Join Date: Dec 2009
Location: Chennai
Posts: 943
Thanked: 223 Times
Default Re: What to do in case of Brake Fail !!

Quote:
Originally Posted by honeybee View Post
However on a descent I can't because depressing the clutch for downshifting allows the car to slide forward at a greater momentum and when I complete the downshift the wheels just increase the engine RPMs, resulting in the car either maintaining or slightly increasing the speed.
Wouldn't the engine RPM come back to lower levels as programmed in the ECU after the momentary initial increase, since the feet is not on the accelerator?
Daewood is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Temporary brake fail in Honda City gou Technical Stuff 33 13th August 2011 14:31
Brake fail causes riots in Khopoli nawabnabeel Street Experiences 20 9th June 2009 00:26


All times are GMT +5.5. The time now is 15:08.

Copyright 2000 - 2017, Team-BHP.com
Proudly powered by E2E Networks