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Old 14th June 2011, 15:09   #46
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Default Re: Emergency driving - Without brakes

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No leaks. The brake oil is there and rarely needs to be topped up. Once the vacuum is used up the brake pedal just sinks, as though there is no brake oil! As I have lived with it for 10+ years, I have stopped thinking about it.
Dude, it seems to be a problem with the master cylinder. According to me, the brake pedal should not sink if its a problem with the vacuum booster. I suggest, get the master cylinder checked and if required repaired or replaced.
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Old 27th June 2011, 01:08   #47
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Default Re: Emergency driving - Without brakes

@Aroy:As stated by TI, there def is a prob with your braking circuit & you shld have it checked out soon.
Reason why I say this?
I too drive an Esteem & have tested braking w/o vacuum assist by switching off the engine on a down slope & repeatedly braking & letting go, 8 to 10 times & then holding the brake pedal down till the car stopped.
At no point did the brake pedal just sink down & lose all braking ability, tho a lot of effort had to be used to depress the brake pedal.
@Sudev-are you the Sudev who is a long time friend of my cousin Rohit Tandon?( for some reason I am unable to PM you to ask this Qn)
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Old 28th June 2011, 13:17   #48
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Default Re: Emergency driving - Without brakes

@Kamal : yep. PM's working as I got few of them over week end.
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Old 30th June 2011, 23:44   #49
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Default Re: Emergency driving - Without brakes

@Sudev-OK.Nice.
Re PM's, I meant that I'm unable to PM since I don't find a PM tab when I log in.Have written to Mods a couple of times but no response from their end yet.
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Old 1st July 2011, 01:30   #50
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Default Re: Emergency driving - Without brakes

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@Sudev-OK.Nice.
Re PM's, I meant that I'm unable to PM since I don't find a PM tab when I log in.Have written to Mods a couple of times but no response from their end yet.
OT - But Kamal, you need at-least 25 posts to be a bhp'n and thereafter get the PM facility.

Check - http://www.team-bhp.com/forum/announ...-benefits.html (Explanation of Membership Levels (Newbie, BHPian etc) & Their Benefits)
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Old 1st July 2011, 20:11   #51
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Default Re: Emergency driving - Without brakes

Oh.OK.
Thanks for the clarifications,dhanushs.
Guess I'll have ti start posting more.
But, seeing the level of expertise & knowledge in this Forum, I feel like such a novice!
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Old 9th September 2011, 14:54   #52
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Default Re: Emergency driving - Without brakes

Great information here. Good initiative, Sudev. My Dad had told me the same thing during his "theory" class before letting me take the wheel some 10 years ago.

Now, I have a somewhat noobie question which might be slightly off topic. Under normal circumstances, how would you define engine braking? Is it shifting down through the box and engaging each gear for a while during braking, or is it refusing to disengage the clutch until the very last possible moment to prevent stalling, so that the engine assists the brakes? I practise the former whilst riding my bike as the gears are sequential but I feel the latter is better in a car, as the earlier method may take too much time.

Any guidance forthcoming?
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Old 9th September 2011, 15:15   #53
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Default Re: Emergency driving - Without brakes

Engine braking happens the moment you ease off the accelerator. That is why the car slows down!

But there are degrees to things, so we must go a step further and say that, in 5th gear, it is barely noticeable, in 4th it is noticeable, in 3rd it is considerable.

I've always said that the lower the gear the more the engine braking, but I've taken correction from Team-BHP members re diesels (and I should know, as I drive one) where, at slow speeds, the engine torque is so considerable that it requires quite a heavy foot on the brake pedal to stop the car shooting ahead in 1st gear.

Whether we change down or not depends on anticipation. A true emergency stop gives us no time for anticipation, just standing on the brake. In normal driving, spotting hazards or potential danger says to change down, as then one has greater control over the car, either for slowing down or for accelerating.

Approaching a sharp corner suggests changing down, as engine braking is less likely to cause a skid.
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Old 9th September 2011, 19:19   #54
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Default Re: Emergency driving - Without brakes

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Originally Posted by Tejas Ingle View Post
If you are caught in life threatening situation without brakes, feel free to engage reverse gear. This applies to both manual & auto transmission. In manual, it will require some force to engage. Once engaged, rev hard (hard enough to prevent the engine from stalling) and release the clutch. In auto, engage R and rev. This will screw your transmission but save your life...

wont this just break the gearbox??

i am not sure the vehicle will stop at all..
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Old 9th September 2011, 22:05   #55
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Default Re: Emergency driving - Without brakes

First off all,reverse gear wont engage on any car of todays era while the vehicle is moving(anything above 20kmph) The engaging surface of the teeth on reverse gear is designed that way.
If you manage to engage it anyhow,you are loking at broken main gearbox shaft instantly.
Thereby loosing any enginebraking you would be getting.
I am not sure of an autobox though.
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Old 10th September 2011, 06:29   #56
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Default Re: Emergency driving - Without brakes

Engine braking - When you let go the accelerator engine does not get fuel and the piston stroke only works against vacuum of pulling air (which in normal cycle would have been expanding because of combustion and pushing the piston).

So leaving car in gear and not pressing clutch will de-accelerate the car.

How much braking? Depends on gear ratio. More the ration more is the braking. So faster you are able to reach the first gear more you will stop.

Emergency braking is all about reducing speed. You may not be able to avoid hitting something but you will do so with much less speed and consequently much less damage compared to hitting at full speed. Also at reduced speeds you can attempt evasive actions which are not possible at higher speeds.

Stunt drivers and such are able to put reverse gear while moving forward. But notice carefully they are able to do this only when the wheels are skidding (technically wheels are stopped still) and then releasing the clutch. They do it fast but this needs brakes to be functioning really well. We are discussing when brakes are not functioning 8-(
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Old 10th September 2011, 09:30   #57
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Default Re: Emergency driving - Without brakes

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Originally Posted by sudev View Post
Engine braking - When you let go the accelerator engine does not get fuel and the piston stroke only works against vacuum of pulling air ...

... So leaving car in gear and not pressing clutch will de-accelerate the car.
.... Till the idle rpm. Afterwhich, in all modern cars, ECU will try to pump fuel and maintain the idle rpm.

In any case, during emergency braking its never advisable to wait till idle rpm, to downshift to the next gear. Downshift as fast as your car can.
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Old 10th September 2011, 12:13   #58
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Default Re: Emergency driving - Without brakes

Again repeating a question posted earlier -

Can we put reverse gear and let go ..[I personally think it is not possible but want experts to advice]
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Old 10th September 2011, 13:15   #59
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Default Re: Emergency driving - Without brakes

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Originally Posted by headers View Post
Again repeating a question posted earlier -

Can we put reverse gear and let go ..[I personally think it is not possible but want experts to advice]
Simple answer - NO.

The reason is
. Reverse gear is not synchromesh in cars, hence will not synchronize shifting from forward gears to reverse at any but extremely low speed (< 5km/h)
. The teeth on the first and reverse gears are generally straight and not helical, which means that they have to be engaged gently, else they break. Helical gears can mesh easily.

The above may not be true for stunt cars, where the gearboxes are designed to execute various stunts.

I use engine breaking regularly, as a means to
. wear the breaks less.
. be prepared for emergencies, when brakes fail.

Once you get used to it it is very easy to shift down very fast to achieve excellent braking. In fact most of the times I have to press the brakes to indicate that I am braking, as most people rarely notice the vehicle in front of them slowing down without brake lights indicating so! (some moron immersed in his own thoughts may even rear end you, and claim that there was no indication of you braking in his defence)
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Old 10th September 2011, 21:54   #60
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Default Re: Emergency driving - Without brakes

Quote:
Originally Posted by headers View Post
wont this just break the gearbox??

i am not sure the vehicle will stop at all..
Quote:
Originally Posted by dustom_99 View Post
First off all,reverse gear wont engage on any car of todays era while the vehicle is moving(anything above 20kmph) The engaging surface of the teeth on reverse gear is designed that way.
If you manage to engage it anyhow,you are loking at broken main gearbox shaft instantly.
Thereby loosing any enginebraking you would be getting.
I am not sure of an autobox though.
Quote:
Originally Posted by headers View Post
Again repeating a question posted earlier -

Can we put reverse gear and let go ..[I personally think it is not possible but want experts to advice]
Quote:
Originally Posted by Aroy View Post
Simple answer - NO.

The reason is
. Reverse gear is not synchromesh in cars, hence will not synchronize shifting from forward gears to reverse at any but extremely low speed (< 5km/h)
. The teeth on the first and reverse gears are generally straight and not helical, which means that they have to be engaged gently, else they break. Helical gears can mesh easily.

The above may not be true for stunt cars, where the gearboxes are designed to execute various stunts.

I use engine breaking regularly, as a means to
. wear the breaks less.
. be prepared for emergencies, when brakes fail.

Once you get used to it it is very easy to shift down very fast to achieve excellent braking. In fact most of the times I have to press the brakes to indicate that I am braking, as most people rarely notice the vehicle in front of them slowing down without brake lights indicating so! (some moron immersed in his own thoughts may even rear end you, and claim that there was no indication of you braking in his defence)
Engaging reverse gear while the car is in motion is very much possible. True, it will ruin your gear box, but thats preferable to going down in a valley. I too didn't beleive this earlier but I have seen a demonstration on Discovery Turbo where the stunt driver reversed an average looking estate out of a steep slope without using any brakes. After managing to shift, he flored the pedal and managed to get out of the ditch. Ofcourse, the car was scrapped after the demo. But you can definately give it the LAST try in life threatening situations.
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