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Old 28th March 2011, 16:29   #61
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Default Re: What to do in case of Brake Fail !!

^^ Non firing engine with the transmission in gear, and foot off the clutch pedal would create more braking as compared to a firing engine under the same set of conditions, IMO.
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Old 28th March 2011, 16:38   #62
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Default Re: What to do in case of Brake Fail !!

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Originally Posted by honeybee View Post
Non-firing engine means you have to shift to either neutral or keep the clutch depressed. In both cases, the vehicle is free to roll down the road guided only by gravity, while you have no control over its speed whatsoever. I don't see what's the wisdom in that.
I have also explained that earlier, clearly. Switch OFF the ignition while the engine is still in gear.

And non-firing engine does not necessary mean the gear is disengaged.

OK, now let me try to explain one last time:

Here, what I meant is downshift, and ONLY turn off ignition. Turning off ignition does NOT mean; depress the clutch or engage neutral. Just turn the key to ACC position if you have one so that the steering does not lock.

This way, as the key is in the off position, there will be no spark, and hence NO combustion. But the wheels will be powering the engine, so it will continue to turn. As the wheels are turning the engine, which is not firing (No combustion) there will be more engine braking, than when the key is ON.
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Old 28th March 2011, 17:09   #63
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Default Re: What to do in case of Brake Fail !!

I am not sure I understand this whole thing correctly. To the best of my knowledge, if the engine isn't cranking when the wheels are turning (and a gear other than neutral is engaged), it will start cranking, just as in case of a push-start when the battery goes dead. Has anyone ever actually tried doing this??

I have started my M800 many times by shifting it to second gear and having someone push it with the key in the ACC position (battery gone kaput). I was also told that it's easier to push start the car in second gear. The procedure is essentially you shift to second, the car starts being pushed, and as soon as you pick up a little speed, you ease out the clutch. The spinning wheels make contact with the gear which in turn makes the engine turn and CRANK.

Last edited by honeybee : 28th March 2011 at 17:11.
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Old 28th March 2011, 17:12   #64
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Default Re: What to do in case of Brake Fail !!

I gathered all these points from discovery channelís show, worst case scenario hosted by Bear Grylls. These are his actual words.

1. Donít turn off the engines.

2. At high speed donít downshift or pull the emergency brakes as you run the risk of dropping your transmission and losing control.

3. Keep your thumbs on the outside of the steering wheel - bear grylls explained that the thumbs might break in an emergency when the steering wheel is spinning (Pardon me, as I myself didnít understand this point properly)

4. If the car is travelling more than 20 mph then try to create friction in the tyres by zigzagging.

5. Use dirt, gravel, guardrails and shrubbery on the side of the road to slow the vehicle down.

6. Donít panic.

If anyone is interested in watching the video, its season1 Ė episode 5. The video is pretty good. It also features how to survive a physical assault.
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Old 28th March 2011, 17:24   #65
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Default Re: What to do in case of Brake Fail !!

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Originally Posted by honeybee View Post
The spinning wheels make contact with the gear which in turn makes the engine turn and CRANK.
Yes!!.. Exactly, that's the point. but then, keep the key in the OFF position, so that crank keeps on turning, without actually 'starting'(firing) the engine.

For the engine to 'fire' you have to turn the key to ON position.

Now I hope you understand better?
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Old 28th March 2011, 17:33   #66
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Default Re: What to do in case of Brake Fail !!

Yes, now I understand better, thanks

I am still not convinced it's a better way of slowing down the car, but it could be a good fallback method, like when everything else fails, try this one.
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Old 29th March 2011, 07:47   #67
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Default Re: What to do in case of Brake Fail !!

Brake fail can be categorised in to two sections, guys please add more in case you think so.

1) Complete loss of braking ability.
2) Brake fade

I have experienced the second part , as i forgot to pull down my handbrake.I am sure lot of us have done this.

Luckily it happened on highway and i stopped at side ( after a biker gestured towards my rear tyre ) and noticed that my rear left tyre had lot of smoke!!

But it was only rear left tyre ( Mech had not done the handbrake work properly, hence it was only working for rear left tyre )

I pushed the handbrake down and started driving instantly thinking it might cool down the rear drums - BIG MISTAKE.

I had to stop before a Toll naka, and to my horror the pedal had sinked completely.

But since it was brake fade, i still had some stopping power left and lot of distance to stop, but it was very very scary and the first thing which came to my mind was downshifting.

But i slowly recovered complete braking ability later on.

Lastly the car was a Premier Padmini 1993 Petrol - Column mounted gear shifter! very difficult car to downshift!

In case of total loss, its very crucial to keep a calm mind and make correct decisions.I think this is the most difficult part since PANIC sets in with most of the drivers.
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Old 29th March 2011, 08:35   #68
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Default Re: What to do in case of Brake Fail !!

That explains it. The Padmini had drum brakes all around, which takes much longer to stop anyways. So when the rear liners failed (because the handbrake was engaged), you lost half the braking power.

With modern cars with front disc brakes, even if you engaged the handbrake and managed to fade the rear brake liners, the real stopping power comes from the front discs. In this case you would still be able to stop within the safe distance. Of course you shouldn't be jamming onto the brakes and expect the car to stop in a straight line. But a normal braking procedure wouldn't notice much difference.
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Old 30th March 2011, 09:54   #69
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Default Re: What to do in case of Brake Fail !!

Here is a related question : Have any of you been in the unfortunate situation where you car's brakes failed? If so, what did you do about it?

My Padmini's brakes failed one fine afternoon, when driving home from a lunch party. Luckily, I was two blocks away from home and in a bylane (thus, at a very low speed). Approaching the junction with no brakes was a scary experience nevertheless . Standard response : Heavy engine braking. I still couldn't stop before the junction, but luckily there wasn't any car going perpendicular to me.

Another time, my Jeep's front disc brakes gave up after an offroad stint damaged the brake plumbing (all the brake fluid leaked out). This wasn't as bad as I still had the rear drum brakes. Drove extra conservatively and reached home safe. S-BHPian Aditya will remember the experience.
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Old 30th March 2011, 13:11   #70
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Default Re: What to do in case of Brake Fail !!

I had experienced brake failure once. But the car was parked in the garage. As I pressed the brake pedal before starting it, I noticed the pedal went in all the way. So I tried pumping it a few times, to no avail. Finally called a mechanic. He inspected it and decided to drive it to the workshop. I cautioned him, but he said once the engine starts, some braking power will be restored. So I drove with him to the workshop and although the braking power was much less, I could slow down the vehicle by standing on the pedal, so to speak. He then fixed the leakage, bled the lines and topped up the fluid and that was that.
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Old 30th March 2011, 16:10   #71
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Default Re: What to do in case of Brake Fail !!

I have experienced brake failure a long time in an Ambassidor.I brought the vehicle to a halt by downshifting to the third gear (steering column mounted shift) which promptly slipped which was a common happening with these cars and then brought the vehicle to a halt by shifting to second causing the gearbox to groan and moan and by scraping the kerb. We could do so without much damage to the other roadusers and pedastrians in those days as the traffic was not as heavy as it is these days.
No doubt today's vehicles are much more reliable than the Ambys of yore! All the points stated in this thead are of vital importance. The most important point is 'not to panic!' I think that this can be done by simulating brake failure (By not using the brakes!) in an empty ground and putting into practice all the points mentioned in this thread. This will give one a 'feel' for brake failure and help to handle it better.
Regards,
Ashok
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Old 31st March 2011, 18:10   #72
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Default Re: What to do in case of Brake Fail !!

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Originally Posted by jigbarai View Post
^^
yes - but at the cost of transmission damage.
Not the case in modern ATs. The transmission will only downshift when the engine speed or vehicle speed are safe enough (both for the systems and the car in general). The transmission controller wouldn't allow the shift to happen if the conditions are not right.
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Old 31st March 2011, 18:17   #73
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Default Re: What to do in case of Brake Fail !!

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Originally Posted by nukeblitz View Post
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.
Even in cars with rear discs, the parking brake/handbrake is invariably made of add-on drums to the rear discs. The use of rear discs for the park brake is still only found in relatively higher end cars.

Moreover, the limiting factor while braking with only your rear wheels (read handbrake) is generally the wheel skid rather than the brake proving insufficient. So in any case, regardless of the type of brake used in the rear wheels, always pull the lever slowly rather than all of a sudden.
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