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Old 14th April 2011, 15:35   #16
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Default Re: Reducing ABS sensitivity - SX4

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Get better tires. (better meaning softer and more grippy compund/thread) upsize if necessary
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Most likely they are JK's which we know are not that great.
The tyres are 205/16 Continental CPC2 which are pretty grippy


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Normally, you should brake/ slow down before the potholes than when into them. ABS will always kick in (and should) when the wheels lock and they'll lock if the tires are in the air. Try going over pot holes at a little less speed so the car does not bounce much.
Let me try rephrase the question better
Most of the time, I brake well ahead in time.. Also, am a fairly experienced driver and have been manually able to modulate brakes on my old workshorse Opel Corsa...
Yet the reason I was still extremely keen on ABS on my next car was coz in panic situations, it may not always be possible to think straight and slam on the brakes as a reflex action

However, there are occasions when I have felt that the ABS kicks in unnecessarily, esp at low speeds..
e.g when trying to brake on a gravel filled road, when normal braking would cause the wheels to dig into the gravel and bring the vehicle to stop in time.. But with ABS, the initial slippage on gravel would cause the ABS to activate and actually increase the stopping distance considerably (which could mean the difference between a hit and a save in bumper-to-bumper traffic)

Now in this particular scenario , I was driving at slow speeds with a small pothole coming up which would not really necessitate braking
until someone with a deathwish or on a suicide quest decided to dash across the road perfectly perpendicular to the traffic direction barely 5 mtrs away from me
Now in case of a non ABS setup, I'd have hit the brakes gently and come to a standstill well in time.
However, since 1 of the wheels was momentarily in the air, the ABS got activated and for the next 1 odd second, there was zero braking action ..

Hence my question
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Old 14th April 2011, 16:31   #17
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Default Re: Reducing ABS sensitivity - SX4

I think you are bringing up two different problems here. The original one is around your pothole issue where 1 tyre is up in the air. In that scenario i believe EBD (electronic brake distribution) should come into play and would still give you best possible braking on the other 3 tyres in contact with surface rather than completely stopping brake force on all 4 wheels. I am not certain but maruti does provide ABS with EBD or all manf pretty much do.

Regarding the second case of braking distance between ABS vs non ABS, I am not a ABS expert but i think technically in certain scenarios it might be possible to have longer braking distance with ABS, for eg in your case gravel where skidding tyres might dig in and find better surface vs with ABS when wheels dont skid. Experts your thoughts around this one?
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Old 14th April 2011, 20:39   #18
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Default Re: Reducing ABS sensitivity - SX4

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Originally Posted by abhi182 View Post
However, there are occasions when I have felt that the ABS kicks in unnecessarily, esp at low speeds..
e.g when trying to brake on a gravel filled road, when normal braking would cause the wheels to dig into the gravel and bring the vehicle to stop in time.. But with ABS, the initial slippage on gravel would cause the ABS to activate and actually increase the stopping distance considerably (which could mean the difference between a hit and a save in bumper-to-bumper traffic)

That ABS increases stopping distances on loose surfaces (gravel, snow, sand) is well known and well documented.
....
However, since 1 of the wheels was momentarily in the air, the ABS got activated and for the next 1 odd second, there was zero braking action ..
Hi,
This is very unusual and intriguing. Have you faced this phenomenon more than once? Is it replicable?

Regards
Sutripta
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Old 15th April 2011, 11:41   #19
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Default Re: Reducing ABS sensitivity - SX4

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Originally Posted by abhi182 View Post
... e.g when trying to brake on a gravel filled road, when normal braking would cause the wheels to dig into the gravel and bring the vehicle to stop in time. But with ABS, the initial slippage on gravel would cause the ABS to activate and actually increase the stopping distance considerably (which could mean the difference between a hit and a save in bumper-to-bumper traffic)..
IMHO you are being prejudiced here and empirically doing an inequal comparison. In the same situation if ABS would kick-in (tyre locking, and vehicle slipping on gravel), ABS stops the vehicle in a shorter distance by minimizing or preventing slipping / skidding.

Not sure what you mean by 'digging into gravel' (since gravel behaves like a liquid in this scenario) but without ABS, the slipping / skidding cannot be controlled and will result in a longer braking distance, that too without steering control.

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Originally Posted by abhi182 View Post
... Now in this particular scenario, ... someone with a deathwish or on a suicide quest decided to dash across the road perfectly perpendicular to the traffic direction barely 5 mtrs away from me
... 1 of the wheels was momentarily in the air, the ABS got activated and for the next 1 odd second, there was zero braking action .. ...
Zero braking action? Sure, that wheel can't brake the vehicle if it is in the air! The other wheels on the ground definitely will. But, are you understanding the ABS action correctly?

* ABS senses conditions ~20 times a second
* ABS valve pulsing takes place ~10-30 times a second depending on speed of vehicle (less pulsing at lower speed)
* If the wheel was in the air 'momentarily' (~100ms at 30kmph over a 0.3m/1' pothole) and ABS thought that wheel locked, it would have pulsed only that wheel for a very short while before realizing that the same wheel is not locked when it makes contact with the ground. The wheel does not remain perpetually in air and after 100ms will make contact with the road again (rather rudely on the trailing edge of the pothole ) and start rolling once again
* The 'braking distance increase' for this one wheel incident would have been 1' or less at 30kmph - is it that significant deserving condemnation? And I am not even talking of 'bumper-to-bumper traffic' that you mentioned, = <5kmph.
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Old 15th April 2011, 13:53   #20
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Default Re: Reducing ABS sensitivity - SX4

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Originally Posted by abhi182 View Post
However, since 1 of the wheels was momentarily in the air, the ABS got activated and for the next 1 odd second, there was zero braking action ..
Doesn'tSX4 have EBD?. If so, doesn't EBD supposed to take care of this?.

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Originally Posted by Sutripta View Post
Hi,
This is very unusual and intriguing. Have you faced this phenomenon more than once? Is it replicable?
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Originally Posted by DerAlte View Post
... ABS stops the vehicle in a shorter distance by minimizing or preventing slipping / skidding.
Hey guys, I think the OP is referring to this. abhi182 please confirm!.
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Old 19th July 2013, 11:17   #21
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Default ABS does not "kick in"

My situation is absolutely other way round, as stated in the thread. Couple of days back i was driving my Sx4 Zdi and had to apply emergency brakes @ speed of 40km/hr. Surprisingly i did not feel any judder on Brake pedal and behind me there were long tyre marks on road.

I presume that ABS didn't actually kick in. There is no ABS check light glowing ones the car has actually started (during ignition mode yes ABS indicator does glow)

Members pls advice!
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Old 19th July 2013, 11:41   #22
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Default Re: ABS does not "kick in"

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Originally Posted by amitpunjani View Post
My situation is absolutely other way round, as stated in the thread. Couple of days back i was driving my Sx4 Zdi and had to apply emergency brakes @ speed of 40km/hr. Surprisingly i did not feel any judder on Brake pedal and behind me there were long tyre marks on road.

I presume that ABS didn't actually kick in. There is no ABS check light glowing ones the car has actually started (during ignition mode yes ABS indicator does glow)

Members pls advice!
Find a sandy track somewhere, away from traffic & test the ABS by applying brakes. Be prepared for a longer braking distance, as if ABS is working, the wheels would not lock even on the sandy road.
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Old 30th July 2013, 02:04   #23
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Default Re: Reducing ABS sensitivity - SX4

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Originally Posted by DerAlte View Post

Not sure what you mean by 'digging into gravel' (since gravel behaves like a liquid in this scenario) but without ABS, the slipping / skidding cannot be controlled and will result in a longer braking distance, that too without steering control.
Audis used to have a switch to turn-off the ABS when it would 'fail', such as in snow and on gravel. Then they realised most people wouldn't appreciate such a switch and they were placing themselves wide open for legal action, especially in the USA where appreciation of such automotive subtleties seems to be low, and their ability to sue foreign companies is very high!

When Range-Rover first developed their ABS system, they made it so that it cut in later than for other vehicles - ie when the wheel had slowed a little more. This suited the vehicle's purpose and I having experienced it I can vouch for its efficacy. I'm not entirely sure of this, but my Mercedes 124s seem to have an ABS system which cuts in later than on other cars too.

Rally teams tune their ABS to suit local conditions.
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