[B747]

ABS works by regulating the pressure in the hydraulic lines so it doest matter whether it is drum or disk brakes.

Originally Posted by Rtech

The Swift and the Hyundai Getz have BAS which works on their front wheels only.

Are you sure about this ? because if you open the bonnet of swift you can see the ABS unit on the right side corner of the car(driver side)
it has two pipe lines as input from the brake pedal/booster and 4 pipes as output to all the 4 wheels. If it is a two channel ABS why is it connected to all the four wheels, moreover if you remove the wheels (any of the 4) and look behind the wheel hub you can see electrical connection which is actually the wheel speed sensor, again why it connected to all 4 wheels if it is a 2 channel ABS.
As per my knowledge swift has 4 channel ABS.

[Kinetik]

Originally Posted by adya33

Could you please explain your statement. Because on drum breaks the quick release and hold mechanism won't work which is basic principle of ABS.

Hi adya, the abs module just simulates a human pumping the brake pedals (quick release and hold) , of course ABS does this at a high frequency and subjective to conditions at each wheel, why do you think quick release and hold function wont work on a drum brake ?

Besides if it were only the front wheels which are ABS equipped, consider your car goes over a patch of Oil etc and looses traction on all four wheels the front wheels which have ABS would be more effective i.e would cover less distance to stop while the rear wheels would simply lock, resulting in more braking distance , wouldn't that imbalance the car ? , it would be better off if there was no ABS, atleast the braking distance would be approximately same on all the wheels.

[karthik247]

Its not just the Swift, Accent etc... The Skoda L&K also has only a 2ch. ABS then...

BTW, doesn't the ABS increase stopping distance??

[Kinetik]

Originally Posted by karthik247

Its not just the Swift, Accent etc... The Skoda L&K also has only a 2ch. ABS then...

BTW, doesn't the ABS increase stopping distance??

2 channel means that 2 wheels being controlled per channel , a channel is line of brake pressure.

So the 2 wheels which are being controlled by 1 channel could be on one axle or could be criss-cross.

the best is 4 channel, where all 4 wheels are independantly controlled,

On most surfaces abs reduces stopping distancee, more important is the vehicle is steerable, only under very few conditions does ABS increse stopping distance, like snow, gravel , where locking of the wheels is required to move the layer of snow/gravel between the tyre and road and enable the tyre to reach the road surface.

[Rtech]

Originally Posted by B747

Are you sure about this ? because if you open the bonnet of swift you can see the ABS unit on the right side corner of the car(driver side)......
As per my knowledge swift has 4 channel ABS.

Hmm. I'm very sure about the Getz. The Swift bit was told to me by someone from Maruti itself. But, I haven't checked up on that so maybe it wasn't correct information.

What does the technical data say?

[abhibh]

Originally Posted by Kinetik

2 channel means that 2 wheels being controlled per channel , a channel is line of brake pressure.

So the 2 wheels which are being controlled by 1 channel could be on one axle or could be criss-cross.

the best is 4 channel, where all 4 wheels are independantly controlled,

On most surfaces abs reduces stopping distancee, more important is the vehicle is steerable, only under very few conditions does ABS increse stopping distance, like snow, gravel , where locking of the wheels is required to move the layer of snow/gravel between the tyre and road and enable the tyre to reach the road surface.

Kinetik is right i just dug out somemore info on ABS and the 3 channel ABS works just like 2 channel.

In 3 channel the front 2 wheels are controlled by 2 independent channel and rear are controlled by 1 channel. Same can be in the case of Swift but one channel for front and one for rear.

[adya33]

why do you think quick release and hold function wont work on a drum brake ?

As a technical exercise ABS can be fitted on drum breaks but its won't be half as effective as disk breaks.

Besides if it were only the front wheels which are ABS equipped, consider your car goes over a patch of Oil etc and looses traction on all four wheels the front wheels which have ABS would be more effective i.e would cover less distance to stop while the rear wheels would simply lock, resulting in more braking distance , wouldn't that imbalance the car ?

On normal cars with front disc and rear drum setup the breaking efficiency of front wheels is better than rear wheels. So with only front ABS there won't be problem of imbalance as rear breaks breaking effectively will not be as strong as front breaks.

[Kinetik]

hi adya

Originally Posted by adya33

As a technical exercise ABS can be fitted on drum breaks but its won't be half as effective as disk breaks.

I fully agree with your comment about drum brakes not being as efficient as discs, but maybe the amount of effect that they do produce is enough for that vehicles specifications, we dont need a four pot caliper on a Lawnmower do we ? . afterall manufacturers do their R&D.

Originally Posted by adya33

On normal cars with front disc and rear drum setup the breaking efficiency of front wheels is better than rear wheels. So with only front ABS there won't be problem of imbalance as rear breaks breaking effectively will not be as strong as front breaks.

this fine balance of brake bias, coefficient of friction ( static & kinetic ) of the tyres with road suface & brake pads with discs would hold true for a new vehicle, how would you control this after brake wear and tyre wear, obviously the wear paterns on all the components on the front axle and rear axle will not be in the same ratio, wouldn't that upset the fine setup? .

Besides I have not come across nor have read any currently manufactured automobile having only front wheels ABS controlled, it would be intresting to know how they do it.

[suman]

Just to add on from first hand ownership experience & research done when I was zeroing in on which "beast" to buy -

Ford Endeavour - Front ventilated discs, Rear self adjusting drums, ABS on all 4 wheels.

Ford Fiesta 1.6 SXI - Same as above, ABS on all 4 wheels.

So I don't agree with the theory that ABS is not possible on drums. As far as effectiveness is concerned, I've not felt anything remotely ineffective on occasions where my Fiesta's ABS has come into play.

Cheers

[suman]

Sorry for the extra post (the time limit for editing had expired) but how could I forget -

Safari Dicor VX 4x4 - Front Ventilated discs, Rear drums, ABS on all 4 wheels

[khoj]

Conclusions
1. ABS is not dependent on type of braking mechanism i.e Disc or Drum.
2. ABS system incorporates all 4 wheels.
3. An ABS equipped vehicle will be safer to steer and stop during a comparative braking situation versus a non ABS equipped vehicle.

For further real world experience on whether to buy ABS equipped or otherwise read the following thread:
http://www.team-bhp.com/forum/techni...g-zxi-abs.html

[Zappo]

What are you bothered about? On whether to opt for ABS in your next car? If so let me tell you the answer should be a resounding yes. Anyone who does some moderate speeds and foresees a situation anytime where he or she may need to slam on the brakes in a hurry can do with the assistance of ABS.

If your query is on whether the ABS can be available on all 4 wheels even though the rear brakes are drum types the answer is yet again yes. The ABS is a simple solution that does not really depends on the type of brakes. It works on a sensor that lets the CU know whether the wheels are getting locked and based on that the pressure on the brake lines are released and then again applied. This happens many times in a second in an ABS assist, thus preventing the wheels from getting locked. And it can very well be applied to drum brakes and indeed applied as well. Most vehicles that I am aware of have ABS on all 4 wheels. Now whether they are all independent (4-channel) or have an independent front with a single channel rear (3-channel ABS) is something you will need to find out on a case to case basis.