Which will be a fat lot of good, come the day that you need to be able to stop very quickly, but
as a responsible motorist, that is your decision.
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prefer to prolong the life of my tyres!>>
As ABS prevents the wheels locking up (we were taught cadence braking in my time), the effect on tyres is far, far less as the vehicle doesn't skid.
One of the key points about ABS is that it allows a driver to maintain control of the vehicle and steer it, if necessary, during braking.
To be honest, I can only recall one occasion when I've actually activated the ABS.
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I do give my brakes a severe testing now and again, several hard stops one after another on a very quiet stretch of road.
They always seem better for this...after they've stopped smoking..;)
Good point too about knowing how your car feels at the extreme's, and if there's something that isn't quite as it should be you find out before that horrible moment of the real panic stop.
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A good idea, everyone should have an idea what their car would do in extremis. Good for those lightly used rear brakes too, keeps them clean and moving.
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As I have superb anticipation :-) I am a light brake user. I also find that a few hard applications occaisonally does improve the feel, and initial bite of the brakes.
Edited by Old Navy on 22/08/2009 at 10:59
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I tried it on my current car, warm, dry day, road clear.
I hit the seat belt so hard it hurt!
I won't be doing it again unnecessarily.
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Funny thing about modern cars is that good drivers with anticipation and observation are bad for the rear brakes as they are used little.
The driver who goes everywhere at full throttle and stamps on the brakes at the last minute are often better for the brakes.
It annoys me that better drivers have more rear brake problems.
It is essential that all motorists know what their car is like. I'd go as far as saying everyone should practise a quick lane change (as if avoiding a side swipe). But only practise in the dry on a deserted road.
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I didn't think ABS reduced the braking distance - or have I, as seems to be common with ABS, misunderstood how it works?
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I think ABS only reduces stopping distance in that it stops wheel lock up in an emergency stop.
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The most reliable test is to have an elderly lady pull out of a side road, turning right as you approach her whilst completely invisible in a bright red car in broad daylight just 20 metres away. I just love Michelin tyres and my Mazda 323's ABS..........
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I test my ABS on wet cobbles, trouble is it rarely rains in Edinburgh.
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Though I think the OP has a point, I have found that on the rare occasion that I have had to brake hard I haven't had time to think about it and just stamped on them and it was fine. Have to admit though that it has always been low speed stuff ie 30 mph or so.
To brake really hard from 60 mph or higher would be a different proposition I should think and worth experiencing in a practise situation before you have to rely on it!
Just mt thoughts.
FF
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If I understand the mechanics of braking correctly, maximum braking efficiency occurs just before the point that the wheels lock up, so the ability of ABS to allow you to brake very hard without locking up the wheels means that a driver should, if he presses the pedal hard enough, achieve the best braking possible.
Of course there are other factors, including reaction times, tyre condition, weather etc.
It also helps if the driver is paying attention to his surroundings.
Edited by Mr.Tee43 on 22/08/2009 at 12:59
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>>If I understand the mechanics of braking correctly, maximum braking efficiency occurs just before the point that the wheels lock up
Under dry conditions it's at about 20% slip.
The ABS controller does not know how fast the car is travelling during a braking event; all the tyres will be slipping to different extents, so, counting how fast wheels rotate is no good!
So, the controller looks at how quickly a wheel decelerates, and if the wheel decelerates quicker than a given threshold value, the brake pressure is reduced temporarily, and then, allowed to build again. This cycle repeating much quicker than a human being could follow.
The effect of this ABS cycling is that the tyre goes from slipping below 20% to beyond 20% and back again rapidly, giving a better average control, i.e., staying closer to the slip value which gives best braking than by far the majority of drivers ever could. As gross slippage, i.e., 100% slip is avoided, steering control is also maintained, which, if anything is the prime objective of the ABS.
Stamp as hard as you can on the pedal, steer if you need to, let the computer control the brakes!
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I had always understood that ABS did not actually reduce stopping distance, it maintained control/steering.
Is that understanding wrong then?
FTF
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It reduces stopping distances in that skidding is avoided.
The braking system's efficiency is the same with or without ABS, but no driver using cadence braking can match an ABS system.
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The braking system's efficiency is the same with or without ABS but no driver using cadence braking can match an ABS system.
I would have to disagree there.
There are a FEW drivers out there that can out cadence brake ABS.
I am really talking about top notch racing drivers of course.
One other point about ABS, which I have experience of 1st hand, is that it can get confused.
a few years ago I was on the M25, in heavy rain, when the vehicles in front lit up like Xmas trees.
I stood on the brakes, only for the wheels to lock. the car had started to aquaplane (6 mm on tyres)
I did manage to stop, but the ABS had been pretty useless in that case. (I did get the system checked - no faults found)
with all 4 wheels on water (or ice) the ABS will think the car is stationary, if all wheels stop turning. the human brain will of course realise the car itself is still moving.
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>>There are a FEW drivers out there that can out cadence brake ABS.<<
yes, I would agree. Many bikers believe that ABS reduces the braking effectiveness - however, your 2nd point applies - it's only the full time bike testers and racers who can outbrake the ABS system. Most bikers are much better off with ABS.
Bikers especially need to be able to handle emergency braking.
I also agree with the OP - it's a very good idea to test your brakes fully. I've posted here before about my MGF, which could not manage an emergency stop on some occasions - I found this out on an airfield day. I would guess that there are a significant number of cars that could not perform an emergency stop properly.
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with all 4 wheels on water (or ice) the ABS will think the car is stationary, if all wheels stop turning. the human brain will of course realise the car itself is still moving. <<
With all 4 wheels aquaplaning you dont want your brakes trying to activate - you'll aquaplane further.
On slippy ice, ABS can sometime be less effective than allowing wheels to skid. I think newer systems can take this into account but I don't know the technical method behind it.
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With all 4 wheels aquaplaning you dont want your brakes trying to activate - you'll aquaplane further.
Exactly.
reread my post, that is what I said.
I dislike all the electronic 'aids' that are fitted to cars today, NOT of course because they make cars safer, BUT the opposite.... the fact that they make cars MORE dangerous - BECAUSE the people driving THINK the aids will get them out of ALL troubles....
ABS is fantastic - but at times will fail to work - ice being the big one.
traction control - sensible use of the loud pedal always used to work ok.
pre crash sensing - isnt that what eyes, ears, and brains are for?
The thing is, some cars would be undrivable without the aids.
and IMHO too many cars that anyone can drive come under that umbrella - AMG 63's for one
M3's for another - disable the TC etc, and Im sure the car work just be uncontrollable.
Edited by the swiss tony on 22/08/2009 at 17:41
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>>I would have to disagree there.>>
I was referring to ordinary motorists like you and me...:-)
I seem to remember something about ABS sometimes not being as good on snow than the snow building up in front of the tyres and thus slowing the vehicle down.
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Stamp as hard as you can on the pedal steer if you need to let the computer control the brakes!
My car also has a system called brake assist. And boy does it assist you in braking when you stamp on the pedal. The computer takes over and puts the brakes on even harder and pulses the brake lights on and off for good measure. This is supposed to warn people behind you, but I suspect 99% of those people will just think that I've got faulty bulbs as they crash into the back of me.
Edited by Dynamic Dave on 22/08/2009 at 17:00
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As ABS prevents the wheels locking up ..........
It actually makes them lock rhythmically, on and off. Try it on a smooth dry road and then look at the dotted lines of rubber you've made on the road surface.
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>>It actually makes them lock rhythmically, on and off.
No, the wheels don't actually lock - they shouldn't get anywhere near 100% slip (or 100% lock depending upon how you view it!) The fact that rubber is laid simply means the tyre is doing significant work, with some measure of sllip.
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No the wheels don't actually lock - they shouldn't get anywhere near 100% slip (or 100% lock depending upon how you view it!) The fact that rubber is laid simply means the tyre is doing significant work with some measure of slip.
That's what I meant, but I'm not as eloquent as you!
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