Panic stop- lots of smoke from tires
10-14-2003, 04:24 PM
#1
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Panic stop- lots of smoke from tires
I had to do a panic stop yesterday on the highway- going about 70mph, everyone slammed on the brakes due to an accident that just occured on the other side of the highway (I guess lots of people were "rubber-necking"). Anyway, a quick question for those more knowledgable or maybe people that track their cars- when you press the brakes as hard as you can in a panic stop, do the wheels lock up even though the car has ABS? I have a 1993 964, and didn't really feel pulsations of ABS like I do with my BMW, and wouldn't have expected that much smoke to come pouring out from the tires. Luckily I was able to stop in time, and the guy behind me was able to stop and not rear-end me. The car stopped very nicely, and was dead-straight. I had the convertible top down- besides the panicked stop, it was pretty cool I must admit, and would have made a nice picture with all that smoke swerling around the car 
10-14-2003, 04:44 PM
#3
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Hi Andrew,
When my ABS kicks in I feel it the pulsations thru my foot. Only when I'm autocrossing and making a turn does the inside wheel 'chirp" when braking to the point when the ABS kicks in ( this is when I get my slowest times, BTW). On a straight stretch, I don't smoke my tires as the ABS won't allow that.
I agree with John, something isn't right here.
You know from your BMW the feeling you get when ABS kicks in? The physics is the same and you should get the same feeling thru your foot, though maybe more subtle.
Test it out on a slick road, but in a controlled situation, ie. not a school zone!
mojo
When my ABS kicks in I feel it the pulsations thru my foot. Only when I'm autocrossing and making a turn does the inside wheel 'chirp" when braking to the point when the ABS kicks in ( this is when I get my slowest times, BTW). On a straight stretch, I don't smoke my tires as the ABS won't allow that.
I agree with John, something isn't right here.
You know from your BMW the feeling you get when ABS kicks in? The physics is the same and you should get the same feeling thru your foot, though maybe more subtle.
Test it out on a slick road, but in a controlled situation, ie. not a school zone!
mojo
10-14-2003, 04:51 PM
#4
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Try again on a very wet or even icy road, and see what the ABS does. If you start to spin with locked brakes, your ABS is non-functional.
It would not worry me to much if the ABS died on my car. I miss my non-ABS cars. There is no doubt that you can panic-stop faster without ABS, provided you have the presence of mind to modulate the pedal as you start to skid. With ABS, you should press the brake pedal as hard as you can, and let the ABS system worry about skidding. It sounds like you did your emergency stop exactly correct - congratulations on the favorable outcome.
It would not worry me to much if the ABS died on my car. I miss my non-ABS cars. There is no doubt that you can panic-stop faster without ABS, provided you have the presence of mind to modulate the pedal as you start to skid. With ABS, you should press the brake pedal as hard as you can, and let the ABS system worry about skidding. It sounds like you did your emergency stop exactly correct - congratulations on the favorable outcome.
10-14-2003, 06:16 PM
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It's a real problem when you drive cars with and without ABS - trying to use the correct technique for each, in extremis. Not that I make a habit of this! 
When I had my Elise (I had my 964 also), the non-assisted/non-ABS brakes were simply superb, but I never quite trusted myself to do the right thing in an emergency, having got so used to ABS. It just took that extra second or two to start to modulate it - maybe a second or two too long.
On balance, I wouldn't go back.
Maybe I'm just getting too old to cope with too many different factors. (I tried to find a sixth gear on the Elise more than once - unfortunate as it was the 'reverse' slot!)
When I had my Elise (I had my 964 also), the non-assisted/non-ABS brakes were simply superb, but I never quite trusted myself to do the right thing in an emergency, having got so used to ABS. It just took that extra second or two to start to modulate it - maybe a second or two too long.
On balance, I wouldn't go back.
Maybe I'm just getting too old to cope with too many different factors. (I tried to find a sixth gear on the Elise more than once - unfortunate as it was the 'reverse' slot!)
10-14-2003, 10:56 PM
#6
Three Wheelin'
Thread Starter
John- ouch on the mistake of reverse for 6th- I'm sure you didn't let the clutch out- ha!
I will say this- the braking in the 911 is super- I remember my 1978, then 1987 and now this 1993 having brakes that can make your eyeballs fall out- a combo of taunt suspension (no nose dive), great brakes, and rear weight bias really keeps these cars planted. That said, I found it quite odd, but I don't remember feeling the ABS pulsations. It could be that I was concentrating more on the situation, but then again the car really was so well controlled, that I had time to notice the smoke swearling around me and to peek in the rear view at the car close to me behind as the split second or two went in what seemed like slow motion. I'll have to check it out further on ice or wet road...although the car is rarely out in those conditions
Maybe the ABS works, but still allows some wheel lock-up? I have to test it out...I know my dad's 1985 528e has ABS that is non-functional, so maybe these things break after a number of years?
I will say this- the braking in the 911 is super- I remember my 1978, then 1987 and now this 1993 having brakes that can make your eyeballs fall out- a combo of taunt suspension (no nose dive), great brakes, and rear weight bias really keeps these cars planted. That said, I found it quite odd, but I don't remember feeling the ABS pulsations. It could be that I was concentrating more on the situation, but then again the car really was so well controlled, that I had time to notice the smoke swearling around me and to peek in the rear view at the car close to me behind as the split second or two went in what seemed like slow motion. I'll have to check it out further on ice or wet road...although the car is rarely out in those conditions
Maybe the ABS works, but still allows some wheel lock-up? I have to test it out...I know my dad's 1985 528e has ABS that is non-functional, so maybe these things break after a number of years?
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10-15-2003, 05:51 AM
#8
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Originally posted by John Boggiano
It's a real problem when you drive cars with and without ABS - trying to use the correct technique for each, in extremis. Not that I make a habit of this!
When I had my Elise (I had my 964 also), the non-assisted/non-ABS brakes were simply superb, but I never quite trusted myself to do the right thing in an emergency, having got so used to ABS. It just took that extra second or two to start to modulate it - maybe a second or two too long.
On balance, I wouldn't go back.
Maybe I'm just getting too old to cope with too many different factors. (I tried to find a sixth gear on the Elise more than once - unfortunate as it was the 'reverse' slot!)
It's a real problem when you drive cars with and without ABS - trying to use the correct technique for each, in extremis. Not that I make a habit of this!
When I had my Elise (I had my 964 also), the non-assisted/non-ABS brakes were simply superb, but I never quite trusted myself to do the right thing in an emergency, having got so used to ABS. It just took that extra second or two to start to modulate it - maybe a second or two too long.
On balance, I wouldn't go back.
Maybe I'm just getting too old to cope with too many different factors. (I tried to find a sixth gear on the Elise more than once - unfortunate as it was the 'reverse' slot!)
10-15-2003, 06:09 AM
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No but, funnily enough, I've never tried to wrong-slot it. It's sometimes been in my mind, but has gone by the time my hand reaches for the lever. Fortunately, reverse is well out of the way!
It's the Lupo GTi wot causes it!
It's the Lupo GTi wot causes it!
10-15-2003, 12:23 PM
#10
Three Wheelin'
Thread Starter
Well, now I'm curious. What is odd is if for some reason my ABS isn't working, the ABS light doesn't come on... based on other posts of people that have this light come on for no reason, this really will be odd if my ABS isn't functioning and the light stays off!! Buy I'm getting ahead of myself- I'll have to test the brakes in the wet (no ice yet- still another couple of months before that out by me- hopefully)
)
10-15-2003, 01:52 PM
#12
Am I wrong in saying that if all wheels lock at the same time the ABS will have no effect, as if on ice? Unlikley but possible?
Test it by putting two wheels grass/gravel and the other two are on tarmac while braking if the ABS does not kick in it's not working.
Richard 1990 C2
Test it by putting two wheels grass/gravel and the other two are on tarmac while braking if the ABS does not kick in it's not working.
Richard 1990 C2
10-15-2003, 02:47 PM
#13
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The ABS will only work if it detects locking up within a certain load limit (20-40%). This load limit is based on calculated wheel de-celeration. If you exceed this limit on ALL four wheels the ABS will not kick in. This is a safety issue. If the brake pressure is released from all four wheels at the same time guess what is going to happen?
The ABS will also only work when detected wheel speed reaches 10 kph or less. Whether it works or not depends on how fast you get the wheels to this speed. We are talking wheel speed and not driving speed.
Ciao,
Adrian
964C4
The ABS will also only work when detected wheel speed reaches 10 kph or less. Whether it works or not depends on how fast you get the wheels to this speed. We are talking wheel speed and not driving speed.
Ciao,
Adrian
964C4
10-16-2003, 02:03 PM
#14
I had a very similar experience. My top was down and speed was about 90 mph. Some idiot tried to cut in front of me and lost control of his "rice rocket" and spun. My tires, Khumo's on 18" rims, just grabbed the pavement. The P-car was in total control throughout. Also, never felt pulsating from the ABS. Your correct is was "fun".
My ABS light is on when I start the car, and will go out once the car start to roll.
My ABS light is on when I start the car, and will go out once the car start to roll.
10-16-2003, 02:16 PM
#15
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Dear jrb,
This is an indication of a low battery voltage. The ABS light on a C2 should go out the instant the engine starts. The most common cause of this problem is worn alternator brushes and worn slip rings and the output is too low. Follow the checks I have described above to check your alternator output.
Ciao,
Adrian
964C4
This is an indication of a low battery voltage. The ABS light on a C2 should go out the instant the engine starts. The most common cause of this problem is worn alternator brushes and worn slip rings and the output is too low. Follow the checks I have described above to check your alternator output.
Ciao,
Adrian
964C4