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    Slam on Brakes - What Does Cop See?

    More highway adventures. :

    Clean and green and straight, got 'er up to a nice 90 mph.

    All of a sudden there's a cop coming in opposite direction.

    I slam on brakes.

    I had car in PASM (stiff) mode.

    Brakes "lock" (maximum ABS) and there's even some rubber skid sound.

    I'm on the brakes HARD and then _off_ brakes really fast; just to get speed "instantly" down.

    My question:

    What did the cop see? How much of a dip of the front bumper was evident with PASM on? Does screeching rubber mean a puff of white smoke?

    He was far enough away that I saw him first and I _believe_ he would have had to be looking right at me to see it.

    Would slamming on brakes create an event which would catch people's eyes?

    The cop kept going as I starting wondering where my license and registration were. YIKES!!!


    Re: Slam on Brakes - What Does Cop See?

    You'll be fine! I was driving an old BMW M5 for a dealership for first time and I had

    a) no idea that a cross roads was approaching
    b) that the car had no working ABS...


    Must have been an odd sight to see a car skid right across the junction wheels smoking and fully locked and then just drive off normally once across!

    My guess it with the PASM on you prolly could hardly see a thing..it feels like the car is "dipping" more than it looks like it is...be carefull nextime!

    Re: Slam on Brakes - What Does Cop See?

    I don't think they'll see anything appreciable during the day, however headlighs dipping ever so slightly may give you away at night. Just be sure you're off the bake as he passes by so the brake lights don't attract his attention. Close one, Bra'h! !

    Re: Slam on Brakes - What Does Cop See?

    What difference does it make if they saw something? As long as they didn't get a reeding of you doing 90, right?

    BTW, if you're slamming on the brakes with working ABS you don't get any white smoke.

    Re: Slam on Brakes - What Does Cop See?

    Quote:
    JohnJohn said:
    What difference does it make if they saw something? As long as they didn't get a reeding of you doing 90, right?

    BTW, if you're slamming on the brakes with working ABS you don't get any white smoke.



    The cops can do anything they want if they see something indicating "trouble." I could have been drunk, or having a heart attack, or holding a hostage at gunpoint, in any case jerking the car like that can make a nosy cop, or a mad dog pounce.

    Who wants to get stopped? All the cars I "wrecklessly" passed on that highway for the last hour would drive by cheering!


    Re: Slam on Brakes - What Does Cop See?

    You got a point there...

    Re: Slam on Brakes - What Does Cop See?

    Quote:
    MMD said:
    Quote:
    JohnJohn said:
    What difference does it make if they saw something? As long as they didn't get a reeding of you doing 90, right?

    BTW, if you're slamming on the brakes with working ABS you don't get any white smoke.



    The cops can do anything they want if they see something indicating "trouble." I could have been drunk, or having a heart attack, or holding a hostage at gunpoint, in any case jerking the car like that can make a nosy cop, or a mad dog pounce.

    Who wants to get stopped? All the cars I "wrecklessly" passed on that highway for the last hour would drive by cheering!





    Yes, the bozos can use any excuse to stop you. If they noticed the "dip" in the nose or saw smoke from the tires they could likely use that as "probably cause" to stop you. In Virginia, the state police often use the forward looking radar/lidar and that "keeps my on my toes" when I take a chance and speed.

    They're bozos on a revenue hunt!!!

    Jim

    Re: Slam on Brakes - What Does Cop See?

    Quote:
    Jim48 said:


    Yes, the bozos can use any excuse to stop you. If they noticed the "dip" in the nose or saw smoke from the tires they could likely use that as "probably cause" to stop you. In Virginia, the state police often use the forward looking radar/lidar and that "keeps my on my toes" when I take a chance and speed.

    They're bozos on a revenue hunt!!!

    Jim



    Yeah, funny that I "hate" cops only on the highway.

    Otherwise: I'm really happy to have them around and I respect the work they do.

    I wonder how many accidents are caused by Porsches and "excessive speed" compared to other cars and "excessive speed?"

    Okay..., ahem..., okay..., I wonder how many accidents are caused by Porsches and "excessive speed" _with drivers over 40 yo_ compared to other cars and "excessive speed."


    Re: Slam on Brakes - What Does Cop See?

    Quote:
    MMD said:
    More highway adventures. :

    Clean and green and straight, got 'er up to a nice 90 mph.

    All of a sudden there's a cop coming in opposite direction.

    I slam on brakes.

    I had car in PASM (stiff) mode.

    Brakes "lock" (maximum ABS) and there's even some rubber skid sound.

    I'm on the brakes HARD and then _off_ brakes really fast; just to get speed "instantly" down.

    My question:

    What did the cop see? How much of a dip of the front bumper was evident with PASM on? Does screeching rubber mean a puff of white smoke?

    He was far enough away that I saw him first and I _believe_ he would have had to be looking right at me to see it.

    Would slamming on brakes create an event which would catch people's eyes?

    The cop kept going as I starting wondering where my license and registration were. YIKES!!!






    Only the cop knows the answer to these questions. If you saw the cop what makes you think he didn't see you?

    Re: Slam on Brakes - What Does Cop See?

    Quote:
    MMD said:
    Quote:
    JohnJohn said:
    What difference does it make if they saw something? As long as they didn't get a reeding of you doing 90, right?

    BTW, if you're slamming on the brakes with working ABS you don't get any white smoke.



    The cops can do anything they want if they see something indicating "trouble." I could have been drunk, or having a heart attack, or holding a hostage at gunpoint, in any case jerking the car like that can make a nosy cop, or a mad dog pounce.

    Who wants to get stopped? All the cars I "wrecklessly" passed on that highway for the last hour would drive by cheering!





    I especially hate it when the cars I passed honk and cheer the cop on. Sometimes they stop just to give the cop a pep talk.

    Re: Slam on Brakes - What Does Cop See?

    Headlight dipping is a thing of the past with the Bi-Xenon self-leveling lights. Second, these suspensions are quite stiff, so there is going to be relatively little body movement to give this away.

    Now to the radar systems. They don't just fire a single pulse at you. They fire several, known as the PRF,--pulse repetiiton frequency or recurrance frequency. This is automatic. If the PRF isn't highly sophisticated on these simplistic highway radar guns then you do benefit. What happens internally within all that gadgetry is that the initial radar return will be compared to the next subsequent return. It goes through a logic routine to begin the process of filtering out bogus returns. Let's assume that the first return has you at 85 mph according to the doppler shift of that pulse. Then the next return shows your speed at 60 mph,--the logic circuit will calculate this as a significant delta and possibly just throw the whole thing out, essentially saying that there is no way you can be doing 85 mph one second and 60 mph in the next. It would discount it as clutter or something extraneous. Our cars DO have the deceleration potential to essentially 'break-lock' on many highway radar units. I believe the PRF on laser units are much higher so there is a lesser chance of breaking lock there.

    Thus, it always pays to react QUICKLY whenever you encounter a 'hit.' When he finally does get consistent returns off your vehicle it may be at a more 'legal' velocity. By the time he gets solid returns off your car you can be well below your earlier cruising speed. As police radar units become increasingly sophisticated their PRF is higher and the time difference between the samplings will be lower, and your ability to show a sizable difference between subsequent pulses goes down.

    Dan

    Re: Slam on Brakes - What Does Cop See?

    Thanks Dan.

     
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