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    Dec 7, 2005 8:12:04 PM

    vtach88
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    Hopping front end syndrome....

    I've only driven my first P (997S) for 5 months. I haven't had time to take the PDE courses - but plan to in the spring.
    I've had 2 unusual (for me) experiences with my car:

    1) I took a 110 degree turn onto an empty 3 lane road and tried to gun it (I know.... slow and steady accel is the key)out of the curve and I could feel the rear end driving the front wheels (which were still turned a bit) in a straight line (massive understeer) - and the front end just kind of hopped a few times. It was disconcerting.

    2) Whenever I'm taking an curved overpass that is long, sweeping and at highway speeds - I'm bothered by the hopping/bobbing front end - which sometimes seems to be a bit sideways as well as up/down.

    I know some of #1 was my fault - as I learn about the fat rear wheeled understeering characteristics, but #2 bothers me a bit.

    Am I being too sensitive? Is this terribly unusual - or is my car misbehaving?

    Otherwise, I'm totally pleased with the car....

    Dec 7, 2005 8:50:14 PM

    86BBUB
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    Reply to: vtach88

    Re: Hopping front end syndrome....

    997 front end lightly loaded as most of the mass at rear. Acceleration accentuates this mass differential. Generally 911's simply plow straight ahead until driver lifts off gas (at which point the rear gets loose ). I believe the bobbing is PASM related but I'm not sure.

    Dec 7, 2005 9:00:03 PM

    JJBlade
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    Reply to: 86BBUB

    Re: Hopping front end syndrome....

    PASM definitely accentuates this. My car does not display any of this 'hoppiness' on the -20mm but when I test drove a PASM car it was in evidence.

    Dec 7, 2005 9:05:27 PM

    Turbo 911
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    Reply to: vtach88

    Re: Hopping front end syndrome....

    I hardly notice understeer on 911s, even through enthusiastic driving.

    Dec 7, 2005 9:54:38 PM

    KenH
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    Reply to: Turbo 911

    Re: Hopping front end syndrome....

    The consensus in some magazines seems to be that this is PASM related but I suspect that it is a software side effect that Porsche will "tune out" soon - if they have not done so already.
    The same magazines report that this is not apparent in the Cayman, which may or may not be relevant.

    Dec 7, 2005 11:27:17 PM

    jboyko
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    Reply to: KenH

    Re: Hopping front end syndrome....

    That feeling of the front end hop was always an eye opener. Although nothing bad ever happened, the same front end hop in another vehicle would probably be the signal that you are going to bounce the front end into the tractor trailer that's driving next to you. One of the auto mags had experienced the same wheel hop during some track testing, but they believed that the issue did not cause any loss of control or lowered track times. I agree. It is just one of those things you take on faith, "that every things gonna be all right".

    Cheers,

    jb

    Dec 8, 2005 12:33:31 AM

    KiwiCanuck
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    Reply to: vtach88

    Re: Hopping front end syndrome....

    Interesting ---- I am still learning about the response of the PASM --- which I chose together with 18in wheels, due to the less than ideally smooth roads in the Canadian prairies. A newly sealed road lasts 5-10years as a 160+kphbefore frost heaving etc causes it be less than idael for a Carrera or an NSX.

    The PASM is caught in a dilemma that may not be solvable ---- at lowish speeds (relative to the road undulations that may exist --- that is, a smoothly surfaced road that undulates)the PASM in normal setting gives a nice coseted ride. But cover that same stretch at speed and some of the undulations are firmly damped, others not, as the PASM perceives high accelerations in some cases/or some wheels. This produces a rather unsettled response for the car --- quite odd. The Brits have talked about this on some of their roads. And Pete Stout Editor of 'Excellence', GREAT MAG!, who although a Porsche-lover is unafraid of calling a spade a B--- Shovel, as we Kiwis would say, is quite ambivalent about the PASM and his favorite 997 is the C2 with 'steel' suspension (as do some Brits) ---and wishes that Porsche-NA would offer the 2CS with sports suspension and -10mm lower height to avoid the height change issue.

    ----- in fact under such conditions, the Acura TL (6 spd) with its sports suspension and excellent steering turn-in, is actally faster and more predictable than the C2 Carrera.

    But that is a very unusual piece of road that I am talking about, and the only one that reveals this interesting behaviour. But I drive it every day and so have found it constantly intriguing.

    I do, overall, find the PASM just great ---- no regrets.

    KiwiCanuck

    Dec 8, 2005 12:34:09 AM

    Trundle_GT3
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    Reply to: jboyko

    Re: Hopping front end syndrome....

    PDE will help you understand vehicle dynamics and your car.
    Sign-up ASAP, You will not regret it!!!

    Dec 8, 2005 12:58:04 AM

    vtach88
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    Reply to: Trundle_GT3

    Re: Hopping front end syndrome....

    Quote:
    Trundle997S said:
    PDE will help you understand vehicle dynamics and your car.
    Sign-up ASAP, You will not regret it!!!



    Will do. Understanding the unique handling characteristics will be beneficial.

    However, as others have pointed out above, this undulation issue isn't the driver's fault - and is very unsettling. If it is as easy as "reprogramming" PASM then, I will be first in line. Unfortunately, I suspect it is more complicated. Right?

    Dec 8, 2005 2:40:43 AM

    jboyko
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    Reply to: KiwiCanuck

    Re: Hopping front end syndrome....

    Wow kiwi, you are right on. Also, the Cannabis in Canada must really be taken with limitations.

    jb

    Dec 8, 2005 3:03:43 PM

    john999s
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    Reply to: jboyko

    Re: Hopping front end syndrome....

    The double shuffle on turn in something 911's have had for years. Sometimes it doesn't 'bite' on first turn in and you need to back off and turn in again-quicky! 4wd's don't do it so much at the expsense of steering feel. And PSM gnerally sorts things out when it works out you want to go round the corner not straight on....if you have time you'll see the light come on and feel the inside rear brake to help you out! If you arrive fast and use the weight of the rear engine to help it go a bit neutral it very rarely understeers badly particularly if the front's are loaded as you turn in. I can't see the bobbing nose ever being totally eradicated as you've got a big lump of metal as a cantilever over the rear wheels...

    Dec 8, 2005 5:35:45 PM

    KiwiCanuck
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    Reply to: Trundle_GT3

    Re: Hopping front end syndrome....

    He said:

    "PDE will help you understand vehicle dynamics and your car.
    Sign-up ASAP, You will not regret it!!!

    --------------------
    997S Guards Red "

    Thanks, I think. Are you suggesting that I/we do not understand the dynamics of the car, and that by reading something I have to pay for, I will 'understand' it? While I would like to know WHY my prized 'Carrera' behaves in the fashion, that will not REMEDY the issue! I am not really upset by it --- every car has its idiosyncracies------ it would be nice to know why Porsche did not remedy this behaviour? I have described the issue ----- will understanding why the PASM is not working 100%, and why Rohrl does not even recoginize there is a problem!!---help?

    In my humble, Porsche may be relying too much of Meister Rohrl and the famed Nurbergring (sorry that IS wrong) ---- the Brits get rightly annoyed that German and a few other cars are tuned for the North circuit, while NOT being optimized for other unique countries/roads. E.g. the 997 does NOT like North American 'expansion' joints and broken roads ---- I YEARN for the European roads I see the 997's being driven /tested on. Porsche COULD tune PASM to handle those better ----- but no, Rohrl wins,and 'track day' (if youare NEAR one, wins.

    Now, fellow web-site person, perhaps you would share some of your knowledge, rather than telling us to and find out WHY -----

    Merci


    KiwiCanuck

    Dec 8, 2005 6:16:19 PM

    edz
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    Reply to: jboyko

    Re: Hopping front end syndrome....

    I have not had such experience in my 06 997S, not yet at least. Hopping the front end is generally a sign that you are driving the car to it's limit and if you push harder the car might punish it for it unless you are a very skilled driver. If you redlined the car, it's no surprise. Neverthelss keep in mind the temp of the road surface should be proper along with the tire pressure and whether the tires were warmed up. These are all factors to be considered when pushing a car to it's limit. I am sure you know all this. There is a point where you can find a balance between your under and oversteer at the high RPM without risking the stability of the car and your life for that matter. Time will teach you where that comfort zone in your car is. Keep driving my friend

    Dec 8, 2005 6:32:20 PM

    SonOfStig
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    Reply to: KiwiCanuck

    Re: Hopping front end syndrome....

    KiwiC,

    I completely understand your issue - the nose does bob - different from pretty much any other motor there is around. However, I've had a little opportunity to play with the car now and I think you can dial this out by driving technique. Although hardly an expert this is what I seem to have found so far:

    * Try trail braking as you commence the turn (i.e. maintain *some* braking pressure as you steer into the turn) - this should help you keep the weight to the front and increase traction, grip and therefore avoid both vertical and especially horizontal bouncing/skipping.

    * Try to maintain moderate pressure on the accelerator as you continue the turn; excessive gas will almost certainly cause you to understeer. Making the car neutral (no gas) feels odd and may cause oversteer in extreme situations, so I prefer to have some drive going through the wheels - and of course you will be then ready to booot it as you unwind!

    Hope this helps,

    SoS.

    Dec 8, 2005 7:50:49 PM

    Paul S in TX
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    Reply to: SonOfStig

    Re: Hopping front end syndrome....

    I've never experienced what you describe on the sweeper--bobbing of the front end nor have I yet experienced the anomaly the car magazines have meationed on PASM equipped 997's, but mine's an 06 (October build) so maybe Porsche tweaked something. And I'm running the 19's which if anything should be "worse" than your 18's.

    Are you being smooth with your hands--as in, negotiating the turn with one smooth turn of the wheel and holding that set, or do you turn wheel and pause; turn some more then pause; etc...One can upset a car's balance as much or more by steering input as you can with throttle or brakes.

    Just a thought.

    Not that this is any news, but like others who've done track events, DE's, PDE and others, I find that if you get your braking (whatever braking you're going to do) done, get off the brakes and on the throttle to maintain a steady state before turning in, it should be smooth assuming your entry speed isn't way too high to start with and you're not being jerky with your steering inputs.

    Also, is PSM intervening on you? I've driven mine very fast around corners I know well and no bobbing and no PSM intervention. When brand new (before my tires got about 500 miles on them), my only complaint was the front end didn't feel as planted as I'm accustomed to, compared to the 996 Turbo I had and the Boxster S I still have as my "other" Porsche. But now the car's settling in nicely.

    Dec 8, 2005 8:03:56 PM

    964C2
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    Reply to: vtach88

    Re: Hopping front end syndrome....

    ....another thing you can do, instead of easing up on the throttle and causing some trailing-throttle oversteer, is to actually unwind the wheel a small amount. This seems counter intuitive, but it actually lets the front tires bite and reduce the slip angle thus reducing the understeer.
    You'll learn this in PDE......

    Dec 9, 2005 12:49:02 AM

    vtach88
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    Reply to: Paul S in TX

    Re: Hopping front end syndrome....

    Quote:
    Paul S in TX said:
    I've never experienced what you describe on the sweeper--bobbing of the front end nor have I yet experienced the anomaly the car magazines have meationed on PASM equipped 997's, but mine's an 06 (October build) so maybe Porsche tweaked something. And I'm running the 19's which if anything should be "worse" than your 18's.

    Are you being smooth with your hands--as in, negotiating the turn with one smooth turn of the wheel and holding that set, or do you turn wheel and pause; turn some more then pause; etc...One can upset a car's balance as much or more by steering input as you can with throttle or brakes.

    Just a thought.




    I'm riding on standard 19inch tires. On the sweeping overpasses, I'm quite smooth with the steering and acceleration - with my eyes on the straight away down below. I doubt I'm pushing my car to the limits - but that certainly is a possiblity....and that would be pretty sad as I'm not really driving that fast ...

    Dec 9, 2005 1:51:10 PM

    john999s
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    Reply to: vtach88

    Re: Hopping front end syndrome....

    SonofStig provided good advice and more eloquently than my post! I do agree with him. The car is certainly more settled either on the brakes or on the gas. Neither brake or gas is bad news and the car can feel worryingly loose. Turning in under heavy braking needs to be smoothly and quickly followed by moderate power to stabilize the car otherwise it will feel very loose can even oversteer/ slide. My experience is that the front bites better on the 997s than the 996C2 I had. If you do a driving day you can explore corner entry speed at lower risk-I think in most cases if you arrive slow and boot the throttle you will get strong understeer followed by oversteer as the rear starts to break away. If you arrive faster, but not too fast and turn in as you are coming off the brakes, with moderate throttle you will not only be faster and kill the understeer, but the vertical motion (bobbing) is much reduced and the car feels really balanced. As the corner opens and the vanishing point opens and you take off the lock-simultaneously get harder on the gas.This works especially well in the wet when the understeer/oversteer can be worse. The most obvious difference when I went from my 996C2 on Michelins to my 997s on the new Michelins was that this could done much much faster before the onset of bobbing -in fact it took me a while to really understand how much faster the PASM C2S is compared to 996C2. But it takes practice. Another post on heel and toeing also gives valuable pointers for this balance. If you heel and toe as you come down the gears you can aslo avoid upsetting balance as you approach a bend and turn in. Even now if I haven't driven it for a while (business abroad)it takes a good long drive to get it absolutely right.I think that its part of the joy of a 911-it remains a challenge.

    Dec 9, 2005 3:15:38 PM

    JJBlade
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    Reply to: john999s

    Re: Hopping front end syndrome....

    The hopping front end does not happen on a non PASM car so some of these posts have gone a bit off track talking about it beiong a characteristic of 997's

    Dec 9, 2005 4:16:32 PM

    Trundle_GT3
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    Reply to: vtach88

    Re: Hopping front end syndrome....

    Quote:
    vtach88 said:
    I've only driven my first P (997S) for 5 months. I haven't had time to take the PDE courses - but plan to in the spring.
    I've had 2 unusual (for me) experiences with my car:

    1) I took a 110 degree turn onto an empty 3 lane road and tried to gun it (I know.... slow and steady accel is the key)out of the curve and I could feel the rear end driving the front wheels (which were still turned a bit) in a straight line (massive understeer) - and the front end just kind of hopped a few times. It was disconcerting.

    2) Whenever I'm taking an curved overpass that is long, sweeping and at highway speeds - I'm bothered by the hopping/bobbing front end - which sometimes seems to be a bit sideways as well as up/down.

    I know some of #1 was my fault - as I learn about the fat rear wheeled understeering characteristics, but #2 bothers me a bit.

    Am I being too sensitive? Is this terribly unusual - or is my car misbehaving?

    Otherwise, I'm totally pleased with the car....




    It is SO difficult to analyze the handling condition as presented in the written word as there are so many factors at play.
    Situation 2:
    The road .... uphill? down hill? crests? Transitions from one to another?
    Expansion joints? road surface? bumpy or smooth.
    Your inputs... abrupt or smooth?.

    The 997 suspension may seem taught and firm however that just ampifies driver inputs (steering, throttle, brake), which must be SMOOTH to best get the car to perform at it's highest potential.
    ie: To progressily roll on the throtle instead of stabing or flooring it. Stabing or flooring will unbalance the car by shifting weight rearward unloading the front resulting in understeer.

    This is where PDE will help you understand vehicle dynamics, the "friction circle" how your inputs can help or hinder the handling of the car and what you want the car to do.

    At PDE, on Barber Motorsports turn 10, a left, is the entry to the high speed esses. Entry is is made just after shifting to 4th depending who is driving entry speed is mid 80's. What is required? a slight lift of the throttle at turn in, to balance the car and set the front end so that it will turn in. A balanced throtle is maintained thru the apex of 10 to the apex of 11 (a right) until you can see the track out point after 11, only then do you begin to soothly and progressivly roll back on the throtle. Terminal speed at track out of 11 is right around 100.

    Really hard to describe, there is so much going on, however, the most important thing to remember is that the controls at our disposal, Throtle, Brake, Steering, are rheostats, not light switches.

    PDE will help you understand that the handling problems that you describe are most likley caused by you, the driver, and not an inherent problem with the car!

    Dec 9, 2005 6:57:31 PM

    JJBlade
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    Reply to: Trundle_GT3

    Re: Hopping front end syndrome....


    Quote:
    vtach88 said:
    PDE will help you understand that the handling problems that you describe are most likley caused by you, the driver, and not an inherent problem with the car!




    The same driver will find the PASM car bobs and the other cars don't. So what has this got to do with the driver? Ansolutely nothing, it is a flaw of the design.

    Dec 9, 2005 10:39:57 PM

    KiwiCanuck
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    Reply to: Paul S in TX

    Re: Hopping front end syndrome....

    You said:

    I've never experienced what you describe on the sweeper--bobbing of the front end nor have I yet experienced the anomaly the car magazines have meationed on PASM equipped 997's, but mine's an 06 (October build) so maybe Porsche tweaked something. And I'm running the 19's which if anything should be "worse" than your 18's.

    Are you being smooth with your hands--as in, negotiating the turn with one smooth turn of the wheel and holding that set, YES or do you turn wheel and pause; turn some more then pause (NO); etc...One can upset a car's balance as much or more by steering input(NO) as you can with throttle or brakes.

    Just a thought.

    This is a long sweeping turn, whose total length is likely 1/4 mile. I am nowhere NEAR understeer or oversteer. This would happen even on a straight road. If it was without undulation, I could imagine turning this at 150kph and I am at 120kph max. No this is PASM----- the Acura TL is completely unfazed by it at 120kph (it is in a 90kph zone!)

    Thasnk KiwiCanuck

    Dec 9, 2005 10:46:16 PM

    KiwiCanuck
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    Reply to: SonOfStig

    Re: Hopping front end syndrome....KiwiCanuck

    You said:

    I completely understand your issue - the nose does bob - different from pretty much any other motor there is around. However, I've had a little opportunity to play with the car now and I think you can dial this out by driving technique. (Not on these undulations --thay are VERY marked, which is why only here has the PASM-997 behaved thus) (Although hardly an expert this is what I seem to have found so far:

    * Try trail braking as you commence the turn (i.e. maintain *some* braking pressure as you steer into the turn) - this should help you keep the weight to the front and increase traction, grip and therefore avoid both vertical and especially horizontal bouncing/skipping.(This corner has 1/4 mile extent ---- I am nowhere NEAR under or oversteer ----this behaviour may as well be on a straight raod. If it was not in a 90kph zone, and were completely without undluation, I could take this at 150kph. I am at 120kph, and the Acura TL is completely happy at 120kph)

    * Try to maintain moderate pressure on the accelerator as you continue the turn; excessive gas will almost certainly cause you to understeer(NOWHERE NEAR THAT). Making the car neutral (no gas) feels odd and may cause oversteer in extreme situations, so I prefer to have some drive going through the wheels(YES) - and of course you will be then ready to booot it as you unwind!

    Hope this helps,(NOT REALLY BUT THANKS FOR TRYING. I AM SURE IT IS THE BELOVED CARRER-PASM ----- BUT IT IS AN VERY UNS\USUAL BIT OF RAOD.

    KiwiCanuck

    .

    Dec 9, 2005 10:49:03 PM

    KiwiCanuck
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    Reply to: 964C2

    Re: Hopping front end syndrome....

    Sure--- one daoes that with FWD cares getting into understeer

    KiwiCanuck

    Dec 9, 2005 10:56:32 PM

    KiwiCanuck
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    Reply to: john999s

    Re: Hopping front end syndrome....

    Thanks John999,

    Please tell me this: do you, in the midst of this great trail and error, experience the rear-end sliding-on-the-suspension ( a lttle internal adjustment of position/ weight) that the US Excellence writers talk of? This as you are getting into the middle of the corner when the g-forces are buidling up.
    Thasnk KiwiCanuck

    Dec 10, 2005 1:37:33 AM

    AeroSmith
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    Reply to: KiwiCanuck

    Re: Hopping front end syndrome....

    Quote:
    KiwiCanuck said:
    The PASM is caught in a dilemma that may not be solvable ---- at lowish speeds (relative to the road undulations that may exist --- that is, a smoothly surfaced road that undulates)the PASM in normal setting gives a nice coseted ride. But cover that same stretch at speed and some of the undulations are firmly damped, others not, as the PASM perceives high accelerations in some cases/or some wheels. This produces a rather unsettled response for the car ---

    ----- in fact under such conditions, the Acura TL (6 spd) with its sports suspension and excellent steering turn-in, is actally faster and more predictable than the C2 Carrera.

    KiwiCanuck



    In Normal mode perhaps. Try sport mode. Wouldn't that be more comparable to your Acura sport suspension?

    Acura TL faster and more predictable than a 997? LMAO. You're joking right? The Acura may be faster and more predictable for you but, no offense, I'd say that is obviously more related to the driver than to the car. After three PDEs and several thousand miles on my 997S, there is no car I find more predictable at speed than a 997. Though I certainly prefer the solid feel of sport mode to normal mode at higher speeds.

    Trundle997s, btw, has completed 10 PDEs. And has absorbed much from the likes of Hurley Haywood and Doc Bundy and Cass Whitehead. He knows his stuff.

    Excellence is a good magazine and I have a subscription. But I'm inclined to give more weight to the Hurley Haywoods of the world. According to Hurley the car's only weakness is the 19" wheels.

    Again, the car may bob in normal mode but when properly damped in sport mode it is quite solid.

    Dec 10, 2005 4:02:58 AM

    doc2s
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    Reply to: AeroSmith

    Re: Hopping front end syndrome....

    hopping is definetly a PASM issue. i experienced it on different tracks. one exmple illustrating it's a PASM issue is at the end of lime rock's straight away before the braking zone at 100+ mph. PASM was on sport setting.

    Dec 10, 2005 1:13:31 PM

    john999s
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    Reply to: doc2s

    Re: Hopping front end syndrome....

    Hi KiwiC
    I'm not sure I agree with some posts which talk about this being a totally PASM thing.
    I think there are 2 issues here;
    1.The vertical motion of the front of a fundamentally lighlty loaded front end due to the rear engine.
    2.The additional motion some have experienced apparently due to PASM programming.
    The PASM behaviour where there is addtional 'bobbing' feels to me like a rear damper stiffens in a not totally predictable way causing a reaction through the rest of the car in response to bumps, speed and corner load. It's difficult to repeat (at least for me) and I've only felt it a few times but since everything else is rather lively anyway it didn't bother me! The rear has stepped out on these occasions but they were mild and one time slips not a full slide at relatively low speeds on a low coefficient surface. Others better qualified than me can provide a better explanation but that's how it feels. I am happy to have this occassional behaviour for the massive improvement in comfort on long runs from PASM.
    In regard to the general behaviour of recent 911's I stick to the view that they all exibit vertical motion of the nose on uneven surfaces or at the limits of front adhesion-but this trait is reduced on cars with stiffer/better suspension settings. PASM genrally reduces this trait except in the case that it unexpectedly stiffens/softens the damping on one side of rear and causes the reaction described by others.

    I suggest do what I did and go and find a nice (wide) bit of quiet tarmac with some bumps and have a play. My favourite bit of road has a mix of dips, crests, bends (some off camber) and bumps to tie most suspension in knots! My 911s does everything my 996C2 did except much faster and with an occasional unpredictable odd 'bob'/slip/'bob'or two. Both cars corkscrew briefly as the suspension settles after a right hand off camber over crest with bumps but the PASM car is harder to predict-but MUCH faster. I am waiting for my dealer to get a -20mm car in to try to see what it'll do on the same bit of road:).

    So in summary I reckon its an inherent characteristic of the car that is masked/amplified by PASM.

    Dec 10, 2005 1:16:50 PM

    john999s
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    Registered on: Sep 10, 2005
    Reply to: john999s

    Re: Hopping front end syndrome....

    RE:This as you are getting into the middle of the corner when the g-forces are buidling up.
    Sorry forgot to answer this bit. It always happens to me when there are bumps and reasonably high lateral forces.(PASM normal) but it has happened at lowish and medium speeds.

    Dec 10, 2005 1:27:55 PM

    JJBlade
    Co-Pilot
    JJBlade
    Loc: UK
    Posts: 190, Gallery
    Registered on: Nov 11, 2005
    Reply to: john999s

    Re: Hopping front end syndrome....

    Quote:
    john999s said:
    Hi KiwiC
    I'm not sure I agree with some posts which talk about this being a totally PASM thing.
    I think there are 2 issues here;
    1.The vertical motion of the front of a fundamentally lighlty loaded front end due to the rear engine.
    2.The additional motion some have experienced apparently due to PASM programming.
    The PASM behaviour where there is addtional 'bobbing' feels to me like a rear damper stiffens in a not totally predictable way causing a reaction through the rest of the car in response to bumps, speed and corner load. It's difficult to repeat (at least for me) and I've only felt it a few times but since everything else is rather lively anyway it didn't bother me! The rear has stepped out on these occasions but they were mild and one time slips not a full slide at relatively low speeds on a low coefficient surface. Others better qualified than me can provide a better explanation but that's how it feels. I am happy to have this occassional behaviour for the massive improvement in comfort on long runs from PASM.
    In regard to the general behaviour of recent 911's I stick to the view that they all exibit vertical motion of the nose on uneven surfaces or at the limits of front adhesion-but this trait is reduced on cars with stiffer/better suspension settings. PASM genrally reduces this trait except in the case that it unexpectedly stiffens/softens the damping on one side of rear and causes the reaction described by others.

    I suggest do what I did and go and find a nice (wide) bit of quiet tarmac with some bumps and have a play. My favourite bit of road has a mix of dips, crests, bends (some off camber) and bumps to tie most suspension in knots! My 911s does everything my 996C2 did except much faster and with an occasional unpredictable odd 'bob'/slip/'bob'or two. Both cars corkscrew briefly as the suspension settles after a right hand off camber over crest with bumps but the PASM car is harder to predict-but MUCH faster. I am waiting for my dealer to get a -20mm car in to try to see what it'll do on the same bit of road:).

    So in summary I reckon its an inherent characteristic of the car that is masked/amplified by PASM.



    How can you summarise by saying you think it is an inherent characteristic of the car that is just amplified by PASM when you have not tried both? I have and can can tell you the -20mm does not 'bob', the PASM car does. This bobbing has nothing to do with the design of the car or the light front end and everything to do with the adaptive dampers of a PASM car. Take PASM off the car and it simply does not bob.
     
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