Per the request for comments on the Ford GT, to wit:

The lust for the car goes waaaay back for me. When I was eight or nine, and I first saw the car on ABC's Wide World Of Sports, in black and white (!) taking the win at LeMan's, I was hooked. It was then, as it is now, the most spectacular looking machine I've ever seen. Then about a year later, while riding my bicycle in Brooklyn (of all places) I saw one PARKED ON THE STREET! It remained parked in the same spot for about a month - and I 'visited' it every day. No doubt they had to move it because of the drool marks. Then one day, it was gone. But by then, there was imprinted the 'someday, I have to have one of these' in the back of my mind.

Fast forward to Ford's announcement that they were going to make a 'recreation' for their 100th birthday. When they started building them, I was put off by the price, so thought I'd buy a used one one day. I was shocked when, to their word, Ford stopped building them after they built 4000 of them. I was even more shocked when, a few months after that, the prices started to rise as collectors stepped in. So I thought, 'If I don't get one now, I'll never have one. I'll be priced out of the market'. So I found a used one, with 200 miles, and the rest, as they say, is history.

Cannga's assessment of the car is about spot on. It is brutally and effortlessly fast. For all of you who think their TT's or GT2's are quick, you may have not (nor had I) experienced a truly fast car. It is the only car (and I've sampled the same Lambo's and F-cars that Cannga references) that feels massless and weightless. Wrong gear? No problem. Going up hill? No problem. And because it is so tied down, and so stiff, you occasionally lose the sense of acceleration that the car possesses. And it's very long-legged. First gear is good for 62 MPH - which is one of the reasons the 0-60 times are so impressive. Though my intent is to keep the car stock, I did succumb to the standard 'pulley and tune' upgrade, adding about 100 horsepower at the rear wheels. Second and third gears are truly entertaining. Cruising the freeway, drop it down to second or third at 65 (!) and instantly reach triple digits. Instantly. Remember as well that this is an 'electronic nanny'-free car. No stability, traction, etc. management technologies. Except for ABS, this is a pure direct driver interface car. Which brings me to a bit of Ford GT lore. It has been said that half of all of the totaled FGT's have less than 20 miles on them. One improperly planted right foot in first, second and occasionally third gear, and back and front fight for the lead, usually against a curb, guardrail or worse.

I do take issue with Cannga's comment on handling and road feel. The steering weighting is about the same as the P-car, but the road feel is less than that of a 911 or Cayman or F430. Probably about the same as a Gallardo. It's likely a function of the tire width and the absence of evolution and tuning of the steering system. Remember, the design-to-build time of this car was 18-24 months. It's actually amazing how many things they got right. That said, notwithstanding the terrible tires, the balance and 'stick' is quite remarkable. Makes the 911 rear engined design look just silly. Also, the chassis seems as stiff as the much-acclaimed Carrera GT - or any carbon-based car. It feels infinitely stiff and stable. It's just remarkable. Re the tires, the designers made a huge error in choosing wheel/tire size only in that there are almost no options in selecting alternatives versus the stock tire. In case there is any doubt, the stock Goodyear F1 Supercar tires are anything but. They are remarkably bad. Painfully bad. But to maintain size/width/circumference leaves few choices. And this makes the car very dangerous. At temperatures under 50 degrees, the right pedal is not your friend. Someday, like many owners, I'll upgrade to different rims and put a set of PS2's or Cup tires on the car. In the interim, my next tire will likely be Hoosiers since they have a matcing fit for the stock wheels. Those who own the car have noted that it's a must-have change.

But it isn't a daily driver for sure. First, you need lots of room just to open the doors enough to get in and out. Forget driving it to the mall. The roof cut-outs of the original design (enabling quicker driver changes I think) require the doors to be opened all the way, which is almost 90 degrees, to get in and out. Rear visibility is limited. It is very very low to the ground. Ferrari's and Porsche's look like semi's in comparison. Pretty funny actually. However it is a very comfortable car to drive. Tooling around town or on the freeway, you would never know what is lurking behind you (i.e. under the hood - known as the 'clamshell'). Great seats and driving position, quiet interior, functioning a/c and heat, good stereo (or so I hear, I just listen to the supercharger and engine).

Most of all it's not a DD because it's a to-be-classic. 4,000 made. Numbers shrinking as people find out that the right pedal isn't always your friend. Impractical as cited above. But to me, the most beautiful car ever made, and I plan to keep it that way. I've put 1,200 miles on mine since purchased and I don't plan to drive it more frequently than that. Silly as this sounds, I peek in to the garage now and then and get the same feel that I did when I was a youngster on my bike and saw one on the street. That alone is rewarding enough.

But it is a thrill and I feel honored to own one. A piece of (recreated) history and perhaps the last pure supercar to be built in the U.S. Believe it or not, I let as many (competent) people drive it as I can (short rides with me in the right seat) so they can appreciate great design. Cars like this are to be shared and appreciated.  I'll post photos of my gal one of these days. I hope you will think it's as magnificent as I do.

Finally, like all of you no doubt, I have 'a list'. Those cars that someday I would love to 'collect'. Included (in priority order) are: Porsche Carrera GT, Pagana Zonda, Gumpert Apollo, and a number of others.  At least the one at the top of the list, the Ford GT has been fulfilled :)

Verde,

Thanks for taking the time to answer and congrats on the good fortune to own such a classic. Don't mind too much my nit picking; fact is I love that car and fell in love in a "bad" way . I remember being shocked, that every thing just seems to be so inherently right about the car. There is no question that if the Ford GT has the same daily drive friendliness (and it can't because of what it is), I would take it over the Turbo.

And yes, at the end of the drive, I was just standing there, looking at it, looking at it, and looking at it. Totally oblivious of the Lambo and F car in company. It's so beautiful, it was sad to walk away knowing you may not drive one again.

Regards,
Can
997 Turbo + Bilstein PSS10 (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

Update of some spring data. Someone actually found the rates for the Eibach springs.  Eibach of course is the same company that makes the Turbo springs for GMG and TechArt (doesn't mean they are all the same). As mentioned, this type of data is extremely rare and this is the first time that I've seen someone disclosing them.

I post the rates here because one, it's interesting to see what Eibach thinks (notice how stiff!!), and two, it's an example of a progressive spring's two spring rates. Progressive springs start out with a milder rate and stiffens as the compression increases.
(Knowing that, when you hear a vendor stating such and such spring is softer than his, it's important to inquire, which rate it is he's talking about. A progressive spring could start soft but stiffens to a much higher rate and without full disclosure, it's difficult to judge.)

When comparing spring rates, note that GT3/GT2 is around 300 lbs lighter than Turbo.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Eibach After-Market Springs for 997 Turbo -- Sport Spring Part # 7220.140:
Front: Initial 168 Final 300
Rear: Initial 460 Final 796

Bilstein PSS10 Damptronic for 997 Turbo
Front: 285 Main, 115 Helper
Rear: 570 Main, 145 Helper
Helper springs are fully compressed when installed, so effective rates are LINEAR 285/570.

Stock 996 TT:
Front: 187 Progressive
Rear: 340 Progressive

Stock 997 TT: No numbers available, but probably similar to 996 TT numbers above.
Front: Progressive
Rear: Progressive

Stock 997 GT2
Front: Linear
Rear: Progressive

Stock 996 GT3:
Front: 225 Linear
Rear: 550 Progressive

Stock 997 GT3:
Front: 257
Rear: 600

Regards,
Can
997 Turbo + Bilstein PSS10 (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

Can, I ran across this the other night on call, courtesy of BobK on 6speed...

"Spring Rates, ( courtesy of our superior car Builder/ Bill Pfister @ Eurotech)

Stock 997TT: Front:210#/in.
Rear: 450#/in.

Biltein damptronics as received:
Front: 340#/in
Rear: 675#/in

Obviously why the dramatic improvement!!!!!!!!!!!

Bill said this was the stiffest pss9 /damptronics set he has seen(50%ftont / 60%rear stifer) . He stated that typical is in the 30-40% range. Just another variable!!!!!! "

Doug

Houston, Texas USA 

997TT

TT Gasman:

Can, I ran across this the other night on call, courtesy of BobK on 6speed...

"Spring Rates, ( courtesy of our superior car Builder/ Bill Pfister @ Eurotech)

Stock 997TT: Front:210#/in.
Rear: 450#/in.

Biltein damptronics as received:
Front: 340#/in
Rear: 675#/in

Thanks. The strange thing about BobK's numbers though is that they are much higher than the "official" rates for both stock Turbo (approx. 187/340) and for Bilstein (285/570).  I posted in that thread pointing out the discrepancy, but to this day don't know why it is so.
What remains about the same is the difference: Compared to stock, Biltein is about 100 higher in front, 200 higher in rear, per both official measurements and BobK's measurements.

http://www.6speedonline.com/forums/997-turbo-gt2/131135-997tt-suspension-pt-1-a.html

Regards,
Can
997 Turbo + Bilstein PSS10 (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

All you need to know about springs -- just kidding, only some basic amateur level info here. First the picture: left is Bilstein coilover, right is the stock unit. Both are for the rear and come from eclou's excellent thread on Bilstein installation. BTW, this thread was (is?) for a long time the first thing that comes up when you google something like "Porsche Bilstein PSS10" .

Note that the stock spring is progressive: You could tell by the variable distances between the coils. A progressive spring has two rate, an initial one which is soft, and a final one which is stiffer. This allows a soft and more comfortable rate at first and then a change to a second rate that is stiffer.
I don't want to make this too complicated so I'll stop here but actually there is a further differentiation into step linear spring versus progressive spring. If interested you could read about it here: http://www.tuninglinx.com/html/suspension-springs.html

The Bilstein has 2 stacked springs, a main spring and a second, smaller one. The main spring is linear -- one rate only. The main spring of the Bilstein is of "standard" size and therefore allows you to switch and experiment with different springs and rates easily; replacement springs don't have to be Bilstein. Linear springs are more likely to be found in track applications and instead of arguing with me, you could google "linear progressive spring" and read all about it.
The second spring of the Bisltein is called the Helper Spring. It is fully compressed once installed and therefore does not contribute to the spring rate. The spring rate of the 2 stacked springs is in effect that of the main linear spring.

--

Regards,
Can
997 Turbo + Bilstein PSS10 (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

The erroneous title of this thread is causing a lot of confusion. Wonder if a mod could change the title for me please; it should read Bilstein B16  Damptronic: A Must For The Turbo? (B16 not PSS10, and no "s" at the end of Damptronic.

Anyway, someone just asked me about the 2 versions of the B16 Damptronic coilover in Europe. In the US we have only one, in Europe apparently there is a Comfort and a Club Sport versions? Supposedly with the Comfort version, the Normal mode is softer than Stock Normal? If so, that's not good!

Alex, or anyone, could you shed some light on this? TIA

Regards,
Can
997 Turbo + Bilstein PSS10 (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

Well Cargraphic use to say that the Damptronic kit come in normal or clubsport variants...

• GA5-D598 Sportsuspension B16 damptronic, FA+RA 15-35mm CLUBSPORT/
• GA5-D581 Sportsuspension B16 damptronic, FA 25-35mm, RA 15-35mm /
  

I fitted the Clubsport version.

HOWEVER now when you go to the  Bilstein site it says the D581's are for Carrera 4 and the Turbo you only have a choice of the D598 or the non-PASM PSS10 kit (GM5-D601).

So I guess everyone here with Damptronic kits are either running the Carrera 4 soft versions or the correct Turbo version.

I would also add that it looks like the more you lower the car (15-35mm) the harsher the ride will be over uneven surfaces.  Something that could certainly explain why Cannga is currently happier with his road set-up than me (I am -20mm and he is -10mm).  I shall be moving to -15mm shortly.

Also, everyone should bear in mind that all Bilstein's - stock or upgrades - sag over the first few 1000 miles.  So you should go and get your ride height checked after the sagging has settled.

cannga:

The erroneous title of this thread is causing a lot of confusion. Wonder if a mod could change the title for me please; it should read Bilstein B16  Damptronic: A Must For The Turbo? (B16 not PSS10, and no "s" at the end of Damptronic.

I'm not a Mod, but I have changed the title for you.

You can, in fact, do it yourself just by clicking into the title box when adding a post to a thread.

PS:  I hadn't intended to change the title for earlier posts in the same thread. Using RT1, the title used to be "dynamic",, and changes during the life of the thread would be "documented":

@ Eunice:   HILFE!!

fritz/cannga: I changed the title.

Here on RT2.0 the title is set by the first post in the thread, but that easily could be changed to the last post of the thread. 

The original poster can edit the title for 60 minutes after starting the thread, afterwards only a moderator can do it (by editing the first posts subject).

If you want to suggest this to be different, please start a thread in RT Development.

fritz/Eunice/Alex,
Thanks a bunch!

Nick,
Are you reading Alex's post above? Show yourself. LOL. Anyway, looks like Club Sport is the one you should get. Your car has so much horse power I would think the stiffer suspension is the way to go. (I once sat in a Protomotive tuned car - AAHTT's Turbo. I think there are sitll my finger marks on the door handle of his car. Very scary. )

Regards,
Can
997 Turbo + Bilstein PSS10 (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

cannga:

Note that the stock spring is progressive: You could tell by the variable distances between the coils. A progressive spring has two rate, an initial one which is soft, and a final one which is stiffer. This allows a soft and more comfortable rate at first and then a change to a second rate that is stiffer.
I don't want to make this too complicated so I'll stop here but actually there is a further differentiation into step linear spring versus progressive spring. If interested you could read about it here: http://www.tuninglinx.com/html/suspension-springs.html

The Bilstein has 2 stacked springs, a main spring and a second, smaller one. The main spring is linear -- one rate only. The main spring of the Bilstein is of "standard" size and therefore allows you to switch and experiment with different springs and rates easily; replacement springs don't have to be Bilstein. Linear springs are more likely to be found in track applications and instead of arguing with me, you could google "linear progressive spring" and read all about it.
The second spring of the Bisltein is called the Helper Spring. It is fully compressed once installed and therefore does not contribute to the spring rate. The spring rate of the 2 stacked springs is in effect that of the main linear spring.

So if the Helper Spring is fully compressed, why do we need it at all? It's there to hold the main spring in place (its seat) during full extension of the coilover -- think airborne as an extreme example. This prevents the spring from making noise when you're having fun. (er yes I think airborne = having fun )

Tender Spring: If the second spring is NOT fully compressed with static load, it is no longer called Helper Spring. It's now a Tender Spring and this stacked springs setup is now much different. A tender spring is actually much stiffer than a helper spring and by definition is not in total bind (fully compressed) like the helper spring at static weight.
How is the setup different? It now has 2 effective spring rates, an initial rate, and a second rate. If the main spring rate is a, and the second spring rate is b, then:
Intial rate = b x (a/a + b)     (fritz or someone checks the math for me )
Final rate = a

If you are thinking wait a minute, isn't this just like a progressive spring? Bingo. To make matters more interesting, I  have even read that the tender spring could itself be either linear or progressive.

BTW, all after-market coilovers for the Turbo that I've seen  have similar configuration to the Bilstein: stacked springs. In the Bilstein, the second spring is a Helper; whether it is Tender or Helper in these other setups, I don't know. I remember reading JIC Cross has a spring rate of 900+ in the rear (extremely high) and keep wondering if it is in fact a Main + Tender setup.

Regards,
Can
997 Turbo + Bilstein PSS10 (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

Ok first of all a big thanks to Can and Alex and George (GT)

I ordered today tha ps16 damptronic clubsport version with  Gt2 rear sway bar.. (I didnt order sway bar for front as some friends told me that the stock in front will work much better that any other in awful slipper and bumpy Greek roads.
I will find out when i place mu suspension if i did right... :)
(Alex these people also told me that you should place your front sway bar to soft for your problems) or even place again the stock...

I am also ready to order GMG Toe Steer Kit and Dog bone kit..
and finaly I will order the front - rear lower control arms from 997 cup for future track days.. :)  

I believe that i will have my car set in 10-15 days... I will let you know for sure... Till then i will read your comments about the aligment... The difficult part is to find someone in Greece to corner balance my car...
I hope i bought the best suspension for this car as i am also a fun of KW suspensions..

Nick

KW is meant to be 'better' but then you lose PASM normal/sport button functionality.  Bilstein make the stock dampeners so upgrading to their top of the range keeps the PASM functionality like a stock car.

Also, with regards to sway bars; yes, GMG recommend soft front and stiff rears.  However this is to reduce under-steer and make the car over-steer more.  Having medium f/r seems to be more balanced from what Cannga and others have said.  I am going to try the GMG recommended set-up in a few days time when I will be visiting my tuner for some tests.

Agreed. And to add some data points: What we (GT and I) also found out -- independently of each other -- is that that rear sway bar setting affects ride quality A LOT, particularly if you use a metal joint (aka Heim Joint US, Rose Joint UK) drop link like Tarett instead of  the rubber stock link. In my case it was so stiff that I actually had it taken to the medium setting solely for that reason. It was really intolerable.

Every time I talk to a tuner (all very well known ones), it seems the first thing they mention is soft front/stiff rear sway to reduce understeer. In reality, I am surprised, perhaps partly due to my inexperience and partly due to my setup being so stiff that I couldn't feel anything else , to find out that the effect of sway setting on understeer is not nearly as significant as the alignment change of  more front camber and front toe out.

In fact, I also found the overall effect of the GMG sway to be surprisingly subtle (minimal). It was actually the first mod I had on my car, before the Bilstein. I thought it would reduce the leaning significantly. At  med/med setting, all l I found was a very slight lean reduction and slightly tighter steering feel and response. Very subtle. In retrospect, sometimes I think I could just replace the drop link and keep stock sway because maybe putting a solid joint has the same, or more, effect than replacing the sway itself..

Alex, let us know your impression when you have the change. I am very interested.

Regards,
Can
997 Turbo + Bilstein PSS10 (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

cannga:

 

All you need to know about springs -- just kidding, only some basic amateur level info here. First the picture: left is Bilstein coilover, right is the stock unit. Both are for the rear and come from eclou's excellent thread on Bilstein installation. BTW, this thread was (is?) for a long time the first thing that comes up when you google something like "Porsche Bilstein PSS10" .

Note that the stock spring is progressive: You could tell by the variable distances between the coils. A progressive spring has two rate, an initial one which is soft, and a final one which is stiffer. This allows a soft and more comfortable rate at first and then a change to a second rate that is stiffer.
I don't want to make this too complicated so I'll stop here but actually there is a further differentiation into step linear spring versus progressive spring. If interested you could read about it here: http://www.tuninglinx.com/html/suspension-springs.html

The Bilstein has 2 stacked springs, a main spring and a second, smaller one. The main spring is linear -- one rate only. The main spring of the Bilstein is of "standard" size and therefore allows you to switch and experiment with different springs and rates easily; replacement springs don't have to be Bilstein. Linear springs are more likely to be found in track applications and instead of arguing with me, you could google "linear progressive spring" and read all about it.
The second spring of the Bisltein is called the Helper Spring. It is fully compressed once installed and therefore does not contribute to the spring rate. The spring rate of the 2 stacked springs is in effect that of the main linear spring.

--

Regards,
Can
997 Turbo + Bilstein PSS10 (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

Actually what this looks like is Eclou's progressive Techart spring on his old stock PASM shock. The stock are usually black colored with a couple of stripes for identification. The stock rears also look to be linear, or only very slightly progressive, nothing like the TA or H&R.

Re the sway bars, FWIW  Ruf uses  only a rear sway bar (GT2) on the AWD Turbos, stock up front. 

Doug

Houston, Texas USA 

997TT

Thanks Doug for the correction. If you (or anyone) has the stock spring picture, please feel free to post. Mine is all wrapped up in the Yakima in the back garden and I am afraid of spiders .

What's your impression of the GT2 sway?

Regards,
Can
997 Turbo + Bilstein PSS10 (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

Doug

Houston, Texas USA 

997TT

More ramblings!
Among us non-trackers, it seems one of the most important component of the suspension, tire pressure, is also the one of the least discussed.  Our cars come with an incredibly useful system to evaluate this and If you are not using the TPMS in your car at all, you might want to give it a try. In short, the magic of TPMS is that it recognizes change of pressure with temperature (Charles' Law for the nerds among us), and continuously monitors whether the car's pressure follows Porsche's recommendation.
Basically, in my opinion it is important that the differential reading -- the one obtained by the stalk, and available only when the car is parked -- be zero at all 4 corners.
(The absolute reading has much more variability - due to impacts from road irregularities and leaning of car, etc. while car is moving I think -- and is of extremely limited value to me.)

Even for an amateur like me, in the context of daily street use and weekend fun runs, I have found that increasing or decreasing pressure by even 1 psi results in easily noticeable and reproducible changes in the car's ride and the feel of the suspension.
For example, over-inflating (seemingly very common mistakes among dealers and even tire shops) give a good firm sensation in the short run, but affects negatively ride and traction in the long run. Yes that interesting floating sensation of the rear tires. Conversely if you constantly over-inflate your tires so that your car feels firm enough for you, this might be the telltale sign that you need to add stiffer springs to the car. I know because I used to over inflate my Turbo by 2 psi before I added the Bilstein. At the time, I didn't know; I was a confused man. 

In particular, during my time tuning the suspension system, I find it even more critical that the tire pressure be held in recommended range. That is, since it is a variable that affects the rest of the suspension, you have to hold it within a reference range so that the effect of other components could be properly evaluated.

Next post: recommended toys!

Regards,
Can
997 Turbo + Bilstein Damptronic (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

If you want to experiment, I've found the 2 components to be critical:

Digital Tire Pressure Gauge. Fabulous quality and joy to hold and to use. This reads to .1 psi could be re-calibrated if necessary. A digital gauge to me is much more helpful than an analog gauge. For one, it is vastly easier to read.
http://www.longacreracing.com/catalog/item.asp?id=982&catid=8

Air compressor. Could be found at a very cheap price ($150 or so I think) at places like Home Depot. Very convenient and an absolute, absolute must if you're the OCD type .

Regards,
Can
997 Turbo + Bilstein Damptronic (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

Can,

You get the brass ring! I now have a use for my creeper. Makes it much easier to haul my compressor around. Brilliant idea, since I don't use it as it was intended.

Larry

Over the Hill:

Can,

You get the brass ring! I now have a use for my creeper. Makes it much easier to haul my compressor around. Brilliant idea, since I don't use it as it was intended.

Larry

Regards,
Can
997 Turbo + Bilstein Damptronic (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

cannga:

If you want to experiment, I've found the following 2 components to be critical:

Digital Tire Pressure Gauge. Fabulous quality and joy to hold and to use. This reads to .1 psi could be re-calibrated if necessary. A digital gauge to me is much more helpful than an analog gauge. For one, it is vastly easier to read.
http://www.longacreracing.com/catalog/item.asp?id=982&catid=8

Air compressor. Could be found at a very cheap price ($150 or so I think) at places like Home Depot. Very convenient and an absolute, absolute must if you're the OCD type .

Armed with the above 2 toys, I've done the following interesting experiment:

Adjust the tires' pressure so the TPMS differential readings are 0 at all 4 corners. Use a digital (NOT analog) tire gauge, confirm that the tire pressures are equal between left and right side. Ignore the abolute reading of the TPMS as it has too much variation; all you care about is the tire gauge and the differential reading.

Drive the car for a couple weeks like this.

After several times driving the car, increase pressure, using the digital tire gauge (NOT the TPMS) by 1 psi all 4 corners.
I think that you will be amazed by the change induced by 1 psi change. If you don't feel anything, then your buttock dyno's sensores are in need of re-calibration. Seriously.

As mentioned, I think over-inflating is a common "mistake." Car feels firm and good in the short run but once warmed up will be too hard with poor traction. At appropriate pressure, my car absorb bumps (for example those little round discs on freeways to separate the lanes) without too much fanfare or noise. The tire feedback once warm up is fantastic yet the car doesn't feel harsh at all. I could feel them road grooves.

Regards,
Can
997 Turbo + Bilstein Damptronic (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

The alignment changes in my Turbo are geared largely, almost singularly, towards reducing understeer. Following is a nice discussion why cars understeer or oversteer: http://www.autozine.org/technical_school/handling/tech_handling_4.htm . The concept of slip angle is explained and emphasized.
(Found on the net: If you see the tree before you hit it it's called understeer; if you only hear and feel the tree it's oversteer. ) Anyway, here's part of the article:

Neutral / Understeer / Oversteer

We often hear these 3 terms in car magazines. I think few people would argue if I say they are the most important elements in the study of handling.

What is understeer ? Basically, if you turn the steering wheel and find the car steers less than you expect, the car is understeering. This is not because your subjective judgement goes wrong, in fact any car must have some degree of non-neutral steering due to the weight distribution, suspension design, tyre used, lateral acceleration and road conditions. Further more, a car could understeer in this corner and then oversteer in that corner. The whole picture is very complicated, so I'll spend more paragraphs to discuss this topic.

What do we need ?

It seems that neutral steer must be more desirable than understeer and oversteer, but in fact it is not.

In fact, when running in straight line, we want a little bit understeer to make the car stable. When the car is subjected to side force, probably due to cross wind or the road's irregularities, understeer could resist the force and avoid the car to be steered automatically, therefore the driver need not to correct the steering frequently.

When the car is entering a corner, we also need a light understeer to provide the stability while the driver is easing off the brakes and building up cornering force. In mid corner, we need neutral steer. In the exit phase, a slight oversteer will be welcomed as it helps tightening the path. However, the degree of oversteer must be progressive and easily controllable by applying and easing throttle. We call this "Power Oversteer". Without power oversteer, we have to ease the throttle (thus loss time) or the car will run out of the corner.

However, I must make clear that what I say "slight understeer / oversteer" is usually deemed to be "near neutral steer" by most car magazines. This is because in reality there are too many cars running on severe understeer thus they used to them. In other words, if a car magazine said the Porsche 996 has mild understeer, it probably equals to "medium understeer" in our sense.

Basic Concept : Slip Angle

Before going on our study, we must understand the concept of slip angle first.

When a car enters a corner, all the tyres are turned with respect to the ground. Due to the elasticity of the pneumatic tyre, the tread in the contact patch will resist the turning action because there is friction generated between the rubber and the road surface. As a result, the treads on the contact patch will be distorted, whose direction always lags behind the direction of the wheel ( See figure in below ). We call the angular difference between the treads and the wheel's direction as Slip Angle.

Note : the car is turning left

In which direction the wheel is running ? It is the direction of the tread, not the direciton of the wheel. I am not saying the tread has any ability to force the wheel to travel in its direction. On the contrary, the tread is only a sign showing how an arbitrary point on the tyre surface travels. If the arbitrary point travels in that direction, so does the wheel which is the summation of thousands of those points.

Now you must think the existence of slip angle must reduce the car's steering angle thus leads to understeer. In fact, it is not so if everything else are perfect. Because both the front and rear tyres have more or less the same slip angles, they counter each other thus the resulting steering angle remains unaltered.

However, if the front and rear wheels have different slip angles, then we get understeer and oversteer :
 

Understeer : Front Slip Angle > Rear Slip Angle

Oversteer   : Front Slip Angle < Rear Slip Angle

Neutral steer : Front Slip Angle = Rear Slip Angle

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Regards,
Can
997 Turbo + Bilstein Damptronic (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

I just installed my new suspension... I also placed the 997 gt3 Cup lower control arms, in order to place as much camber i need (Front and back), GMG Toe stir kit and GMG Dog Bone kit.. I also placed back the Gt2 swaybar.
I am really huppy with my car...

I have in front toe -0.01 (totaly different steering wheel) much much better...

camber -1.3

Caster +8.00

Back Toe +0.10

back Camber -1.7

I reduced the height of the car only 15mm and my Gt2 swaybar is soft (because i use the toe and dog bone kit) ..

Sounds all good Nick!

Would be interested in hearing further impressions when you have done a few hundred miles.

Congrats

Nick_Athens:

...

I have in front toe -0.01 (toe out, right?) (totaly different steering wheel) much much better...

camber -1.3

Back Toe +0.10

back Camber -1.7

I reduced the height of the car only 15mm and my Gt2 swaybar is soft (because i use the toe and dog bone kit) ..

Fantastic!

We actually now have near identical settings -- not a bad thing  since the people who set up my car is one of the most trusted and well known Porsche tuners here in Southern Cal -- Lucent Motorsports.
From day one,  Lucent complained that my car doesn't "rotate" (rear end doesn't come out with power when exiting corner -- no controlled throttle oversteer). The front negative camber and negative front toe-out take care of that. And how!
The other advantage of the front toe out is that the steering is much more sensitive and direct, much much more like the GT2. (The steering behavior of the GT2 was the shock that started this thread.) I again would suggest to other Turbo owners to consider this setting. A number of very reputable Porsche tuners in the US are doing the same independently of each other.

Before the mod, I used to fret that my Turbo is not that good when I passed other sports cars. Now... what I do could be easily misunderstood as a condescending smirk. It really is just a contented smirk.

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Regards,
Can
997 Turbo + Bilstein Damptronic (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)

My car is 700hp.. it is much better now... i couldnt drive it with my stock suspension anymore.. I can compare it before with a very very fast, not so sport car and now it became a sport car.. I agree with you on that... What kind of tires do you have ?? I use Pirelli Corsa.. It is the only way for me to go.. (since i modified my vtgs) 

Although now i bought Toyo 888r (semi slick again) which i will put next week and let you know...

Nick_Athens:

My car is 700hp.. it is much better now... i couldnt drive it with my stock suspension anymore.. I can compare it before with a very very fast, not so sport car and now it became a sport car.. I agree with you on that... What kind of tires do you have ?? I use Pirelli Corsa.. It is the only way for me to go.. (since i modified my vtgs) 

Although now i bought Toyo 888r (semi slick again) which i will put next week and let you know...

I still have the stock Michelin PS2. I was going to try the Corsa or Michelin Cup but the tire dealer talked me out of it. They say since I don't track there is no reason to suffer from the increased stiffness and cost (last about half as long?). In the back of my mind, I still want to give it a try some time. Just to see what it feels like. Does it feel much stiffer than stock?
Did the increased power from the modded vtg force you to use Pirelli? Why is that?

BTW, every time I exchange postings with you I can't help thinking about Thanasis and Savas. My oh my what souvlaki heaven! In fact  my  salivary gland is working over time as I am typing this post.  

Regards,
Can
997 Turbo + Bilstein Damptronic (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Review)