Crown

track vid

0-300kph

chasing a 997GT2

eclou:
great to hear Alex! Way to represent us rabid TT owners! 

Cheers

OK - got the new settings from Chris.

Apparently I was at max negative camber before and so only 1/3 to 2/3 of the tryres were in contact with the ground.  Great for hot track days, sucks for winter public road driving.  Chris says a lot of his customers come in for winter and ask to have all their negative cambers reduced.  That way they have more of a contact patch of each tyre on the road.  It also means on bumpy b-roads you get less camber thrust and the car feels less nervous.

In the few 1000 miles since I had my Bilstein B16's fitted the rear had sagged by 2mm.  This explains a couple of differences on my original 'final' shots and my new 'initial' shots.  Apparently the stock Bilsteins on all the 997s sag like crazy so the B16's are much better at keeping the same heights over time.

cannga:

Alex,

Very nice! Thanks. And yes I woud be very interested in your final alignment setting. Curious about the toe settings that Chris decided on.

For anyone interested in converting of toe setting from angle (degree) to distance (mm), there is a nice calculator here: http://www.ground-control.com/toe-out.htm
(Notice that the table here is in angle, whereas Alex's earlier post on his car's alignment is in distance.)

Below is a table with conversion already done for a car with 25.5 inch tire diameter (don't know if it's the same as the Turbo's tire):

Here's a Chart For A Popular Tire Diameter

Toe-Out Data For One Tire With A Diameter of 25.5 Inches

Why "25.5 inch tire diameter"???

Suspension set-up systems which measure toe in mm or inches as opposed to in minutes of angle take their readings off the edge of the wheel rim (approx. 19" diameter) and not off the tire. The shape of tire sidewalls is not consistent enough to give reliable readings.

Interesting to compare against the factory settings

I am not sure the Turbo front camber Chris gave me is correct.   I will double check with him

--

fritz:

cannga:

Alex,

Very nice! Thanks. And yes I woud be very interested in your final alignment setting. Curious about the toe settings that Chris decided on.

For anyone interested in converting of toe setting from angle (degree) to distance (mm), there is a nice calculator here: http://www.ground-control.com/toe-out.htm
(Notice that the table here is in angle, whereas Alex's earlier post on his car's alignment is in distance.)

Below is a table with conversion already done for a car with 25.5 inch tire diameter (don't know if it's the same as the Turbo's tire):

Here's a Chart For A Popular Tire Diameter

Toe-Out Data For One Tire With A Diameter of 25.5 Inches

Why "25.5 inch tire diameter"???

Suspension set-up systems which measure toe in mm or inches as opposed to in minutes of angle take their readings off the edge of the wheel rim (approx. 19" diameter) and not off the tire. The shape of tire sidewalls is not consistent enough to give reliable readings.

--
fritz

fritz,

My day job & training have very little to do with car mechanics and hence your inputs are always helpful. I quoted that tire-based calculator for the simple reason that it's the only one I know  .

The web site http://www.ground-control.com/toe-out.htm gives an example of 25.5, which happens to be the Turbo's front tire's "theoretical" diameter. (Rear is 26.2, if my calculation is correct. http://www.1010tires.com/tiresizecalculator.asp)

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

Alex_997TT:

I am not sure the Turbo front camber Chris gave me is correct.   I will double check with him

Alex,

Thanks for posting. Yes the new camber setting seems to be much more like stock, less like the street GT spec.

The other interesting is your toe setting is now toe-IN both front and rear, +6 and +12 minutes. This is more conservative than my presumed PARR (sp?) setting of your car, which was toe-out front (negative value), and toe-in rear.
(Supposedly, front toe in is less twitchy, front toe out has better turn-in response.)

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

cannga:

(Supposedly, front toe in is less twitchy, front toe out has better turn-in response.)

My apologies in advance for butting in yet again.

I cannot claim specialist knowledge of setting up suspensions but I would expect toe-out to be not just "twitchy" but positively wayward, and far from improving turn-in response I would expect it it to delay the building up of steering force in the outer front wheel when initiating a turn, resulting in poorer response.
This would mean that there are no good arguments at all for front-wheel toe-out.

I have a theory (which I have never gone to the effort of testing) that early complaints about poorer steering feel from some buyers of  997s coming from 996 cars was due to toe-in setting range of 997 being changed in such a way that some cars could have zero toe. 996 toe tolerances were such that a correctly set car would always have some toe-in. Just like the GT models in the above table still have in fact.

I remember some rennteamers complaining about on-center steering feel of their 997 and blaming it on new variable-ratio racks, whereas in fact the ratios of old and new racks were virtually identical at center point. I personally didn't have the problem with my 997, suggesting that it probably had slight toe-in.

I guess that non-GT 997s were set up with less toe-in than predecessor to slightly reduce tire wear. Since front tires last much longer than rear ones anyway, that wouldn't be my personal priority. 

No problem -- I appreciate the comment. I don't want to be in a monologue either and sorry for the late response. First, do you have to use such a scary word, "wayward"? How about "alive"?

>>>>>
This would mean that there are no good arguments at all for front-wheel toe-out.
>>>>>>>

No question that there ARE negative trade-offs, but I am not sure I would agree with the above statement. I did not plug the idea of front toe-out promoting steering response out of thin air;  its usage comes from (at least) a couple of the most trusted names in Porsche suspension set-up in Southern California; one sets up my car, the other sets up a friend's Turbo on 6speedonline. I continue to suspect also that this is the one used by Alex's first tuner, PAR of England.

As in all suspension decisions, there are trade-off's (straightline stability, twitchiness), so this much I would agree: a. that this setup is NOT for everyone or very situation, and b. some would argue it's more for a track car then a street car. (OTOH from my experience so far, it is A LOT LESS twitchy or "un-directional" than I had expected. I thought the thing was going to wander all over the freeway; this is not the case at all, at least as set up in my car.)

As for explanation, I would agree that without a professional here, it would be dangerous for me to speculate on an explanation. That said... why not? It's fun, and sort of harmless. You seem to be concentrating on the outer wheel -- and your explanation makes sense to me, but... the articles that I have seen appear to concentrate on the inner wheel. So clearly there are 2 opposing effects, inner wheel effect causing the described quicker turn-in response, that much I would venture.

Besides what was said by my tuner, I have run across several articles expressing the same idea. There is no unexpected "exception" to the rule that I have seen. Here are 2 that I like - sorry I have no access to authoritative textbook:

http://www.ozebiz.com.au/racetech/theory/align.html
....If the car is set up with toe-out, however, the front wheels are aligned so that slight disturbances cause the wheel pair to assume rolling directions that do describe a turn. Any minute steering angle beyond the perfectly centered position will cause the inner wheel to steer in a tighter turn radius than the outer wheel. Thus, the car will always be trying to enter a turn, rather than maintaining a straight line of travel. So it's clear that toe-out encourages the initiation of a turn, while toe-in discourages it.
....The toe setting on a particular car becomes a tradeoff between the straight-line stability afforded by toe-in and the quick steering response promoted by toe-out. Nobody wants their street car to constantly wander over tar strips-the never-ending steering corrections required would drive anyone batty. But racers are willing to sacrifice a bit of stability on the straightaway for a sharper turn-in to the corners. So street cars are generally set up with toe-in, while race cars are often set up with toe-out.

http://www.mgf.ultimatemg.com/group2/suspension/toe.htm
...If the car is set up with toe-out, however, the front wheels are aligned so that slight disturbances cause the wheel pair to assume rolling directions that do describe a turn. Any minute steering angle beyond the perfectly centered position will cause the inner wheel to steer in a tighter turn radius than the outer wheel. Thus, the car will always be trying to enter a turn, rather than maintaining a straight line of travel. So it's clear that toe-out encourages the initiation of a turn, while toe-in discourages it.

Finally, phew, there is actually an active thread where a couple of people mentioning the front toe-out setting of their cars on rennlist. If you still have questions about how it could work, I think that would be a good place to post the question. Those guys are a little nutty but to me are very knowledgeable & experienced: http://forums.rennlist.com/rennforums/997-gt2-gt3-forum/472590-my-gt3-handles-like-a-truck.html

fritz:

....

I cannot claim specialist knowledge of setting up suspensions but I would expect toe-out to be not just "twitchy" but positively wayward, and far from improving turn-in response I would expect it it to delay the building up of steering force in the outer front wheel when initiating a turn, resulting in poorer response.
This would mean that there are no good arguments at all for front-wheel toe-out.

....

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

OK. I assumed that the set-ups being discussed were for cars primarily being used on the street, not track.
I can see that good on-center feel in the steering wheel is not as important on twisty tracks with few or no straight sections. But I certainly wouldn't want to do without it in my normal road driving, and most certainly not on some of the uneven older concrete sections of Autobahn we frequently have here, where every variation of weighting between the left/right front wheels would lead to the car darting off in different directions at the high speeds which are legally permissible. As you imply, toe-out encourages the initiation of turns, even when a car is being driven straight!

The soft suspensions of street cars and higher hysteresis of street tires call for more "anticipation" on the part of the driver in terms of setting up the car for each corner anyway, and for this kind of driving I don't see the benefit of  kart-like twitchiness. 

After extensive weekend spins of late down predominantly bumpy back roads in road conditions a little damp and under 7 degrees C, I have come to the conclusion that I need two yearly settings.  One for winter and one for summer.  The summers maybe 1-2deg neg and winter 0.5 to 1deg neg on the cambers.

Also, for winter I am thinking of changing my GMG sway bar settings from medium F/R to soft F/R.  Currently I am getting a lot of twitchiness under full acceleration - even in a straight line and the car is VERY stiff.  Hopefully another geo tweak from Chris and softer sways will help. Will report after I make the changes in a couple of weeks (when the weather hopefully improves a little - snow here at the moment).

I've done it!!  With the help of Chris I have found 997 Turbo driving nirvana for 'all-road' driving...

These were the tests we did yesterday:

Please note the REVISED PORSCHE FACTORY SETTINGS.  There was some confusion over numbers Chris initially gave me, but yesterday I checked them for myself and revised my tables.  This principally meant all the ride heights I was basing my initial calculations on was wrong!! 

The other thing of note is that in 3000 miles since I fitted my Damptronic kit the car has sagged a LOT.  This means though that by raising the car back up higher the dampeners/springs have more travel and them and the ride becomes softer and more importantly makes the wheels touch the ground more when on rough terrain GIVING YOU A MASSIVE AMOUNT MORE TRACTION ALONG WITH BEING MUCH MORE PLANTED.

The other major change I made was setting the front sway bars to full soft (note still a little stiffer than the stock bars).  The allowed the front end to lean and twist more.  Again this helps with traction and stability over public roads. 

So the car does roll a bit more through corners but the extra compliance is staggering.  The car is so much more confidence inspiring now.  As Chris says in the world of geometry tuning "compliance is king"!

I would HIGHLY recommend everyone with the Bilstein Damptronic kit to go back to your tuners after a few thousand miles after the car has done most of its sagging/settling, and check you ride heights, and adjust the Bilstein's to match mine.  You will be amazed at the difference!  Please note that ride heights should be measured at the Porsche official locations under the car.  Using fender measurements is WILDLY inaccurate according to Chris.

Any questions then let me know.

With regards to ride heights:

Baring in mind the above table...

Factory front = 132 mm +/- 10mm
Factory rear = 153 mm +/- 10mm

First 7500 miles with stock Bilstein's:

Front: 134 mm
Rear: 140 mm

Upgraded Bilstein's (B16 Damptronics) set to:

Front: 119 mm
Rear: 132 mm

After further 3000 miles:

Front: 112 mm
Rear: 128 mm

Reset to:

Front: 117 mm (giving 5mm more travel in the dampeners)
Rear: 138 mm (giving 10mm more travel in the dampeners)

The sagging is worse with stock Bilstein's than the B16 Damptronic kit.  I'd say it takes between 3000-5000 miles before the suspension fully settles.

I should probably post this chart I compiled in this thread too in order to keep everything together:

>>>>>
So the car does roll a bit more through corners but the extra compliance is staggering.
>>>>>>>>> 

Agreed. When I started looking into why my Turbo acts like a Lexus (Is *anyone* at Stuttgart reading this?  I am not the only one complaining. ), I thought simplistically "stiffer is better." Since then I've learned that there is always trade-off: Stiffer suspension is better for chassis dynamics (roll, dive, squat), but could be worse for traction. There is a middle point for both parameters, affected by how and where you are driving the car -- road versus track, etc., that you have to achieve to have happiness.

So you think you were hitting the internal bump stops? I have no personal experience that have read that it could be an extremely unsettling experience.

Re. the stock toe setting, according to an official reading from a Porsche dealer, the toe setting is lower than what you are posting. Stock setting is 3 minutes, not 5. I mention this because 2 minutes of toe could be significant and I've found LESS toe in (smaller number) to be extremely helpful in curing the Turbo's lazy steering response (very lazy compared to GT2). You might want to give minus 2 minute toe out a try once summer comes. I think you'll love it.

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

Can - that print out is for a Carrera 4 not a Turbo

Also, Chris has print out from 2009 PIWIS system.  I copied the GT3/RS, Turbo and GT2 figures.

Also, with regards to toe - you need to bear in mind that when accelerating the wheels actually toe out (more neg). 

So a more powerful car needs more toe in (more positive). 

That's why Shavster in his 700bhp Turbo is running +11 minutes of toe at the front.  Under HEAVY load this comes down a lot.

Alex_997TT:

Also, with regards to toe - you need to bear in mind that when accelerating the wheels actually toe out (more neg). 

Very true that toe in is more stable during accelaration in a straight line. However, when initiating a turn, that is whenever you turn the steering wheel, wouldn't, or shouldn't, your car be decelerating most of the times?

That is, the advantage of better turn-in response from toe-out cannot be achieved since you car won't be accelerating any time that you are initiating a turn? I actually don't know the answer, just shooting the breeze here.

While it might be true that higher powered cars require more toe-in, most US tuners I've seen, including some very big names who prep race and road cars, do use toe-out on tuned cars, alas with hp probably less than 550. But is there some line between 550 and 700 that makes the car require toe-in versus toe-out? Why isn't that line at say 400 hp?

Don't want to belabor the point or be critical here, because bottom line is Nick's car is working very well for him and other bottom line is I am an amateur speculating . But I see significant better steering and turn-in response in my car (it dances - and not twitchy at all -- the hallmark of too much toe out) and just want to share the joy. LOL. 11 minutes toe-in is an unusually large number (lots of tire wear and excessive toe either way, in and out, could be a source of instability) that I've not run across in my reading and I am wondering if there is something else going on that might warrant a (casual) second opinion.

Lastly thanks for the correction; I am a little embarrassed. That !#@$~%^ non-Turbo alignment sheet has been on my thread as an example of a Turbo alignment since day one. I could have sworn it was posted by a fellow member with a Turbo. But that was back in the dark days when these things seem to be so confusing.

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

My turn in is fine Can.  Toe out will be making the front wheels fight eachother always wanting to turn even before you do.  Had that with the Parr set up, and I vastly prefer the heavier steering of toe in thanks.

cannga:

Alex_997TT:

Also, with regards to toe - you need to bear in mind that when accelerating the wheels actually toe out (more neg). 

Very true that toe in is more stable during accelaration in a straight line. However, when initiating a turn, that is whenever you turn the steering wheel, wouldn't, or shouldn't, your car be decelerating most of the times?

I try to decelerate BEFORE the corner myself, not whilst turning.  I then slowely squeeze the throttle through the corner to get more traction.  I then mash the throttle once out of the corner.  So for me I want better grip coming out of corners which means more positive toe. 

The stock Turbo is 5 +/-5 toe in so 6 minutes is still pretty conservative (especially as I have 544bhp on tap which is more than a GT2 - so I should have more toe in that the GT2 both fromt and rear).

--

Wow - I have just been out for a 2 hour spin down some countryside roads and I am delighted to say that sport mode is BACK on the menu!

Now that my Dampeners have been raised up to -15mm from OEM after they spent the last 3000 miles dropping even the Mrs can't believe how much smoother the car is now even over rough potholes at slow speeds!

If you do now find some flat-ish fast roads and engage sport mode then the car immediately sharpens up and leans less through the corners (countering the soft front GMG sways I have set now), all without knocking out your teeth like it use to with the Damptronic kit. ie. it's tolerable again, and not only that, it's fantastic!!

So I repeat once again to anyone who has Bilsteins fitted... After 3-5000 miles go back to your suspension specialist and get them to adjust the dampeners ride height to either -15mm (or I think -20mm would be fine now for those who track a lot).  And please please please insist they measure from the Porsche official ride height places under the car (several times for consistency) as described earlier in this thread, and NOT from wheel arches!!

Boy I love my car now!!  It is now perfect for me in every way

Hi,

 Anyone on the alignment list running on 20" wheels? I've been trying to find out the ideal combination for quite some time. Currently on GMG springs, GT3 sways with tarrett drop links, adjustable rear toe links, and front tie rods.

 Would appreciate any inputs.. Thanks a lot!

 Ronnie

Chris has been busy annotating many of the pictures taken in this photo journal.  I have started to upload some of them to picasa:

http://picasaweb.google.com/alex.997tt/

For example:

--

Thread kindly updated by Eunice to clean up first couple pages. 

Now have clickable thumbnail pictures and also clarified parts fitted on first post