MP4.2+6.0

Circa 2007 in the US newer labeling rules came in for US cars. Driven by the Explorer roll over debacle. The newer stickers are the white ones, with black, yellow and red elements that have to be on the driver's door jamb. Earlier they were more commonly on the fuel tank lid on Audi's, though sometimes elsewhere. Thus on D3 A8's, there will be some of both; on S8's I think they are just the new ones.

The relevance is under the "new rules" manufacturers often raised the pressures yet further to comply with the underlying tighter rules on load testing and heat related issues--again, think lowest common denominator here with things like Explorers with high aspect ratios, smaller wheel sizes, heavy chassis weights, and top heavy to start. I first saw the issue more clearly when posters on the Phaeton and other various low volume VW's happened to notice changes in the settings from one year to the next, and one market to the next. Post U.S. stickering change seemed to be the most common element in common. Meanwhile, since my Audi has the pre-2007 sticker with the range of pressures depending on exact tire fitment and load and passenger count being carried, I buy into it more than the newer stickers that have been tweaked for Explorer type lowest common denominators.

s4master1

I actually agreed with you on this only up to a point, again apples to apples.
racing tires are designed to actually deform fast and reshape slow for surface contact and traction, if they lost contact in a turn it can be catastrophic for the car/driver/s and the sport in general.
However those tires are designed to not last more than 200km if use longer than that they lost their abilities of adhesion.

there's other choices for the steering rack as you can see on newer audis, the rack is at the bottom, at which point is not affected by height as much as earlier cars, the reason why is that with this set-up the rack and the lower ball joints stay at the same geometrical angle compared to the upper set-up where the rack moves with the upper arms and by the angle of the shock/strut it changes the toe inclination and affects the camber positive or negative depending which way the height is adjusted.

By the way, A8's upper and lower links are of a very similar length what makes Camber pretty constant. It doesn't change with height. Not for much for sure.

there's nothing constant on these arms, upper and lower, each arm performs an specific function on managing the suspension angles requested by weight applied and turning angle required by the driver.
remember in equal "A" arm suspension there's only one upper and one lower ball joint at each side, with Audi we have 4 at each side and they actually overlap each other sideways, both upper and lowers.
that means when you turn the steering on "A" arms they just rotate in their own axis vs here one moves inward and the other outer to help tilt the wheel.

the 40 years common was based on the fact that things didn't move that fast then when it came to commercial technology, considering those were some of the best years in engineering.
however later in time with the aid of computers advancements became so huge and fast at every level.
and believe am just as old when it comes to cars, but most of my experience was on the BMW 2002,3.0. BENZ 450,280. jaguar xke, MG (mechanized garbage), some peugeots, renaults, and i as you miss some of the fiats, lancias and alfas. My earliest Audi I work on was the 100ls,(onboard brake rotors, good times)was in the middle of the unintended acceleration and even was interviewed by one of the major newspapers (never published,probably because they didn't like that I actually defended the car and compared to the bmws and benzes at the time having the same issue).
my first car was COUPE GT,(the memories), more audis than I can count with fingers thru the years.
never actually left the product but like anybody else had to make a living so went to BMW and BENZ at different times.
When the news were released about The A4 line-up coming to the States I was personally invited by the owner of one of the premier Porsche Audi dealerships in LA to joint the team, without hesitation jump on it in may of 1995.
16 years later Am proud to claim ownership of the largest Audi independent shop in LA, which with the help and encouragement of my wife and son we build from scratch and continue to grow thanks to the loyalty of my customers which is never taken for granted.

mishar

Apples to apples by all means. "Deform fast and reshape slow" is an interesting concept. How does it work? I mean broken down to some well known lows of physics.

I think that lost of contact in a turn is way more catastrophic for an average family than for any racing driver.

You are right. They do not last long. That's because of extreme tensions and very soft rubber that "sticks" to the pavement. Same tires would last much longer on any street driven car. Main problem would be total lack of grip when cold. Almost undrivable under normal traffic conditions.

There I lost you again. Steering rack can be positioned at the top, bottom or anywhere in between, in front of suspension or behind it. All those concepts are equally good or bed compromise. It is fairly simple 3D geometry and it is never perfect. Some other steerings has better geometry but not perfect eater.

You are right about complexity of A8's steering kinematics, but if wheels are strait and you lift or lower the car Camber wont change. Not for much for sure. I will measure it tomorrow.

Nice. I know that you are in this car business all the way. I am glad that you are successful and I wish you all the best with it. I also noticed that you have very substantial knowledge about this cars and I am willing to learn from you. I just do not understand parts when you start to sound like car dealer explaining technology. May be you think that I (we) would not understand if you go to technical.

Brozee

Well back ON subject haha.

I upped the psi to 40 all around. Haven't noticed any harsher of a ride, although with the temps still pretty chilly here in michigan, the MMI reads the rear tires hovering around 38-39psi when starting off and the fronts still around 37. But the tires do look pumped up a bit more, and seem to take a bit of the lean off the outside.

s4master1

Apples to apples by all means. "Deform fast and reshape slow" is an interesting concept. How does it work? I mean broken down to some well known lows of physics.
Laws of physics do apply as on just about anything, specially when is something that change speed fast (race car), let's just talk "G" forces and center of gravity on the total mass of the car and tell me where a passenger car even comes close to a f1 for example?
tires deform to gain the shape of the surface they are in contact with to accomplish the most adhesion/traction/braking possible, the word slow is just used by comparison as they reshape quite fast as well.
that's where your opinion about tall tires comes into play and makes perfect sense, with a low profile tire at high "Gs" the car would just spin due to lost of contact/traction, still just because they are tall the driver is not exactly having a comfortable ride.
on a passenger car specially a heavy sedan is prohibitive to accomplish the same acceleration forces as a race car, if this could be possible the tires would just dismount themselves at take off or during a turn.
see your point on looks before functionality makes sense by all means and eventually we all may just start using taller tires due to the condition of most highways.
sorry if I sound too technical but am not, at this point those terms are so well known in the automotive industry that are used so commonly that I don't know any other way,
you can see how cars have evolved over the years, and so are the procedures/tools/equipment to repair them.
just think the reason hunter and other alignment companies went from inches/mm to degrees.
nowadays all angle are measured in degrees. I still remember old guys adjusting suspensions with a string and a level bar, those guys as well the ones that didn't want to give up carburators became dinosaurs as new technology came along.
transitions have always been painful but at the end makes things better/easier more efficient, now is so much easier to be a mechanic than 20 years ago but still basic principles apply as the internal combustion engine is so old is almost laughable that has not really changed.
I never been much of a racing fan or a car guy at all I just believe in doing one thing and doing better than anybody, every year I get 4 free tickets from Porsche for the Long Beach grand prix and never attended, my son however is getting more interested in the sport and we are looking into an internship at the Porsche factory in Germany.

jakematic

Based on this and the other tire thread I went to 40 all around too.
Ride is fine, slightly more noticeable on badly bumpy roads.
Steering is a lot crisper.
More importantly it may help prolong the life of expensive tires.

mishar

Formula 1 (and some other racing classes) is an ingenious concept. Great idea how to direct some easy many (cigarettes or lately energy drinks and mobile phones) into car development business and make excellent entertainment of it. Huge money and competitive spirit pushes it to overdevelopment at all times so it has to be regulated to limit it to some common sense. In spite of that that there are many things so advanced that it looks like they can never be applied to street legal cars. But if we look at car industry development we will find that almost everything came from racing cars. Not air-conditioning or entertainment systems, of course, but aerodynamics (cars use to create lift where down force is needed), brakes (carbon ones are here), gearboxes (pedal shifting), engines (turbo, materials, electronics) and so on, and so on. A8 looks like pretty distant cousin to Formula 1 car, but if we put TT, R8 and some Ferrari in between relationship becomes more obvious. In my opinion (not everybody’s) car has to be light, aerodynamic, safe, with lots of power, serious brakes, excellent handling, low center of gravity… I think that all this applies to street legal car as well as to Formula 1 car as close as possible.
Exactly what I meant.
Yet we keep trying to get there.
Agreed. Dinosaurs have just perfected their eating skills when environment changed. But there were others around. They became cheetahs and eagles later.
Nice. It’s never too late. Sometimes it goes from father to san. Sometimes the other way around.

mishar

Yesterday I aligned my wheels. Both fronts and rears were too closed. Guy (very experienced but not familiar with A8) Told me so before he even started, by just looking along both sides and touching tires. I didn't tell him that I found the same myself. Can't say that I feel any difference, but I hope tires will.