briguyD4A84.0

Is there a way to upgrade the rear sway bar in the D4 A8? Perhaps a way to make it stronger or larger in diameter or stiffer in material? I have heard there is a way to do that with the D3 A8, and was wondering if there is anything like that for the D4 A8. I may have posted this in the wrong place before, pardon. I was hoping someone could point me in the right direction. I have an A8L 2013 4.0, and live in Florida.

Best
briguyd4a84.0

Minimarvel

MP4.2+6.0

If it follows D3 where I did the mod, then the upgrade path is probably the S8 bar set for a 4.0T A8. You should look at EKTA parts diagrams to sort the available choices. On the D3 there were three levels--standard, sport and S8.

LexusLSguy

I am also interested in this upgrade. I have upgraded the rear sway bars on other vehicles in the past and it makes a big difference.

Stevereddy

Count me in as interested......if there is an upgrade for flatter, more neutral cornering for the D4 I would like to know about it. Is the S8 bar or links different than the A8 bars?

MP4.2+6.0

Since I have an S8, I'll leave to others to do the research down to part number specifics for what you want. Looks like bar is <$200 via online discounted dealer. Better approach perhaps--just call your dealer parts dept. of choice, give them your VIN and ask what your car has stock. Then tell them you want the S8 [whichever parts] and have them pull the current part numbers w/ pricing.

Having actually done the sway bar mods on my two most recent prior Audi's I was still curious enough to poke at it more at the parts level. Various conclusions I reached from what I saw glancing through the EKTA slides--and having done the mod on my D3 A8 W12:

1. For rear bar, it turns out there are only two levels of bars: the standard basic one, and then the beefier one. Unlike D3 though where they have a distinct S8 bar in the back, it looks what they would call the S8 suspension and the sport suspension on a D4 both use the same rear bar. Here's where I don't know the nuances on a D4 A8 of whether there is a sport and non-sport flavor, or maybe it bundles in with the upgraded rear diff or some such.
2. If you look at your build sticker (or get parts guy to check by VIN), you will be able to confirm which set up you have if you don't already know. A 2MB is the code (a "PR" code) for the S8 set up. A 2MA is what at least on D3 was called the sport suspension. A 1BK or 1BY will be the non-sport default. 2MA and 2MB both already have the beefier "S8 level" bar in back.
3. Rear bar link is the same regardless of suspension version.
4. Rear and front air strut units are three distinct flavors depending on which set up/PR code.
5. Rear bar apparently does the stiffening the typical old fashioned way--thicker bar, presumably solid. That was the D3 set up too. Basic bar is 19.6mm; heavier bar is 21.7mm. In cross sections small diameter changes make big overall differences if you work the math. Front bar BTW is probably tubular like D3 was, so there the bar diameter may be the same but the wall thickness varies depending on which version it is.
6. From having done the rear bar on the D3, this is not a simple job compared to the front, though not as hard as ones that basically require a rear subframe drop like Mini's. If like D3, I documented a way to thread it carefully in from one side of the car (with wheels off). It was definitely not what shop manual said--which was the usual overdone, step 1 drop huge assembly stuff, and then hours later go to step 2, and by the way have full shop equipment, lift, etc. I had to loosen one suspension arm (just bolts but an adjustment point so it had to be marked for position). I also had to undo exhaust hangers and pry it down some in the back. By contrast front bar is really simple access and basically just turn a handful of bolts.
7. In front just as an FYI, there are no differences shown for any of upper or lower control arms or the sway bar links ("coupling rod" in D4 EKTA speak). I checked since on D3 the upper arms did use a different inner bushing at part # level for the S8's.
8. In front, there are three distinct bars. These also have color codes painted on them. Supposedly white is the base one, orange would be sport suspension level (or W12 non sport), and yellow would be S8 or W12 sport. Problem is...my factory equipped 2015 S8 has the orange color bar, not yellow. Thus a caution that even supposedly official Audi EKTA can get this stuff wrong. See pic below. I took a bunch of these shots when I first bought car, and happened to find one showing it. Looks like you can see the paint coding looking in from USA driver's side.

Having waded thorough all this, I guess maybe one caution I can think of that goes down the path of "this ain't your father's Oldsmobile," or rather Audi 5000 or early A6 quattro. Presumably the reason folks are interested in the rear bar is the usual rule of thumb tuner idea--stiffer rear bar can pull out understeer, especially on a FWD biased or legacy platform...like many Audi's. But not clear to me if that is really still D4, at least some flavors. Thus, even compared to my D3 W12 or my 2000 C5 4.2, both of those were 50:50 Quattro, not 60:40 like first came out on D3 S8 and now pretty common Audi, at least on the more powerful ones. Further, and maybe even to the point of caution, I would be careful if you have the package with the sports diff--like S8's as standard. There I would speculate there was some factory thought in the specific set up, and the bars and air struts were likely all designed, tuned and controlled as a package.

Maybe more generally from having done the bar change on D3 W12 both front and rear: There the D3 W12 used sport bars even though it was a non sport air ride. Probably had to do with the greater weight. I went to S8 bars front and rear, as in "one level" above my car's stock set up. What I was after there was basically a tighter general feel and slightly stiffer ride, even though it had 35 series factory 20's. I got what I was after, and enjoyed for better part of 100K. It was sort of similar overall to when I have used the Bilstein B6 struts on Audis with conventional set ups instead of the factory type B4 comfort ones. Thus, a notch up, but not way stiff either.

Minimarvel

Sorry for my previous short reply....To confirm...

2015 A8 D4 3.0tdi.
First played with suspension heights....horrid ride at a lower setting and worse the ACC cruise etc errored.
I found the chassis number of a 2015 S8 and ordered the front Anti roll bar and fitted it (Orange) . Strange outcome as seemed front of car firmer but rear of car still floating.
Original front bar weighed 3.7 KG new bar weighed 4.0 KG otherwise looked identical with orange paint mark.
Ordered the rear Anti roll bar. New one much thicker at 21.7mm. Fitting was not a major issue. Dropped exhaust back boxes to get a bit more clearance 30 minute job.
The car is transformed....!

I sold my 2009 S8 and bought the 2015 A8 hence it was quite a shock to drive something with suspension so soft.

Ride now is the same but car now corners flat. Steering MUCH more responsive. Noise level about the same.

LexusLSguy

You tend to loose a little comfort but the gains are well worth it. When I upgraded other vehicles it improves as exactly stated. Swaying motion is notable reduced to produce better tracking and less swaying at high speeds in the wind. This is probably the best part. Makes the car feel more planted. Of course improved cornering. For instance the STI rear sway bar fits on the Subaru Outback. The rear tends to make the most difference. Did you also do the bushings? Can you post a link to the part? I'm probably only going to do the rear.

Edit:
Is this what you ordered?
https://parts.audiusa.com/p/Audi_201...H0511305E.html

MP4.2+6.0

FYI, on rear you have to do the bushings in any case given the greater bar diameter. The C shaped brackets holding them are likely the same.

Stevereddy

Thanks MP4.2+6.0........your technical knowledge is greatly appreciated. I am going to order sway bar and bushings and do this install in conjunction with the rear exhaust work on my A8. I know the A8 is not a popular car to mod but I never wanted an S6 or S7, I like big body cars and that’s all there is to it!
I think with the Apr tune I have on it along with sway bar in rear and some light weight alloys with sticky rubber this summer it will be perfect.
My goals always were 1. More power, 2. Better handling, 3. A little more exhaust noise......what can I say, I am a hot rodder from way back!