jlbell

Mine make the same sound when it is below 30 degrees Fahrenheit. It stays around until the car has warmed up.

Greg5OH

^ yes today it is over freezing and the car has not made that sound!
but still...i need to find what it is..I dont like it, very unluxurious...

the_duke

My D4 makes a noise over speed bumps when it's cold. D3 did it too. Audi has a TSB stating that it's normal when the air bags are cold.

dvs_dave

Not trying to justify anything. Just there's more to it than simply "make the bushing bigger". After 2 decades do you not think Audi have thought of that?

Specifying suspension bushings is an exercise in compromise. Its not like other luxury sedans don't suffer from similar suspension bushing life (50k miles isn't short lived in my opinion, but there you go). A cursory google across the BMW, Mercedes, and Jaguar forums will attest to that.

Greg5OH

indeed those bushings if were to be made bigger, could also impact steering feel heavily as they deflect in 3 dimensions to confirm to the knuckles rotation.
still, a peculiar design.

dvs_dave

Here's a good animation of it in action. (It's an A4 but A8 us same design)

http://www.audi-technology-portal.de/video/257

mishar

Actually it is as simple as "make the bushing bigger". Very good example are lower arm bushings. Same 3D movement under much more stress and they last vitally forever. Another one is A4. Again same movement under a bit less stress and they last.

I don't know if they where thinking of that, but I know that they should. It is not just about squeaky sound. Even before they start to squeak they change alignment and ruin tires, handling, braking, acceleration. It is unsafe.

dvs_dave

You're missing my point. If all they want to do is make them last longer then yes, make them bigger. But that will come at the expense of NVH, suspension geometry alterations, steering feel, durability of other components, whatever other attribute, which presumably has been deemed too much of a compromise. I really don't think Audi engineers have not considered and tested what a bunch of armchair experts on the internet opine.

True answer is a new suspension design all together, but that will have its weaknesses also. At least with the current design it's overall pretty solid, with only the upper control arm bushings being a known wear and tear item that's good for 50k miles and a cheap and easy fix.

Check out Jaguar XJ rear suspension bushing replacement cost for a reality check.

mishar

You are right. I am missing your point. You are saying that all might go wrong if there are a bit bigger bushings. Do you think they even tried bigger bushings? Or they relied only on stress analyses? If that, how does it tell about steering feel?

MP4.2+6.0

FWIW, yes I do actually think the engineers are out to lunch on this, and have been for ages. Or maybe better said, not even deployed on it. Among other things, rafts of them--and their leadership team unless you believe the laughable "Schultz" defense--have been too busy figuring out how to cheat on tests...and now probably feverishly redeployed to autonomous and electromobiles. Chassis engineers? Probably too busy figuring out the next shelf/brand expansion plan for this month's intro than to do the necessary unsexy sustaining engineering.

But, those opinions/spins aside, yes I think this part of the platform has been neglected for ages. The key parts of the equation they didn't think through that have changed in the 20 years since the A4 design was done that locked all this in are a combination of both the horsepower wars and the design wars. On HP wars, the torque and braking forces that get fed through these bushings have basically doubled, just assuming similar speeds over time and miles. And the unsprung weights have gone way up too, as have the overall vehicle weights. An Audi wheel (w/tire) of the era when the design was done was in the low to mid 40 pound range, and rarely pushed 50. Not sure if I could find a sub 50 pound Audi audi wheel any more, other than a donut spare or maybe on a tt stripper. On our cars they are high 50's into the 60's. Then add to it the front brake rotor that has gone from 20ish pounds in the design decision era (and maybe mid 20's for larger ones back then) at well under 300mm, now up into 30's and even pushing 40 pounds on the W12/S8. Caliper sized way up too, even with shifts from cast iron to alloy type designs to offset some of that size increase. Ridiculous pork weight that sells in the market--mine's bigger marketing when you strip off a lot of the veneer. And that's marketing over engineering when it pushes through sub systems like these, not engineering based designs to support them. Add to it, the vehicles that get sold here in North America are typically the high horsepower ones, while in their core EU markets they are often a lower power design and sized down supporting components like brakes.

Yeah, Audi could and should have done a lot better here in my book. It is literally the weakest design spot in the platform (or maybe tied with the Rube Goldberg trunk umpteen attempts to bandaid). Front suspension seems like it will go down the same way on the D4 from the early reports from the arm and sway bar link dead canaries. But do they care? Sales up, and focus primarily on new vehicles and feel good JD power type market spin satisfaction numbers. I'm not even sure they are that cognizant of an issue, let alone care. Now with the combination of the utter debacle of TDI and catch up play on both electric and autonomous, engineering and top leadership is most focused elsewhere. In the unsexy world of suspension underpinnings, most platform resources you hear about seemingly going mostly to standardizing them (MLB platform for the longitudinal ones), which then can leave a heavy and powerful high end side of the product mix left with the same undersized component conundrum...20 years on. And even if they have some resources, they way earlier go to things that sell--like user/MMI adjustable tuning ("Drive Select") they can get more $ for on all the trickle down deployments below the D series.