suspension specifications?

[george h]

I'll try to make this brief. Clunking noise when going over bumps, brought to dealer, who diagnosed broken right rear strut. OK, it's under warranty (35K) so I leave it and get it back a few days later with assurances that problem fixed. It's not fixed, and there is a REALLY bad shimmy in the right rear, way too much play in the up and down. They are only a little bit embarrassed when I bring it back, and today I hear that the problem is 90% fixed (they are bleeding the air from the suspension, as they understand from the service documentation that they didn't need to do that for replacing strut, but now it's quite clear that they should).

so the problem is "90%" fixed, and I say let me know when you have it 100% fixed, and by the way, what is the specification for suspension performance? They said (off the tops of their pointy little heads no doubt), there is no specification for that. And I want to know what you think about that.

sorry for the lack of detail. Ask other questions before you chime in, if you want. I'll be looking again soon. thanks for everything and this is a really great forum for the RS6 owner, I want to tell you all.

[S6LANA]

George, Are they exploring the possibility of a DRC issue going on? I hope it's not for your sake, but you may want to bring it up. DRC issues have plagued a small number of this model from day 1.

Good luck and let us know what happens. You're in the US, I presume?

[george h]

Yes, this car is at Princeton Audi, in NJ. I'll ask about a DRC issue. Is there another thread here to learn about that? I'll search here and see.

[Prince Ace]

This post is of keen interest for me too (though maybe not for the same problem).

I'm really sorry but I'm not mechanically minded at all and thats why I am at the COMPLETE MERCY of my mechanics !! :-( ..

Could you possibly briefly clarify / explain what you mean by a DRC issue ? I'm sorry if it seems like a silly question, but I simply don't know.

Thanks.

[bbigman2000]

The suspension on the RS6 is oil filled and its controlled by a bias valve centrally located at the rear, which controls the release of oil from side to side or front to back as cornering forces are sensed.

If you replace any shocker, you must replace the control valve and follow careful procedures to bleed the system.

Often its easier to replace the ENTIRE suspension and valve which is whats done mostly here in the UK.

My car has had the entire suspension system replaced, as have many others I know.

[george h]

From my reading here, it seems that the only specification is the system pressure (12-16 bar), but there is no overall spec for the "bounce" of the suspension. Maybe that's all well and good as they could be directly related. I see that it is up to me to determine whether I'm satisfied with the handling etc. For the record, my problem was diagnosed as a strut failure, not a shock failure. but they also said there was "leakage" of the suspension fluid. Is that a possibility if only the strut is involved, or are they misdescribing the problem?

[Prince Ace]

Good man bbigman2000. Thanks for that, much appreciated. :thumb:

[skiwi]

but they also said there was "leakage" of the suspension fluid. Is that a possibility if only the strut is involved, or are they misdescribing the problem?

there is no "strut" - in the rear of the rs6 you have double wishbones. i would request more detail, but, going on your description, i believe that the shock was the focus of their work...

[bbigman2000]

pleasure prince

strut is probably what the stealership were terming as a shocker.

[Minou]

If the DRC valve starts to fail it will inevitably cause a pressure problem in the shock absorbers/dampers/struts (all the same thing , just different terminology lets call it SDS) which will cause the SDS seals to fail and fluid to leak from them. The SDS leak is most likely therfore to be the symptom and not the fault. I had 3 or more months of this problem in Leicester in the UK with this problem so if I can help you let me know. I note that one of you is from the UK so i am happy to pass on my experience.

colin

[george h]

I retreived the car and it seems to be as tight as it was before. I have yet to speak directly with the tech to see what exactly was done and ask a few questions. But I take your point and will try to observe any changes in status over the next weeks.

[Aronis]

New detailed repair instructions have been sent world wide to Audi service centers. This was the result of a long list of owners having a problem with DRC leakage followed by very poor repair experience.

Now that the Technique for fixing it has been better detailed, they can fix it, and not a moment too soon as BRAND new RS4's have had the same problem.

If a Shock/Damper has been damaged it most like leaked fluid and thus that diagonal pair has been depressurized. The central valve linking that rear damaged shock with the one on the opposite front needs to be replaced, not because it is broken, but because they cannot In The Shop re-pressurize the central valve.

Glad it's back to your liking.... The one-diagonal pair soft drive is VERY strange feeling...for sure.

Mike

[george h]

Mike, yes, it was making me sea-sick. Do you know approximately when the new detailed repair instructions would have been sent? I'll need to verify that my guy got them, and if not, I'll want to know why they're not in the loop.

You say that they cannot re-pressurize the central valve, so any claim they make that they have done so is false. This is also useful information. Hate to say it, but I am a little suspicious of this shop and if they are pulling the wool over me, I want to catch them in it.

Thanks loads for the help everybody.

George

[Minou]

My understanding is that the DRC valves are pre-pressurised from the factory to 20 something bar and cannot be repressurised. Amongst the many efforts my Leicester dealer tried there was repressuring, bleeding them, changing various struts. It was never right in the end so I sold it. The main problem it seems to me is when the dealers have no one who can differentiate between handling and ride. After 6 months with a Subaru I now have Rs4 Avant (from a diffferent dealer) so I am ready for battle if the handling starts to deteriorate.

Find what they have done, do not accept anything less than 100% result, chase them to the top and do not be fobbed off. They are not cheap cars and they can be fixed. make the dealer contact the factory for the information.

When I was having my problems I was amazed to be told by Audi UK that unless the dealer directly said they had a problem and asked them for technical help they would not intervene. That was in spite of me - the customer - pointing out that December to March seemed to be a long time for them to be taking to repair my car.

colin

[skiwi]

i'm intersted in your impressions of the rs4 against the rs6?

[Aronis]

the standard starting pressure of the DRC central valve is 16 bar (according to Audi info - RS6 special training manual). 20 bar perhaps is that used in the newer version is the RS4? Not sure.

From a design standpoint, they could have designed the Central Valve to be repressurized by a screw rod or something to mechancially push the piston back to the 'starting' pressure...but no...

According to the techs working on my car (the regional service guy out of Marlboro Massachusetts) the shop does not have a compresser which can produce the 16 bar SAFELY.

16 bar is 232 psi. Pressurizing something with hydralic fluid to that pressure is dangerous.....thus the reason they have to bring in a New central valve.

The accepted range is 12 bar to 16 bar, which is a rather large range if you ask me...talk about a wide tolerance.

The design is poor in my opinion as the system lacks any "Easy" way to check the pressure without risking depressurizing it, if even a little. I would have thought that perhaps after hearing of leaking on the RS6 they would have designed a pressure transducer into the RS4 system that could give you an early warning of a loss of pressure.

From the cutaway drawing so of the central valve that I saw it seems that it could have been designed to be pressurized by using a threaded rod - to push the piston back to 'full pressure' as the 'pressure' is 'stored in the AIR chamber part of the central vavle. A hydraulic fluid by definition is ideally NOT compressible, but the AIR in the 'air chamber' is certainly compressible.

May be on version Three the DRC will be fixable at the Bench Top. Who knows....but if you have a 10 year old RS6 and the stock suspension Goes....finding new parts may not be easy!!!

Mike

[Minou]

I upgraded to the Rs6 from a S6 and inspite of my suspension problems that occurred when it was 30 months old it was great. I covered nearly 60,000 miles in it. I have had my Rs4 (all of them were Avants) for about 2 months and covered some 3,000 miles.
Suspension
The 4 rides as well but handles better, less understeer. The only track I took the 6 on was the Nurburgring (an annual event) and while it was quick it understeered too much to be fun, so after 2 laps I went back to my Lotus sunbeam. On the road the Rs4 feels much flatter and stuck to the road and less floaty than the Rs6. All these comments are relative, the Rs6 was much better than the S6.

Engine
I am nearly 60 and when I think of earlier quick cars that I have owned I am impressed how modern materials, electronic ignition and valve control etc can create an engine that has such a wide spread of power. It will pull 5 and 6 gear in town and still have good pick up. At the other end of the range at 6000 rpm it get second wind and spins to 8+ - amazing. It creates fabulous noise at all revs. Less low down torque than the Rs6 but that also had slight perceptable lag (torque converter masked it to a degree), so as good if not better than the Rs6 because it has a wider rev range,

Gearbox. 6 speed manual compared to 5 speed auto/tiptronic. I was quite happy with the auto, traffice jams it was great, less good if really pushing on. Nice manual box, light easy short shift. Clutch I am still getting used to. It has some widget in it to stop the clutch being damaged by slipping and this seems to result in a varied "bite" point. Fine from a standing start but I am still making occasional jerky changes in the 2 to 3 to 4 range. I need to concentrate and practice. Thought I might miss the auto but in fact it is not the case and it suits the car well.

Brakes too light on intial bite, for heel and toe down changes, on the Rs4. True but when braking hard and dropping down the box its OK, it is only when going gently and slowly that the problem arises and the honest answer is that I only do that for the engine noise. But ideally the initial bite would be heavier for my taste. Not really pushed the brakes yet but I feel they may be better than the Rs6. They could get hot and pedal feel would soften. They did not like hard use on a sprint circuit nor were they too happy by the end of a nurburgring lap.
Steering. Rs4 nicer with some feel to it and initial turn in is sharper, again less understeer.
Wind noise. The Rs4 is noisier, or mine is. I shall have a word with the dealers when I get round to it. Wind noise around the wing mirrors and my drivers door, which may well be door adjustment factor and there is a lot of tyre noise. 70-80 mph and one has to speak up. The Rs6 was much quieter. Any one else noticed this or is it my vehicle?
Fuel. This is the UK so I talk in terms of imperial miles to the gallon. The Rs4 uses less. Rs6 did 16-18 running around and 23-24 on long journeys using 70-80 on motorways. It did 6 lapping the Nurburgring. The Rs4 does 18-20 running around and 24-25 on motorways. Not much better but definately better. The smaller petrol tank is a pain.

In the Rs4 I have the sport seats which I find very good and locate me much better than the Rs6 recaros. However if you are fairly well built buttock wise it may be an idea to test the seats first as they do not seem to allow much width. The longest non stop journey I have done to date is 3 hours and find that the non adjustable head rest padding is pushing my head and neck forward a little too far so I may have to investigate opening up the trim and removing some foam.

I have not towed with the Rs4 yet, the Rs6 was awsome and I see no reason why it should not be as good.

Overall summary, the Rs6 was a champion but the Rs4 wins most rounds on points. Audi have raised the game again. Provided the new dealers I have gone to match the standard I shall be happy.

colin

[skiwi]

colin, excellent summary thanks.

i've gone ur-q 10v, ur-q 20v, rs2, s8 and now the rs6, with a couple of m-b's thrown in. this is by far the most complete drivers car i've owned, although the 20v would handle the twisties better, and had more ultimate feel. i have some track time in an rs4/s6/s8 tomorrow, hopefully enough to form a meaningful comparison, but i expect that with the rs4, i will find it just as you say.

the thing with the rs6 is that it is such a complete package, the extra room inside and boot space make it every bit as practical as the old s8. and the low-down mumbo with a good auto is the best compromise i can think of...

thanks

[george h]

update: the wallowing is not fixed yet. I am taking it back to the dealer Jan 2.

[LU-RS6]

The smaller petrol tank is a pain.
That would be the one thing stopping me from buying an RS4.
82 liter petrol tank in the RS6 is a HUGE advantage for people also driving longer distances with these kind of cars.

[quick500]

I have noticed my rear shocks are leaking and the rear of the car twictches would i be able to replace the two shocks and have the system re-oiled?

[Aronis]

rear shocks are connected to the front shocks.

Rear Passenger to Front Driver's side and vice versa.

So if the rears leak, the central valves empty and the front leak out via the central valve.

So the process involves FINDING the leaking points (now in a system which is no longer pressurized), find any OTHER leaks that are possible...same seals in the front leak for the SAME reason as the rear seals.
Once ALL leaks are fixed, refill shocks and tubing, then connect to NEW central valves which are factory fresh and pressurized.

Mike

[george h]

in other words, Mike, odds are low that an unexperienced mechanic will be able to remedy the problem. I am afraid this will take me the best part of 2007 to fix, fighting every step of the way. Do I need to get AoA on my side right now? Probably. Just great. I hope I am not too busy to get this done the right way. If I don't do it now, the car will never be right!

[Aronis]

There is are large experience fixing this problem. After several of us went through this repair and all bitched at AOA about the lack of sharing information, it appears that a new DRC repair buletten has been sent to all dealers.

The process involves a basic understanding of hydraulics and a tech who can follow the instructions closely.

The flaw in the repair is the lack of the understanding of why they leak. The galvanic action between the dissimilar metals it he cause. The SEAL is an allluminum ring and the fittings are steel. STEEL-ALLUMINUM-STEEL This causes corrosion and the ALUMINUM ring breaks down to powder....thus the leak. In most reported hear the problem first shows up as a leak in the REAR...

They would NOT listen to the logic that if the rear seals have leaked then the fronts would also. They replaced the rear shocks/SEALS/ and reconnected to new central valves. The fronts now being exposed to full pressure once again, then LEAKED.....resulting in a very loose front end....Finally they changed the FRONT SHOCKS/SEALS.....and with the last set (third if I recall) of control vavles my car was back to nearly normal (not quite as firm as new) but very good just the same.

So if your guys get FOUR SHOCKS and TWO CENTRAL VALVES (right and left) and do it all right, it can be fixed in ONE DAY. PERIOD. ONE DAY......

Mike