I have always run 38 PSI all around for years on my 20's (275/35X20), receive a comfortable ride, excellent handling
and great mileage.

 

Same config as above, 9jX20 with Dunlop SP Sport Maxx GT 275/35/20. I have 41 PSI on front and 38 PSI on rear. Sterring feels a little funny when the road is uneven like pulling the wheel of hand. Tires are brand new, wheels have no error and they are aligned correctly. That's definitely something wrong with front PSI. Will go a little lower maybe 39-38 PSI and get back with news.

 

No help there. All performance summer tires are doing that.

 

Does car track straight on normal pavement? Does it feel different when just starting out and tires are cold, as compared to when you have been on the road for a while and they are warmed up (assuming decent weather)?

Does steering shimmy at all during regular driving? Does it shimmy on braking?

Tires are new as in a just few miles/km or put on in last week, or relatively new but with some months of driving?

How many miles/km on the car? And, has it had any front suspension work done?

Meanwhile, w/ a few more years of running since prior posts and with both A/S and winter tire experience now with car, I am moving to about 39PSI front and 37 rear--that's down a bit from before. I am seeing slightly more wear in centers of tires than on shoulders, and more so in rear than in front actually. Has nothing to do with ride or handling. FYI, I previously ran a set of 275 Sport Maxx's (the older/original tread pattern that is for these Dunlops) as well as Michelin PS2's. Both sets ran well and to their full life. I would use the same tire pressure settings with those now too from what I have seen when I run the tires all the way from new to full life. Only now am I realizing more the difference in wear from front to back on the W12, since usually the tires get rotated front to back w/ seasons or otherwise before I see the wear across the tread and know tire was at the same axle.

Note for others: these PSI's are W12 specific; different pressures apparently apply to 4.2's (even with similar optional 20's and 275s) per the factory tire pressure stickers.

 

Alright i will get them in order as you asked many questions.

Does car track straight on normal pavement? => Yes.

Does it feel different when just starting out and tires are cold, as compared to when you have been on the road for a while and they are warmed up (assuming decent weather)? => Can't say much here cause i only drove it just a little. Outside temperature 17 degrees Celsius.

Does steering shimmy at all during regular driving? => Not at all.

Does it shimmy on braking? => Same as above.

Tires are new as in a just few miles/km or put on in last week, or relatively new but with some months of driving? => Tires were put on yesterday, brand new, professionally balanced, inflated with nitrogen and drove it under 50 miles since then.

How many miles/km on the car? => 106k miles.

And, has it had any front suspension work done? => Not recently, last service entrance was at 100k miles with no suspension repairs. I know exactly car has no suspension issues. I am a bit obsessed with suspension, brakes and keep checking constantly even without reason.

 

Again, I ran Dunlop SportMaxx's on mine in 275's. I ran them from when they were newly installed on the CPO car I bought at 16K miles for the next 22-24K miles. No issues of note on road. Removed them to run Michelin PS2's next, also summers. Having now run both, I would go back to Dunlops relative to PS2's. Dunlop performance was similar wet or dry, they were very slightly quieter, and cost a fair amount less. PS2's have since become the PS Sports though. In both cases, as summer tires they would feel a bit rougher when cold; just for a mile or two. Summers often "flat spot" when parked overnight and noticable when first starting out. And yes, car can pull a bit if I get into a pavement seam, but so does my A6 with 255's in summers, and I've even had that with tires down to like 205's on much more pedestrian vehicles. Just a little more obvious as tires get bigger and with mostly lengthwise tread patterns.

Ideas:

(throwing out possibility of a bad tire)

1. Cut the PSI back to 39 front (or even a bit less), 36-37 rear.

2. Even if you are particular on suspension maintenance, look carefully at front upper control arms. Now a pretty well known Audi weakness among the heavier platforms (including D3's) ever since they went to the aluminum front suspension in later 90's. At your miles, if they were actually never done before they are likely worn/somewhat torn out at the inside bushing. It is hard to see unless you have a wheel corner at least jacked up, and still not that easy without the wheel off. That part may "rest" a certain way for standard alignment and such, but can move more under loads and shift the running suspension alignment some. If you had said yes to the shimmy questions or had odd tire wear, it might have been more evident, but still the cumulative miles suggest taking a close look. Tie rod ends (especially the unseen inners) at those miles might be another area. Again from your info, there isn't anything obvious here, so this is just to eliminate one of the few possibilities besides normal road imperfections.

After that, it comes down to living with it as a consequence of wider tires and tread patterns. It may also improve if you see somewhat warmer outside temps than 17C.

 

Many thanks for quick reply! I would give it more time to run and higher temperature to come and see how it goes. And alignment or geometry whatever calls it has been also done same time when i put the tires on and results are all 4 green without modifying anything. With the previous winter tires 235/50/18 noise was lesser and way easier to drive. To be honest apart from the image i don't see anything better with 20" than the standard 255/40/19 as factory fitted.

I have also weigh the tire and wheel before mount and results are:

9J X 20 rim - 15kg
275/35/20 tire - 13kg

Almost 120kg total for 4 wheels i think is a lot even for an Audi A8.

 

On my W12 with all seasons I run 41 psi all around. 275/35 tires. I noticed that the outside of the tires were wearing more than the inner.

 

On the front it needs a bit more PSI to deal with the cornering scrub off. As the suspension wears it will tend to eat those edges somewhat more too. But, had enough experience now with the W12 rears (and specific to the 275/35-20s) to definitely say back the PSI off there by several pounds compared to front. That was not my C5 4.2 experience, but I can see more center wear in back--a surprising amount compared to all my other Audis over the years--if I hold the rear pressure the same as the fronts. Just caught it on the (new) snows as I put those away for the season, and saw it on my most recent Michelin A/S's last fall as they came off.

 

When I get new tires I am going to check the control arm bushings condition beforehand and get a 4-wheel alignment regardless. So you suggest 40psi up front 38 rear?