gaspasser19

So, you were hell bent on getting tires with shorter sidewalls then you went with a tire that has a taller sidewall than you had before? I'm confused.

hunterp27

Well I was hellbent on it but I kept getting too many negative responses from individuals ranging from it being dangerous to messing with the computer. If all of these things are just people explaining the potential pitfalls at the far edge of likelihood, then I would reconsider it because i think it will make it look better. I truly think the ride degradation would be nominal and within acceptable limits to me. What I fear more than anything is setting off alarm codes with the computer. So, don't be confused.........its really what I want to do but don't need the headache of chasing codes. Are you considering the same thing?
Hunter

hunterp27

Also Gaspasser,

On paper the 275/35/20's would appear to be have a higher sidewall than the 265/35/20's that came as the OEM tread. However, after doing some deeper investigation, almost all-if not all 275/35/20's are not as wide as the stock Yoko's that are labeled as 265's. The actual tread width and cross section of the Yoko's has actual measurements that are wider than the 275's I am looking at. So, with that being the case, the sidewalls of the 275/35/20's is actually shorter than the stock tires.

[QUOTE then you went with a tire that has a taller sidewall than you had before? I'm confused.[/QUOTE]

dvs_dave

I would disagree with that. Lower profile tyres transmit more shock and movement into the suspension system which makes it work harder, and by default wears it out quicker. It would be interesting to see if any data has been compiled around this but I'd put money on cars with lower profile tyres having a greater likelihood of suspension problems.

MP4.2+6.0

Just look at the tire spec's for any of the models, such as the Yoko. The S8 tires are all right around 27.3" in static diameter. Obviously the metal rim is fixed, so the delta is exactly twice the sidewall height. The 275/35's found on many W12's and on some of the later 20" 4.2 sport versions are 27.7" in static diameter typically.

Thus, the actual sidewall is not some locked in measurement based on the field tread width per se. In fact it's more the tread width that varies some within a given tire size, and not the sidewall height. Said another way, the old calculation of 2x tire width x aspect ratio + wheel diameter = tire diameter is only a general approximation, and it's the tread width (and the overlapping sidewall to sidewall measurement that goes into the bulge/non bulge look) that is typically the more inconsistent element

MP4.2+6.0

The car has no real way of knowing the tires you put on electronically. What it will throw up on are materially varying tire diameters on one axle or the other--the running circumferences should all be close to the same. I'm not sure that will actually set off a code or maybe get ABS or ESP confused, though it seems plausible. People generally know it is a no-no with AWD/4WD anyway so it doesn't get tested much. The speedo also gets thrown off when the tire size varies off spec, but there is no news there compared to any other car either--and no, it can't be recalibrated via VAG COM. As I mentioned earlier, the 20" A8 stock tire diameter seems like the very close to ideal one to minimize speedo error, at least on my W12.

On the D3 even the factory has three basic diameters: 27.0" used on the 18 and 19" wheels, 27.3" used on the S8, and 27.7" used on the 4.2 and 6.0 A8's. All co exist fine on the D3 platform, and you don't reset any electronics as among them. I even ran the 18's with stock 255/45's on my W12 for about 1000 miles while getting my wheels refinished a year or two after I bought the car. Zero issues sensor wise or electronically, though a big performance let down as between the two tire fitments involved. Guys have also been running the D4 tire size at times with 20" OE wheels they got for their D3; that is typically a 265/40, which adds about another inch tire diameter wise IIRC. Again, no reported issues.

I stand by what I said though on the loading and too little sidewall at 30's. Maybe not everyday on a nice smooth road, but a big pothole or a raised railroad track or even a sharp driveway edge will not be your friend. Just takes one good hit, and again w/ an S8 you are riding on cast not forged Audi OE 20's. Bubbled side walls are pisser's, but bent wheels a major downer. FWIW, those few doing the 30's are usually going up another size or so, like 285/30. But then they are effectively "growing" the sidewall again back toward the stock height.

Be sure too you are looking at real world math of probably 4600 pounds of Audi pork in a U.S. spec. S8, maybe 1,000 pounds of possible passenger weight (for 5 full sized adults), and what ever for the trunk load--regardless of what the sticker says. Also remember it isn't just weight divided by 4 to get to each wheel. Approximately 60% of the total weight is on the front's, with a slightly greater percentage for either the heavier motor S8 or W12. Thus, it's the front math that matters, unless you fill the trunk with cement that is. I actually haven't seen/recall a precise spec on this from Audi (which BMW and Merc. like to position against), but the 60/40 type range should be close enough and is in the zone of typical Audi AWD (FWD being a few points worse). And yes, at a technical level as I said before, there are nuances to an S8 too, like extraordinarily heavy unsprung 39 pound front rotors (each) up front, close to 20 pounds of brake caliper related stuff, the heavier non-forged wheels, etc.

MP4.2+6.0

they specifically had their website programmed to object to choosing an XL rated tire for the W12 because it might be "noisy" or "rougher." To me that's insanity--specifically overriding the manufacturer's spec. that was done in the first place for safety. I'm sure they have people somewhere who have better knowledge, but the web programmers evidentially weren't among them. I actually called them about it, and they essentially blew me off and stuck with the company party line of why they were trying to "help" the customer. The Ford Explorer rollover fiasco is the poster child for why this stuff needs to be taken very seriously--overloaded vehicles with underrated tires, admittedly coupled with probably lack of owner vehicle attention in many cases. Not a good customer experience, and when grounded in safety issues I take it seriously.

More generally, I still have to question overriding the manufacturer's stated weight spec., whether XL or the specific weight class--97, 98, 99, 102, etc. I would not do that myself, and a few times walked away from tire choices (like the first generation Michelin Pilot A/S's) before they rev'ed them in the next upgrade.

On your tire choices, I ran the predecessor to the current SuperSport on my A8. Nice tire, and even better regarded in its current iteration. Like the Dunlop Sport Maxx's I ran before and since, it's a low 20K mile tire. I ended up back on the Dunlops when I bought a later set of take off's OE's shod with them already mounted. Having run those two alternating for about 2 ½ sets of life now, I can't fault the Michelin--which I have run in the prior and current form on the family Mini S too. But FWIW, I honestly couldn't find a real difference on the D3 platform--with another high performance engine--as between the SportMaxx's and the Michelins'. But the Sport Maxx's were in a lower price bracket.

If I chose new today, I would end up with the AS3's (or Dunlops if I stuck to dedicated summers and also took some $ out). I get there given the reviews all say pretty close to sport performance with the AS3's but with somewhat better life, similar price point, and marginally more forgiving ride. I do some transition season snow use though which you may not, so A/S may not matter. If you are in freezing weather though even w/ out snow, it still can relative to a pure summer choice. Summers on sub 40 degree even dry pavement are not the best.

Gzila850

Replaced P Zero Nero 102y 275/35/20 on my W12 over the weekend. Had expected to go with Michelin PSS AS3 but my tire guy steered me too Nitto Motivo's. 60,000 warranty! First impression is very positive. Quieter than the Pirelli, stiffer sidewall and the car just feels "better". The Pirelli's were at the end of their life so ride quality was suffering.

hunterp27

Well, after all the back and forth, gnashing of teeth and wringing of hands, I finally settled on new tires...........and...........I chickened out and went back to the original OEM sizing of 265/35/20. I seriously considered widening the tread to 275 and shortening the sidewall to 30 series, but kept running up against sidewall load ratings that didn't meet Audi's spec. Admittedly it was close (97 versus 99) and certainly all of the tires I was considering are likely over-engineered and this wouldn't be an issue, but in the end, peace of mind trumped my desire to lower the sidewall profile. Additionally, I didn't want to have to guess at speedo re-calibrations or potentially mess with any on-board systems such as suspension or ABS or anything else. Granted, all of these worries were likely unfounded but I simply didn't have it in me to chance it....... Anyway, with that being the case I decided to shuck the Yokohama's and buy Michelin Super Sports. They are on a truck headed to my house and I will get them mounted and do a 4-wheel alignment before putting any miles on them. I will report back afterwards and give my review to the forum. My hope is that things quieten down and this big beast stops tramming on every inconsistency in the road.
Hunter

hunterp27

The new Pilot Super Sports are on my S8 and I couldn't be happier. Extremely quite, huge dry grip and it started raining an hour after getting it outta the tire shop. Wet traction was far superior to the Advans. Yes they were old and worn but it just seems to be a far better tire. I would endorse these to anyone who wants to spend the extra money.