Guys on the D3 Forum have been using VAG to lower their cars about 3/4 of an inch and are running into road clearance issues. There have also been complaints that the speedometers are 5% optimistic. So, I was wondering if a tire with a 1 inch greater diameter would 'give back' a half inch of ride height and cut the speedo error at the same time? What am I missing? Some '04-'05 Phaeton owners (Mr.Ricco) may also be interested. That car has a huge tire to fender lip gap! They are raised 1/2 inch higher than the euro Phaetons - because they have better roads in Germany!

The 255/40-19 has a 27" diameter. The 255/35-19 has a 26" diameter, which would increase fender gap by 1/2" and reduce the 5% speedo error to 1.3% optimistic. But there is one potential safety issue ...

Using <a href="http://www.tirerack.com/a.jsp?a=AR4&url=%2Ftires%2FSpec.jsp%3Fmake%3DPirelli%26model%3 DPZero%2BRosso%2BAsimmetrico">Pirelli PZero Rosso Specs</a> as an example, the <a href="http://www.tirerack.com/a.jsp?a=AR4&url=%2Ftires%2Ftiretech%2Fgeneral%2Fspeed.jsp">Load Index</a> of the 255/35-19 is 92 versus either 96 or 100 for the 255/40-19. Using the worst case, this is a big 375 lb or 21% reduction in load capacity per tire of a very heavy car. You can compensate somewhat by running <a href="http://www.tirerack.com/a.jsp?a=AR4&url=%2Ftires%2Ftiretech%2Ftirespecskey.jsp%23maxlo ad">Higher Tire Pressures</a>, but higher pressures combined with a 3.5" sidewall will result in a very stiff ride.

What load index is stamped on the OE D3 A8 tire? Because of the potential liability, many tires stores will no longer even mount a tire with a lower load index than the OE tire.<ul><li><a href="http://www.audipages.com/upgrades/tiresizeoptions.html">audipages A8/S8 tire options</a></li></ul>

So a higher load factor means Less weight capacity... Am I understanding that correctly? Your tire chart doesn't show load factors. Something I'll need to research. That can be a problem especially with an A8L - worse on a VW Phaeton. Sounds risky, but so is hitting curbs and parking dividers due to lowering.

255/35-19 .... 92 load index ... 630 lb capacity
255/40-19 .. 100 load index ... 800 kg capacity<ul><li><a href="http://www.tirerack.com/a.jsp?a=AR4&amp;url=%2Ftires%2Ftiretech%2Fgeneral%2Fsp eed.jsp">Load Index</a></li></ul>

The 255/40-19 has a 27" diameter. The 255/35-19 has a 26" diameter, which would increase fender gap by 1/2" and reduce the 5% speedo error to 1.3% optimistic.

The Load Index of the 26" diameter PZero is 255/35-19 is 92.

The Load Index of the 27" diameter PZero is 255/40-19 is 96 or 100.

&lt;&lt;&lt;&lt;&lt;This is a big 375 lb or 21% reduction in load capacity per tire.&gt;&gt;&gt;&gt;&gt;?????

Isn't the above statement reversed? The larger OD tire has a higher load rating - a 21% increase in load capacity...

an "H" speed rating for 18" or 19" wheel. Don't think they make such a beast!

The cosmetic result desired would be attained as follows:

The stock A8 or Phaeton tire is 18 inch and 27 inch diameter...

Lower the car 1/2 inch on the suspension, using the VAG tool.

Increase the tire OD 1 inch to raise the car back up 1/2 inch to compensate for the ride height reduction due to the decrease in suspension height. (Perhaps increase wheel size to 19 or 20 inches.)

Final result is a 1 inch reduction in tire to fender gap while maintaining road clearance under the car. Speedometer should be more accurate. Gas mileage should improve a little. Acceleration should decrease a tad. Should look terrific!