Thank you very informative, thanks for taking the time to write this.AO stands for Audi Option. (MO Mercedes, N Porsche, K Ferrari...see list in link below) It means that the tyre has gone through a testing process by the car manufacturer in a number of categories. In some cases the tyres may be exactly the same as the non-homologated versions, in some cases they are not e.g. the older RO1 tyres for the Gen1 had a narrower shoulder. There are normally only two or three tyres approved for each size, e.g. on the gen2 20" tyres the following are approved :- PZero (the newer PZ4), Michelin PS4S and Michelin PSC2.
Personally I think the homologation process is of more value to the tyre manufacturer than the customer, but I'm open to others opinions. I have a C class which had MO approved PZeros fitted as standard - they were the worst tyre I have ever owned - extremely hard riding, poor life and I had a catastrophic failure of a front tyre at less than 9,000 miles. Similarly the PZeros on my gen1 were very brittle after just over 3 years and there was such a difference in every performance category when I changed them out to non-Audi approved Goodyear Eagle F1s.
Does anybody really believe that Audi does extensive tires testing on all the different tires for each model car. its all $$$ This is company that does its own emissions software !!!!I think AO means that Audi get ££ for every tyre sold and the tyre manufacturers sell more tyres. Only my theory!