One problem related to tire sidewall has been reported for the 2004 Audi S4. The most recently reported issues are listed below.
Hankook tires, ventus s1 noble 2 splitting outside sidewall, caused to depressure tire, which caused to crack tire on the inner sidewall subsequently led to manufacturer claim blame on my vehicle. The tire model is under a recall, but in different size, but identical walls, manufacturing process. My vehicle's tire size 235/40/r18. Recalled: ventus s1 noble2 '245/45r18 96w', '245/40r19 94w', '275/35r19 96w proper tire pressure was maintained and checked weekly for 3years, since the vehicle was purchased.