general problems of the 1999 Audi A4

Treads separated on both front left and front right tires along on inside edge of each while driving on interstate 93 in nh. One threw cord, the other showed separation upon examination. Dealer [lakes region Audi, gilford nh] checked inflation, at 31. 2 and 31. 4lb (recommended pressure is 32lb). Moderate tread wear (4/32in left?) after 30k mi. Dealer also performed re-alignment after new tires were installed, but found no serious problem (minor toe-in adj). This car is driven mostly in washington DC where it has been very hot recently, but these are temperature category a tires. Same failure on both front tires at same time suggests a possible manufacturing defect.