I have two Conti Competition tires on my five year old race wheels. There is some slight separation of the black tread from the underlying casing which I believe is just due to age. It is near the sidewall of the rear tire. They still have plenty of tread but are showing signs of age. Is it too risky to use these tires? My next race is Donner Lake Tri with quite a descent and I starting thinking about a blow-out coming down the mountain pass.

They seem to be very tough tires with five layers of material but am I just being too cheap...should I just spring for the $90/piece to replace them? They don't leak at all and otherwise seem in good shape. Thanks!!