Age is now becoming a very serious issue. I have a 1985 Cadillac Convertible, I purchased new when I was 25. In the last 20 years the car has traveled only 3000 miles. It's has had four sets of Vogue Tires in that time. When I have the "Wire /Rims" tuned, the wheel tuning company, requires the tires be less that 5 years old, or they refused to remount them. I keep weight off them and they are covered and garaged. It's the breakdown of the materials. I usually put them on Craisglist and someone buys them. I have a release they sign. It's kind of sad, tires look new, but tis a fact they can fail.
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