The 17-year-old spare tire is smaller than the road tires, and doesn't appear to hold air. It's now at its maximum pressure (55psi). So are the road tires, but they're only rated for 35psi.
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DOT, Ford, and most tire manufacturers say that a tire is risky after 6 years (regardless how many miles it has been driven, or its tread depth, or even if it was never mounted), and dangerous after 8.
The 2-year-old road tires have not been driven enough since their last rotation to assess their wear patterns, but they are at their maximum pressure (35psi) and have plenty of tread depth.