My M3 spare has been sitting untouched in the trunk for almost 5 years, and my road tires are almost ready for replacement (I drive about 4500 miles yearly). I want to use the spare and replace it with one of my used tires. I have heard that the rubber "hardens" over time. Can I use it? Should I try to buy another unused spare (235-40 Pilot) of about the same age so they are "matched"?