Google is my friend and led me to the Michelin RV Tire Maintenance Guide . It's a .pdf file that I downloaded. The guide talks about tire cracks on page 7 of the guide.
There is a picture in the guide that looks just like my tires. The guide says that if the cracks are less that 2/32 of an inch, the tire is okay to use. My tires are just slightly cracked, I can barely get the end of a toothpick in them, so I'm good to go. I will keep a close eye on them and I will purchase some tire covers to protect them from sunlight when the Journey is parked.
Just one more thing to keep an eye on.
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