FYI, do you know how many layers and how thick the tires for the so call minor cracks to impact overall safety? If only minor cracks on the surface there is nothing to worry about, unless you can see steel wire visible thru the cracks than is better to change it.

Do go and join drifting/touge class you will know why we can come out this. Most drifter use 2nd hand tires for training and drive until steel wire come out, creating all the sparks then only burst so that is the limit.