"Worried" is a broad term. I used to read the side of the bias ply tires to see how many plies it had so I knew when I was down to the last two so I would know when to start shopping for some "new" used tires. (Running down to the very last ply would have been reckless.) I am not recommending that particular method to anyone, but I used to be po (couldn't even afford the other "o" nor the "r").
Carl
