Hmmmm ......
How come #1 my 1995 ungaraged out-in-the-sun pickup goes 10-15 years before it's tires' treads wear out and the tires' sidewalls are still pristine and crack/check-free (just dirty)? (No covering of it's tires, no chemical treatment of the sidewalls of it's tires, and sometimes driven a couple times a month and sometimes not!!
How come #2 my 2005 ungaraged Class C motorhome goes 5 years with fantastic thread left on it's tires (and I keep them clean) and the tires' sidewalls are full of cracks/checks? (Tires almost entirely in the shade, Aerospace 303 used on the sidewalls of it's tires, and usually driven on several RV trips per year but sitting months in between!!
Pickup = Cooper tires.
Motorhome = Michelin tires.
The motorhome is about to get it's 3rd set of Michelins since we bought it new in 2006. Outstanding tread life but terrible sidewall life.
:h :h :h :h :h :h