Ozone is a big cause of dry rot. Tires dry rotted in an LA warehouse decades ago, led to the regulation of ozone as a pollutant.
I would never advise anyone to buy tires at Walmart. True when I had a tire problem 500 miles from home, I would have put a Walmart tire on, but then bought a new set when I got home. They may have a name brand stamped on them, but they don’t seem to be the same tires. Same for lawn mowers.
Yes. Military tires specify an ozone preventing chemical.I saw tens of thousands of military tires sold to 3d world countries when that chemical was found to be below spec at the factory.
I just had to replace a set of tires on my trailer. The one that sits facing the sun was severely deteriorated and so was the stem. The stem broke off when bending it. The tire was severely cracked all around the sidewall.
The tire that sits in the shade looked like new. Everything supple and no cracks.
UV breaks down almost everything over time…especially rubber.
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The “rules” are based on worst case conditions. They have to be otherwise it would be way too confusing for people. And they are very conservative as there is liability in making any recommendation for replacement interval. Ten years where I live and keeping them in the garage, they are still like new. Get ready to gasp. I have some close to 30 year old tires on one of my older cars that gets little use and sits in the garage. They are still quite soft and no external cracking or degradation visible. I’m going to replace them this year but I took them out on our rural street and did some serious tire roasting last summer with 600hp driving them. Cars and trucks I have that sit outside and drive frequently usually do not last more than 5 years. I had a new Camry with OEM Continental tires that looked so dangerous at 2-3 years sitting outside its whole life I replaced them with my usual Yokos and they lasted 6 years… YMMV.
When my vehicles start losing traction on takeoff, I take that as a sign and start shopping regardless…
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That proves there is more ozone on the sunny side. 
I let the old van sit for along time and the tires dry rotted faster on the sunny side then the shady side also…
Yeah, that’s why they sell those tire covers for RVs that get parked in a spot for the duration. I thought about doing that for the trailers and boats I have sitting out but never got around to it…
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I’m sure it’s both UV and ozone that damage tires.
Of course they can. However, given the situation I described, which is more likely? Ozone is subject to drifting in the atmosphere with any convective currents. So a tire three feet away should have some exposure to any local ozone as well, assuming it exists in the vicinity in any reasonable quantity. However, last I checked photons of UV frequency aren’t particularly affected by wind 
Surface ozone is caused by reactions with atmospheric pollution. The area I live is pretty clean air. I suppose we could settle this if I calibrate my quadrupole mass spec for O3 and go measure it next to the tire in question 
No need to measure the UV although I do have a UV-Vis spectrometer as well…
Modern tires also have a protectant for ozone added to the tire compound:
The problem can be prevented by adding antiozonants to the rubber before vulcanization. Ozone cracks were commonly seen in automobile tire sidewalls, but are now seen rarely thanks to the use of these additives. A common and low cost antiozonant is a wax which bleeds to the surface and forms a protective layer, but other specialist chemicals are also widely used
Spinning your front drive wheels reduces steering angle input effects? Now I know.