Good question, rbatelle. I have never seen where inflation pressure changed the depth of the tread. I guess it may be a possibility, but as long as you have kept the inflation pressure within the recommended limits on the tire, I have measured mine at 80psi and at 45psi and it measures the same. Running the maximum pressure (80psi) may change the size and shape of the tread patch that actually hits the road from what it looks like at 45psi, thus changing the wear pattern across the tread, along with making the tire tread look more rounded from sidewall to sidewall, but I have never heard or seen it lower the tread depth just from increasing tire inflation pressure.
I think that they just lowered their tread depth from 15/32" to 14/32". Why? Your guess is as good as mine. But I have some ideas as to why... . In the past 15 years, I have seen more load range 'E' tires dry rot to the point of being unsafe yet still have lots of tread depth left, more so than tires that are worn bald to the point of showing the cord through where the tread was. Does this mean that there's too much rubber on the tread? Can the factory make the same tires with less tread depth (i. e. using less rubber overall) and still get by with the tire buying public? I don't know. Personally, I would like to see a tire that provides great traction in all conditions (not too hard of a compound), last as long as what I have had before (70K+ miles thus not too soft of a compound), and resist UV weathering and cracking so that the tire will last longer than 6-8 years. But would that help the manufacturers sell more tires? I don't think there's much of a push to do that in the marketplace. We've already got rubber down to an art and a science such that we don't have to replace fan belts, radiator hoses, and heater hoses every year like I did on my dad's late 50's-early 60's autos. And I am grateful for that!
I think that price is the major factor that is driving the research & development at this point, not just the quest for the best tire that could be made and sold. Since price is the major limiting factor in selling your product in the marketplace, and since manufacturers must sell their tires in order to stay in business, the challenge is to make a product that will be widely accepted, have a fair reputation, sell it cheaply enough to be competitive, and to attract enough customers to stay in business. I do not subscribe completely to buying the cheapest product out there when it comes to my tires, but for the average buying public, that's the number 1 issue that most tire dealers are hit with. What's the total cost out the door for my set of 4 tires?
So, overall, will that missing 1/32" of the original tread depth make a difference in my tire purchase? I don't know, but if it goes as I suspect, probably it won't make any difference at all. The only thing I feel remorse about is that 3 years ago, these tires were 1/2 the price of what they cost now. But if I had purchased them at that time, would they have been 1/2 used up from oxidation of the rubber in the 3 years of storage? Of course, 3 years ago, diesel fuel was 1/2 of what it costs now, so why am I complaining.....
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