Tire-ology

In another post, the subject of tires came up. Techntrek had purchased new tires and I will be, in the future. The post brought some questions to my mind, as I consider this future purchase. My investigations, thus far, lead me to the following hypothesis:

I am not smart enough to purchase tires, unassisted. I need someone with a PhD in “tire-ology” to tell me what tires to buy!

Just kidding – there is no such thing as “tire-ology”.    However, this web site, though dated, has some interesting information:

http://www.4crawler.com/Diesel/Tires.shtml

As I look at my existing tires I see – Load Range C, 6PR, and (further around the tire) 5 ply tread, 2 ply sidewall. I thought I have 6 ply tires but , I don’t. I have the equivalent of 6 ply tires! Quoted from the above web site:

“The Load Range rating is gradually replacing the older Ply Rating (as in 2PR) system. Ply rating at one time indicated the actual number of bias (fabric) plies making up the tire, but with the new radial tires, you often only have 2 or perhaps 3 plies making up the tire carcass with some additional circumferential plies under the tread. So a tire labeled "8PR" or "6PR" will likely not have 8 or 6 plies in the tire, but the "8PR" tire will be stronger than the "6PR" tire.”

So, my 5 + 2 ply = 6 (PR)! But, not really. This is because we really don’t use the ply rating system anymore. In my particular case, 5 + 2 = “Load Range C”. Load Range C roughly means that the tire is rated to carry approximately 1750lbs, per tire, at a maximum inflation of 50psi.
   
These are the maximums but, my camper (having 4 tires) is carrying roughly less than 1000lbs per tire, when fully loaded. Reading down the web site, regarding inflation pressures, would indicate, to me, that putting 50 psi of air in the tires is actually over-inflating the tires. There is a somewhat linear correlation between load and inflation pressure (as stated).   Since I have about 60% of the rated load on the tires, I should inflate the tires to roughly 60% of the maximum (about 30psi) and then test for proper tread contact with the pavement – adjusting as needed.

This just seems a bit low, pressure wise, to me. And, at this point in the thought exercise, is about where the hard drive between my ears overloads and crashes. The only way that I can get it to reboot is to go into the other room, eat some cookies and, watch “Gilligan’s Island”.

So, your thoughts/comments are welcome.