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.

Agreed. 30psi would not be good. You and I know that with tandem axles, in a turn, at least 2 of them "drag" across the pavement - the tighter the turn, the worse it is. I could see tires popping. So, I also agree on the bias tires. They would be better, IMHO, in our applications, due to the stiffer sidewalls.

I've always inflated my camper tires to 46-47psi - letting the heat build them to 50psi on the road. I'll likely buy something similar to what I have but, it is always good to hear what others think...I might learn something. If I can find bias tires, I think I'd prefer them vs. radials.

The web site has some interesting info, perhaps too much for a simple man as myself.

I know you are good about watching your pressures, so I think you'll be fine. Too much sidewall flex generates heat, which kills the tire. I was following someone on the highway, a while back, who was pulling a utility trailer. One of the tires on the trailer was low (not flat) and the heat was causing the tire to smoke!

   Now I may need to see a tire psychologist after researching our tires I may start having nightmares. We have  Power Towing  Trail Express tires. ST 225/75/R15 8PR load range D They have a very dangerous history of tire failure. They are new with less than 200 miles on them they were the tires that came with our new axle when it was relpaced under warranty. With a single axle trailer having tire failure is something I don't want to experience. Any recommendations do you think they are safe?

   Bob I agree inpart what you are saying regarding important safety information that all should be aware of things relateing to safety. I think Doug has done a great job and will continue doing so. And in time if a safety topic of some kind should be created it will happen. Sorry if I am not understanding your post but I hope my reply is of some help. As the safety of our tires I'm hoping the manufactuer has corrected the problems. 

Originally posted by David and Danette    Now I may need to see a tire psychologist after researching our tires I may start having nightmares. We have  Power Towing  Trail Express tires. ST 225/75/R15 8PR load range D They have a very dangerous history of tire failure. They are new with less than 200 miles on them they were the tires that came with our new axle when it was relpaced under warranty. With a single axle trailer having tire failure is something I don't want to experience. Any recommendations do you think they are safe?

You have the SAME tires that I do, except mine are Load Range C. I am into my 6th year of use on them and they have performed well - no issues. I would buy them again, if that means anything. Keep in mind that mine are well within their rating (60%, or less, of maximum load).

Personally, I think keeping an eye on the pressures (not letting them get low) is critical to good safe performance. Also keep in mind, I'm not a tire expert - quite the opposite. How much does your loaded rig weigh? Divided by 2 would reveal the load per tire, assuming the rig is roughly equal side to side.

I just followed a link in the above web site and it reveals some interesting info on trailer tires, per Discount Tire

Trailer tire info/Discount Tire