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Old 02-15-2010, 06:15 PM
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Tire load rating side ply clarification??

I'm getting ready to get some new tires and have been doing a lot of reading on here lately and there seems to be some confusion (prolly on my part) with load ratings and tire side ply quantities, ie; 3,6,8,10.

I keep reading where people say to make sure to get a 10 ply sidewall tire. And that tire pressures equate to that, ie; 8=65psi, 10=80psi etc.

I went to several manufacturers websites to read up on the specs of tires and had been unable to find ANY tires that listed there sidewalls at anything higher than 3 ply. I was only looking at E load rating tires.

So I did some online research and from what I could find is that the sidewall "ply rating" is used with biased tires NOT radials. The "letter load" rating is for radials and corresponds (roughly) to an equivalent of the older "ply rating"
8 ply = D load
10 ply = E load
12 ply = F load

Here's a link to one of the more informative sites. Or at least easy for me to undertand that is.
Tire Tech Information - Load Range/Ply Rating Identification

And although this site listed E load tire psi to be 80 I found plenty (most actually) of E load with max psi of 65. ?????

If anyone of the tire experts can help clear this up or has any corrections please, chime in

Last edited by uhpilot; 02-15-2010 at 06:19 PM.
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Old 02-17-2010, 07:17 PM
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The site was correct about the ply ratings. As for pressure, realize that these tires get used on a variety of different vehicles from 1/2 tons on up and one needs to realize that they need to use an appropriate pressure in their tires for their purpose. Tires normally have the "max. pres." on the tire carcass, so do not confuse that number as the press. that you should be using. I run my rears at max. press. when pulling my 38ft. dry van loaded up and the fronts at about 80% of that rating. When not towing, I drop those numbers significantly, depending on the season.

I know that's not a diffinative answer, but it should allow you to have an idea as to how to judge your tires and what you want to accomplish with them. Just remember to pick the tire design that meets your objective and keep an eye out on the tread wear and make adjustments to your pressures if there are unusual wear patterns, then make the press. adjustments. If the ride is too harsh and all other factors are normal, then let some air out to a lower press and see if that helps and doesn't affect the tires. Experience will build and you'll begin to know what tires and press. works best for your set of circumstances. I had to learn on my dually as I never owned one until this 99 PS. I went through two sets until I settled on straight treads on the front and A/T's on the back for drivers. After towing for a couple of years I was able to tune in the pressures when towing. Again, experience.

Hope this helps and I should point out, this is just one persons experience and view.
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