new tyres today concern about preasure

Going by that theory I should be running my 10 ply Cooper ATRs at 70PSI!

Like I said>
This is what has worked for me with my tyres, 6Ply LT Cooper AT's

Personally I would probably of tryed running the 10Ply tyres at 60 or something but I don’t know, as I have never had a set 10 Ply tyres before, but you obviously didn’t by 10Ply tyres for a smooth crisp ride?

Same here, my 10 plies, max 80 psi, should run them at 70 psi by that suggestion.

I find they start wearing in the middle at any more than 40 psi, so stick to about 38psi for normal use on bitumen, empty that is.

Nope , not necessarily a soft ride, but hey it's a 4wd.

So in what circumstances would you run them at 70PSI?? Why rate the tyre at that pressure if it can’t be used at that pressure.

If they can go to 80PSI at 40PSI they are only 50% inflated which makes it sound as if they are under inflated, But as you say they are over inflated at 40PSI as they are wearing in the middle!!??

Or am I looking at this all wrong?

Like D-Jack I have the 10 ply Cooper ATR on my Prado.

I run 40 psi all round on bitumen, 28-30 psi on good gravel, 25 psi on crappy gravel or gibbers, 18 to 20 psi on sand.

Works good for me.

Anthing over 45 psi is just too rough a ride (even in a 120 Prado which ride great) and would risk wearing out the centre of my tread.

Muddy

The 10 plys (well, we all know that they are actually 4 plt, 2 nylon, 2 steel) but they are 116 load rating, so at 80 psi, they are rated to carry 1050kg each, or 2100kg per axle. Now the pajero weighs 1870kg, and 2580kg gross fully loaded. Rough guess is that the rear axle with car empty is about 850kg, and about 1400 kg loaded. So empty I am under 50% of capacity of the tyres, so 36 to 40 psi is about right, and when fully loaded I run about 50/55 psi, which is about the right ratio (50/80) of 2580 kg.
Now 6 ply tyres are about 102 load rating from memory (650kg each) , and max pressure of 50 psi? So running 32/36 empty and 40/45 full, which is roughly the right ratio.
So to run 80 psi, I would need to really overload the car! So are they a waste of time? Some would say so.

But the advantage of 10 ply tyres is less stakes through the treads and side walls from the thicker and heavier construction (mainly rubber in the side walls). Yes, it is a lot stiffer ride, but I will put up with it.
Notice on this forum that some people are running 18 ply cross plies for serious cross country work, for the staking reason. I don't need that and prefer the radial construction for road use.
It is all a compromise is'nt it :-)))

All except me that is hehe......

fwiw, I used close to what exploder said, on my 80 series with that size tyre. We got 93,000 outta the set - only one flat by virtue of a 3" nail.