Bruce,

The "P" Rating is the ID for Passenger Car use.
They are not recommended for use on our Burbs and Hoes.
There's a considerable difference in the way the P's are constructed, as compared to the "LT's", which are the right ones for our "Trucks".

For instance, you can have a...
P265/70R/16 (not right/heavy enough for our Vehicles), and a
LT265/70R/16 (the right type for us)
Both will fit, look pretty much the same, but the "P" types are wrong.

The statement "Standard Load" doesn't mean much to me. Given how varied our rides are set up, there is a vast difference in their capacities.

I may have misunderstood what you wrote...
Do you mean that the 4 and 5 ply have the same Load Rating ?

I'm not sure just how close to the 90% capacity that 2535 Lbs is for your ride. However, when replacing what you have with new stuff, you do need to consider this issue. Several Manufacturers have an 8 ply, that is closely rated. But, one needs to dig into that to find it. A well made 8 ply, will probably cost more than a standard 10 ply Tire. That's what you gotta do, to get the Load Rating as close as you can, and the softer ride as well

HA, I'm going to go out on a limb here, and say...
I bet your Spare is a 4ply. And what happened is that they pulled the (fresh tread) Spare and put it on, bought three other Tires to ride on, and sold the vehicle. Putting the best of the old 4 plys as the spare.

 

SW,
Oh, you mean that "P", Yes these tires are P266/70R17
The "Standard Load" is embossed on the sidewall, I've no idea what it means.
No misunderstanding, they all have the same Load Rating. Weird
The spare is also a 4 ply, it has a newer manufacture date of 0311, the others are dated 2610,2710. The spare has some miles on it, but the other tires were new when I bought it from the dealer.
Who says an old dog can't learn new stuff? <label for="rb_iconid_10"></label>
Thanks for the education.

 

Bruce,

Oh well, what's done is done. Just remember to go with the "LT" type next time you buy new Tires. In the mean time, keep the pressure up in them. As stated, running just under MCIP doesn't harm them any, and is the only way to utilize the Load Rating they do have.

Glad to share with you.

S.W.