Tire aspect ratio

Actually check tire info sticker in the drivers door jamb. That will give you the correct size and specs that Ram recommends for that specific vehicle. It's possible that a previous owner put on a different size and spec tire, just to save money.
I
Ken

Thanks for that info, I had no idea about it. So it's the 70's or nothing. I really wish I could have removed the Goodrich KO2's from my old truck.

When mounting a P tire on a truck or trailer that has a 3640 lb rating its required to be derated by dividing 3640 by 1.1 = 3300 lb capacity.
Another hit on the big P tire vs LT tire is fabric in the P tire isn't as heavy (mil thickness) as the LT tire.
The P275/65-18 weighs 40 lbs and a 51 psi rating
The LT275/70-18 DT weighs 59 lbs and a 80 psi rating..... and is a good indicator of the LT being the heavier built for heavy loads on a one ton srw truck.

Tireman9 rvtiresafety blog has a article on this very problem of confusing a P with a LT in the same brand/tire line.
clicky link

LTX A/T 2 Tire
Light Truck, SUV/Crossover All Terrain
P275/65R18
Load Capacity 3640 Pounds
And below it says load range E
But that is for the 275/65

And Michelin makes a
Size: LT275/70R18 125/122S E
Style: Blackwall
Load Range: E
Serv. Desc: 125/122S
UTQG: None

So I don't know why it's not shown. I'll call tomorrow

comments embedded in red

agesilaus wrote:
I got a new to us 2018 Ram 6.7L 2500 and it is mostly great. But it came with Sailun mostly worn out tires 275/R70 18 tires. Escapees right now have a fantastic discount on Michelin 275/R70 18 tires at $105 off each tire.

My understanding is that R75 means 70% or the height of the tire and R65 means 65%.

I assume that not a problem. The ones I'm looking at are

Assumptions can get expensive

Michelin P275/65R18 114T LTX AT2 DT

the "P" indicates a 'passenger car' tire and has to be de-rated min of 9% when used on a pickup/SUV

Some countries will fine the tire dealer and tow a vehicle away if it has the wrong class of tires on it

Your TV should have LT class tires of the size your manual says and if you change the sizing...you are re-engineering your suspension

Many will say just do it or go for it, but they have no skin in your game. If it doesn't fit...expensive to replace/buy a new set...if it under rated...potentially dangerous situation at the limits

LTX AT2 at $245 discounted

the "LT" indicates a 'light truck' tire and does NOT need to be de-rated when used on a pickup/SUV

These are images representing how aspect ratio affects the tire/wheel combo. Lower aspect ratio of the exact same section width & wheel dia will change the overall tire dia & width

It is the ratio of section width to sidewall height. A wider tire with the same aspect ratio will also be slightly taller. The same width tire with a higher aspect ratio will be taller, lower aspect ratio will be shorter.
You don't want P tires on that truck. I'd put load range D or E on it.

You want LT tires not P tires.
And I think you may have posted the wrong size you were thinking of because you are asking about the difference in height of the same size tire.