How Low is Too Low on LT Tire Pressures

[ACEd]

Ram 3500 SRW LT275/70R18 Load Range E,
Tire specs on my 2015 were 65 psi front 80 psi rear and computer did not like me to drop rear pressures too low. I read various threads suggesting as low as 35 psi in rear on empty truck.
My question is this - How Low is TOO Low on these LT tires. I remember old passenger tires ran 5 psi higher than door sticker at high speed (back then 70 mph was considered high). Rationale was they flex less and therefore have less heat buildup. And I have always felt that was good advice - so in car I typically run higher than sticker pressures at 80-85 mph. (Yes I know radial passenger tires are not same as old bias tires which had thicker sidewalls and more flexing in the tread area that built up more heat.)
So I am very uncomfortable with the thought of running 35 psi at speed in a big heavy LT tire that looks flexed and underinflated in an empty truck standing still.
Are there any tire guys out there that can tell me if 50-60 psi is acceptable unloaded at highway speeds?
Otherwise, I think I will just go with Front tire placard pressure all around.
Thanks, Ed

 

[H3LZSN1P3R]

For an LT 10 ply tire you should not run them any lower than 40 psi for on road use… any lower they can cause separation issues inside the carcus of the tire from to much flex where the sidewalls and tread meet, it usually starts by cracking inside where the bulge of the tire would be

 

[Grateful Dad]

Ram 3500 SRW LT275/70R18 Load Range E,
Tire specs on my 2015 were 65 psi front 80 psi rear and computer did not like me to drop rear pressures too low. I read various threads suggesting as low as 35 psi in rear on empty truck.
My question is this - How Low is TOO Low on these LT tires. I remember old passenger tires ran 5 psi higher than door sticker at high speed (back then 70 mph was considered high). Rationale was they flex less and therefore have less heat buildup. And I have always felt that was good advice - so in car I typically run higher than sticker pressures at 80-85 mph. (Yes I know radial passenger tires are not same as old bias tires which had thicker sidewalls and more flexing in the tread area that built up more heat.)
So I am very uncomfortable with the thought of running 35 psi at speed in a big heavy LT tire that looks flexed and underinflated in an empty truck standing still.
Are there any tire guys out there that can tell me if 50-60 psi is acceptable unloaded at highway speeds?
Otherwise, I think I will just go with Front tire placard pressure all around.
Thanks, Ed

This might help

 

[Grateful Dad]

Not my best job highlighting, but check out a load inflation table, that one is from Toyo’s site. If you know your actual axle weights, this should let you know what psi is needed for a given weight.

2680 lbs @ 50 psi (5,360 per axle)
3,020 @ 60 psi (6,040 per axle)

 

[roegs]

As Grateful Dad mentioned, load inflation tables from the manufacturer are your friend. I've gone to the local CAT scale and know my weight when running around town empty and also know my weight when loaded with our 5th wheel. Ride quality is important to me. There is no need to run around town with air pressures that rattle your fillings out. You'll hear opinions about what somebody's cousin's friend told them, but any opinion that does not take the load tables into consideration is just that - an opinion.

 

[Crusty old shellback]

Accoding to the load tables for MY tires, I can go as low as 25 PSI.

But I don't.

I was running 40/35 F/R in the tires and it rode great. I did a 100 mile highway trip at 75 o 80 MPH with no issues. But I felt they were a little low. So after 3500 miles on them , I rotated them due to a bad alignment from the factory, had a new alignment done at a good indy shop to the Thuren specs,, and went with 45/40 F/R.

So far they are doing great and still ride comfortably. Haven't been on any long road trips yet.