Hope this is not a retarded question, but I just mounted 275/70 R18 nitto grappler with 40 psi of air and from what I feel so far from riding the truck is a very bouncy ride compare to what I had before which was 275/65 R18 bf Goodrich rugged trails. I read on the nitto's tire max psi is 80. Is the bouncy ride am expericing bececause my psi is on 40? If am wrong, what's the ideal or correct psi for city driving?

 

What's it's say is the max psi on the sidewall? My terra grapplers say 50 and I run 45....

 

I read on the nitto's tire sidewall max psi is 80.

 

Am probaly reading it wrong but it clearly says 80 psi

 

I have a 2002 ext cab and i run a 285/75-17 nitto terra grapplers. I run 34psi in the rears and 37 psi in the front. I have the E-rating also, which makes for a pretty stiff tire on a 1/2 ton truck. those pressures seem to work pretty good for me. i run this setup, only because i am not towing anything right now and it makes for a little softer ride. Just know that you should be cautious with the tire pressures, as under inflated tires can cause real problems with handling.

 

If the Nittos are a LR E with a max of 80, run them at 45-50. Anything lower can be dangerous.

 

I have that same tire on my '08 Screw and have ran 37 psi for the last 2 years. Great tire wear and OK ride, any lower and the handling gets a little "weird"

 

Thanks guys, I just inflated them to 55 psi all around.

 

I ran mine at 47.. Never had an issue

 

Might be a bit high. 50 is plenty.

 

How can that be when the tire says 80 psi max?

 

The tire handles so much weight at 80 psi. On most LR E tires, it is usually between 3200 and 3600lbs. Can't tell without knowing exactly which tire you purchased. there are at 5 different grappler tires. Which on is it, mud, terra, dune, trail, or dura.
That being said, using the numbers above, at 80 it will handle that weight. At 40 it will handle at most half that or 1600 to 1800 lbs. The GAWR of our trucks is about 3900 front and 4000 rear. So you want the tires to be able to handle at least 2000 lbs each. That is what 45-50 will give you. A higher pressures without extra weight, you will have a rougher ride and wear the center of the tread prematurely. Below those numbers, especially below about 40, is dangerous as it will cause the tires to overheat causing problems like tread separation, blowouts, etc, especially at highway speeds.

 

I purchased the Nitto's terra grapplers

 

Those have a max load of 3640lbs at 80 psi, so the 45-50 I gave you will be fine.
Just a matter of doing the math.
Some say to use the chalk method, but on the LT tires, I have seen people come up with godawful low numbers as the tires sidewalls and tread are so stiff. Some have come up with numbers in the 20s as the "perfect" pressure. Thats like playing Russian roulette.

 

Thanks for the info kingfish51, I have a good understanding now