Jeeperz Creeperz

Ok so my 35/12.50/R17 Nitto Mud Grapplers arrived today and in about an hour ill be putting them on. Seems as if everyon has there own opinion on PSI. This is my DD as well as my daily offroad toy (i almost always air down off road). As i wouldnt mind keeping a smooth ride what psi should i run?

I have aftermarket front and rear bumpers winches and all 8 flex arms, i weigh in at about 4600 with me and the ol' lady. These tires are psi rated for a 8000lb truck so im lost..

I also got cracked for asking this question because i assured her when making the purchase they would handle better then my A/T's...

afpilot82

It's going to depend on how your rig is set up, how much it weighs, etc. but I would advise 30 psi as a good starting point. You can then do a chalk test from there. I think you will find most guys running in the mid-20s to mid-30s range.

Jeeperz Creeperz

As i stated "4600"..

On the other hand thanks for the input! i think ill run 28 at first. Seems as if others bounce anywhere from 26-32psi

blueice

Here is how I determine on road pressure.

First use the following formula to get a good starting value. I got this formula from the forum a couple years ago.

V = Gross Vehicle Weight including passengers and gear
M = Max PSI of tire
L = Max load of tire
P = Starting PSI

((V * .35) / L) * M = P

In your case with these tires this is:
((4600 * .35) / 3640) * 65 = 28.75 PSI

You then chalk test and adjust as necessary. These have stiff sidewalls so my guess is you will be more like 26 or 27.

I increase PSI when I'm carrying more gear and/or people using the same formula and then adding the difference from my chalk test. This seems to work well for me and my tires wear properly and the ride is on the softer side.

Good luck with your dialing this in.

Gary T