I have a 3/4 in. lift with rancho rs 5000 shocks on my grand with 30x9.50-15 tires. The door says to run 36 psi all around, but it rides real bumpy. What tire pressure would be best with this setup? thanks  

What psi does your tires have printed on them???  

50 psi max  

Try around 45 psi. cold          stiff side walls sometimes leads to a rough ride. good luck  

the rating on your door is for that stock setup and tire combo , when you go bigger you have to adjust as you go. on the reverse side you might need to go to a lower psi for a better foot print while going off-road. test test test  

repeatedly drive through a puddle, adjusting your tire pressures until the tread pattern left on the pavement is EXACTLY the width of your tread face, and the pattern looks clean and uniform....this will give you even tire wear and a much smoother ride.  

Nicely put