Running 20 inch wheels and tires...PSI

[89Suburban]

Low to mid-30's and adjust to your liking from there.

 

[tooleyondeck]

I've never seen recommended PSI on sidewalls of tires...only maximum pressure and I don't subscribe to running at that pressure...

ahhh you're right, I blame caffeine deficiency

 

[YukonRog]

I'm running 275/55 R20 Cooper Discoverer AT's on Centerline Rims and I run them at 40psi after watching the wear pattern.
Here's an old school trick... buy some white chalk and find a clean level parking lot or non busy road. Rub a wide 4-6" line across your tires on the tread and then slowly drive 60 to 75 yards. Get out and study the wear. You can also check alignment (toe) really well with this method. An under inflated tire will have a darker strip of chalk down the center for example. Contact areas wear the chalk off!