nitto terra grappler

I put a set of 295/60R20 Nitto Terra Grapplers on my 2011 crew cab. The wheel/tire shop inflated them to 55 psi. Im thinking thats pretty high considering the OE tire pressure is like 35 psi. What should these tires be inflated to? i dont want to wear them out because of improper inflation!

I'm trying to decide which tire to go with, i would like to hear some opinions from people that have had either one. I'm looking at the General Grabber A/T 2 and the Nitto Terra Grappler or Trail Grappler! I dont do any major off roading or anything, just want something that will go good in the...