Alright so I was in box canyon, Arizona this weekend when I blew one of my bfg radial long trail T/As in P265/70r16( I know not really an off-road tire for crawling over rocks but I was itching to get out there). so I slapped on my spare and finished the run and when I got home I noticed my other bfgs were chunking out so I decided to put on some Goodyear wrangler STs in P225/75r16s that I had in my garage that have about 45% of tread left while I saved for other tires. Well I mounted them and had them balanced and I don't know why but my ride got way harsher and I get a nasty vibration after 70mph... The tires say max psi is 44 so I put 40 in them, could that be my problem? Should I run just a little less pressure or just get used to the ride as it is?

Did you have vibrations before mounting those tires? ...and what pressure were they balanced at?
Personally, I rarely take my truck above 70mph, but if the vibrations aren't that bad at lower speeds I wouldn't worry too much as long as you don't plan on running them long... or you could go get the new tires so we can go run box canyon together I've been dying to get out there myself

they need to be at 30-32psi.

40psi is kind of a lot. I run 35 in my E-rated coopers.

Yeah I did but I thought it was my worn out tires... Yeah they are just temporary so I guess ill just live with it for now. Yeah it's getting nice and cool now so it's the perfect time to go!

get them rebalanced.

the tire pressure has nothing to do with a vibration.