question about tire pressure

The purpose to chalk test your (non stock) tires is to find the ideal pressure for max. tread contact. Over inflated will wear the middle of the tread too much and under inflated will wear the shoulder edges too much.

I have no issue with running the BFG junk tires (Rugged Trail TAs) at 29 front/ 32 rear but once I replaced them (at 20,000 miles) with Hankook Dynapro ATMs (which have a higher max psi and weight rating, still P metric not LT), I found 29/32 was too soft and first ran them at 38 psi for a while, eventually dropping to 35 psi after I performed the chalk test to see actual road contact. I now am running Cooper/Destiny Dakota ATs at 34 psi... as they are also rated higher psi and more weight then the BFGs that came with the truck.

 

I knew a dude who kept one of his spare tires at like 120 psi and used the air to air up his tires a bit after wheeling. I would never recommend such a thing but I agree that tires can generally hold a lot more air than listed.

I disagree. Off road tires have come a long way in the last 10-15 years and the 4x4 community regularly airs down with minimal problems. I would say that as long as the spread isn't too great, like constantly going from 50psi to 8 psi, it's not much of an issue.

 

While 99% of your post is spot-on, I don't completely agree with this.

Underinflation damages tires both through excessive heat and overloading.
General off road use and even rock crawling will not overload the carcass at 15-20psi.
Heat is a function of friction, and at the low speeds of off roading, the tire is able to shed the heat before it reaches damaging levels.
Note, I am referring to casual off-roading and not high-speed extended runs.

Hundreds of off-roaders air their tires up and down every weekend and are not seeing failures.

 

When I bought my truck 6 months ago they had that in it and I didn't know any different.. fuck my life the dealership is fucking retarded.

I'm gonna lower them to 50 and see if it drives any better, wonder if that's a contribution to my vibes

They are load range E LT's, says max 80 psi cold but I put them at 50 and gonna test right now

 

The bumps and dips are waaay smoother but the vibes are worse now. I noticed some weights came off my rims today when I was cleaning them, between getting them fixed up and a balancing do you guys think it will help? Lowering from 50 psi will make the vibes even worse I fear

 

Yeah, you're going to need to rebalance them if some weights came off. Up at speed you're going to have some shimmys and shakes otherwise.

 

My summer tires are that rating and I run 50 psi at the recommendation of my tire guy. Makes the ride a little rough but saves the MPGs -- I still average 20 MPG, I'm 2.7/4 cyl, but these are heavy tires.

+1 for sure!
I suspect your vibes are more from the missing weights than from the pressure in the tires.

 

I remember when radial tires first came out everyone overinflated them because they could see a slight bulge at the bottom of their front tires and they thought they were half flat. My mother even stopped once and put over 50 pounds in her front passenger car tires because they looked flat. If your front tires don't have a slight bulge or your truck seems to ride harsh or bounce over bumps you are overinflated. This is what the voices in my head tell me. Also when in doubt call and ask your tire manufacturer. Most times they will tell you to go by the door sticker or close to it. Don't forget most LT tires are made for trucks that weigh almost twice as much as a Tacoma. Just my $0.02. Drive safe.

 

This guy lol. Dude I have ran down the highway at 70 with ZERO psi before. It's a little squishy in the corners, and yeah the tires were warm, but they were fine for a few miles (trailhead to trailhead, didn't feel like airing up). I'm running military surplus tires manufactured in 1992! You know how many flats I've had in almost 50K miles? Not one. I did have a few with BFG's (9 in one year I think lol) but those were from sidewall tears and using them for something they were not designed for. Safety Third!

(was doing about 80, hit a rock took out two rims)
http://youtu.be/2SgAzs9-hLk?t=40s

 

Initially when i had checked them a couple of weeks ago one tire was at 60 psi and the others were like 45/50/55. Put them all at the highest of 60 and the vibes weren't nearly as bad. Maybe it was just a coincidence but i'm going in for my balancing in a couple minutes, hopefully it helps

 

so i had new tires installed on my truck
went from P245/75r/16 to LT 245/75r/16 E load rating General AT2's. they're rating is 84 psi, door tag indicates 29 psi. my mileage really dropped at the 29 psi filling which is what the tire installer filled them to. so i topped them to 42 psi.
should they be ok at that psi?

 

+1 Max tire loading is achievable at the max listed pressure. So if you have a big Ford Duramax with a 12' camper and 4,000 pounds of stuff in it you may need to inflate to max pressure to drive to the local mall.

If you want the best tire life adjust tire pressure as indicated by the chalk test. Best fuel mileage may well be at top pressure, but you tires won't last very long and it will ride harsh as hell with nearly no sidewall give. Off-road traction is poor and actually dangerous at 50 or 60 psi.

Somewhere in the 28-32 psi range is what works for me.

 

Best mileage will be at top inflation, as well as best tire life, and greatest resistance to hydroplaning.

I've always run at or near top inflation, and have never had a tire wear down the center. Ran my Duramax at 80psi and at 40,000 miles, tread wear on all 4 was dead even all the way across. When I picked up a screw that was too large to repair, the guy at America's didn't believe that I had 40k on the tires when he compared the tread to a new tire.
I ran 44psi on my '91 Ford Escort... thing rode like a covered wagon at 30psi, so it didn't make the ride much worse, and as long as I rotated the tires every 5k (rear suspension feathered the hell out of the left rear), I'd get 60k out of cheap 40k-warranty tires... and they wore the outer edge before the center.

But yes, offroad traction suffers badly at higher inflation levels.