I own  2000 G/V that is stock now I'm going to put a 2" lift in very soon. I was going to run my Toyo M-55 tires of my dually which are 245's and 10 ply. The tires have a 80lb psi rating, my question is that my stock tires are rated for 40 lbs I was wondering if the stock rims will hold up if I run about 50-60 psi with the Toyo tires. What is every else running for psi with there stock aluminum wheels?

FullDraw

The maximum inflation pressure marked on the tire is no guide to the pressure needed for your vehicle.  For stock tires, follow the instructions in the Owners Manual - 26 psi front and rear (28 when towing a trailer).  If you exceed this, you should find that they wear far more in the middle than the edges, and give a harsh ride.  They would also have a reduced footprint, so adhesion under slick road conditions would be bad.

For larger tyres it may be necessary to vary the pressure slightly either way- you will have to observe whether they wear more on the outer edges or the center.  With lighter weight wheels, there is less weight to be supported, but the tires will weigh more, so it may just balance out.

I have stock size tires on my 2001 G.V.  They say on the sidewall "35psi" max. Is this too much?   I am having problems with the vehicle wondering all over the highway on uneven pavement at highway speeds.

26psi is correct for GVs

I run 40psi with 235/70 Light Truck construction tyres.

26psi is for Passenger construction tyres. ie the stock tyres.

Thicker walled tyres need more PSI to stop them from flexing
and building up too much heat

No problems with 40psi for mine.

When I got new tires they said to run them at 36psi, a defensive driving course said 34-36psi across the board for all cars.  When I got my car service at a suzuki dealer they put them at 30psi (without me realising for a few weeks), I upped them to 36 for a trip I did and noticed it being bumpier that before so I now compromise and run them at 32psi.  It is a bit of a balancing act between a whole bunch of different factors and it depends on what you want.  I would be reluctant to run at 26psi partly because if you drop 4psi things are getting very soft but that said, I haven't tried it either.

.... a defensive driving course said 34-36psi across the board for all cars..... 

That is plain crazy.  When a manufacturer develops a new model, he inflates the tires according to the weight of the vehicle; then he tests in a variety of conditions and assesses roadholding, comfort and wear pattern, to arrive at the best "average" figure, which he prints in the manual.  It is reasonable to depart from this by one or two psi on the basis of experiment and experience of your own vehicle, the particular tires fitted, and driving conditions.

The values vary greatly between vehicles - there are lighter vehicles than a GV with 40 psi recommendation, and as said above, the GV is 26 psi.  A lot of the variation is due to the suspension design, and the ratio of sprung to unsprung weight.

I'm pretty sure the manufacturers are biased towards lower pressures as its the easiest
way to obtain gains in comfort and they don't care how long the tyres last.

Tyre fitters seem to fill the tyres to higher pressures because they like to see even
wear and good handling.

30 - 35 psi is the most common range of pressure for the 'average' tyre to
perform well and last a reasonable time, dealerships often drop the pressures
on demo cars (20psi) to impress people with the ride quality.

If your paranoid about it then stick with the manufacturers recommendations
otherwise enjoy the benefits of higher pressure. 

If your paranoid about it then stick with the manufacturers recommendations
otherwise enjoy the benefits of higher pressure. 

In my view, the benefits are outweighed by the demerits - the tires will wear too fast in the middle, and the adhesion on wet tarmac will be poor.

Tire fitters sell tires - what makes you think they want them to last?

Only an over-inflated tyre will wear in the middle, that means getting close to or
exceeding the tyre manufacturers limit.

I started out with the manufacturers specs and got sick of always wearing down
the edges of the tyres first,  though I do like to drive hard.
For motorsport we always pumped road spec tyres to around 34-36psi wet or dry.
In the wet you need the tyre to channel the water properly to avoid aqua-planing,
lower pressure can increase this effect as a bigger footprint exerts less pressure
to drive the water out.

I would trust the maker of a component over the seller of the complete package
for specific info on just that component, especially if you are looking for some sort of
performance gain when factory setups seem to be biased on the softer side of things
as with suspension. Is firming up the soft rear dampers detrimental to anything but
comfort??

Tyre sellers will want to sell you tyres when they're half worn,
not have you bitch about crappy tyres that don't perform and wear unevenly...

Having said all that its no huge deal really when dealing with a 5psi difference,
let each man be convinced for himself   

My experience with tire/tyre sellers has been that the pressure you end up with is often the pressure that just happened to end up in the tire after they seated the tires on the wheels.  A few years ago I had some 235/75R15 muds put on my '93 Tracker and I ended up with not a single tire below 45psi!  It road like a brick wagon!  Dropped them all to around 20psi and I had even tread contact and a much better ride.

No offense Moses but my friend says the same thing to me about his tire pressure and after 2 years at 50psi or so the centers of the tires on his Chevy pickup are starting to wear noticeably.  He's got a good 15-20psi extra but just won't listen to me.

- I was referring to their tyre specs, not the $5-an-hour apprentices' work habits.
- I thought we were talking GV's not Vitaras 
- I don't know much about Chevy pick-up trucks either.
50psi is alot of psi though...

Low 30's is good for the GV, can I get away with saying that much?

Ahh the internet, you can always find an argument no matter
what you're talking about 

Low 30's will result is less adhesion, never mind the tire wear.

Here's a thought - what about the kids in the car in front, when your tires lose grip in a rainstorm because your pressures are too high?

I don't know about where you live, but in some countries you could end up in jail for causing injury, and the court would accept tire pressures as evidence of culpability.

Hey, I love kids. I even have one of my own.

You are right, I will never drive above 26psi again.

I will also sell the GV and buy a Volvo.

Just to fuel debate and since I work at a road transport research organisation I thought I should do a quick search.  I found one journal article that looked at factors infulencing the braking performance of a sedan.  They tested different tyre pressures from 24-35psi and found no statisticaly significant difference in the braking due to a change in tyre pressure on both wet and dry surfaces.

Now I'm not sure how "wet" the surface was and if aquaplaneing would have been an issue and the resport was from 1992 and it was not a GV used for testing but I don't have time to do much more at the moment (most articles are to do with trucks anyway) and this is not an area I work in, but I thought you'd all be interested in my quick 10min study of the topic.  (and I'm sure someone will find a study that shows otherwise if they try hard enough)