BassAckwards

At 35psi your tires will hold 7,560lbs total. So it would carry the legal limit of your truck and have 600lbs to spare. So you would be okay to run at 35 and if you knew you were maxing out the truck you could bump them up if you felt more comfortable.

But 35psi on an empty truck would be fine!

stmar

35 is what the door jam has. My confusion was that the stock tire, 255's on the jam, were changed to 265's. So from your calculations the tire pressure would not change and could be 35 for 255's or 265's?

BassAckwards

You need to check a tire load index chart for proper inflation anytime you change tire sizes or load range and load ratings.

It just so happens that the new tire you put on will hold more weight than you even need at 35 in any situation. Dealers might put you at higher pressures to cover themselves for several reasons.

1. Nobody checks their air pressure regularly enough to run at just above GVWR. Gotta check it monthly, don't wait for the TPMS light to come on and tell you.

2. If they leave you only a 600lbs cushion for hauling max payload and you don't check your air before doing it, you could have a blow out because of low air pressure and the tire became overloaded, they could be held liable. So they set the tire to hold the same weight as your old tire to keep the same buffer.

3. They don't want to take the time to look up what you need and will guess and set it really high.

I have an excel spreadsheet load index chart that I had created for personal use and quick reference at work. I am working on a way to get it embedded here on the forum for everyone to use.

Scuba_Dave

PSI - pounds per square inch
Doesn't matter if its a 255 or 265 it will be the same psi rating
It will take more air to fill a larger tire, but same PSI
My old 255's said 44 psi Max, new 265's still say 44 psi Max
IMO you Never want to fill near Max pressure, tire heats up...exceeds Max pressure - bad things happen

Different road conditions you want less PSI (driving in sand, off road etc)
Over-inflate your tires (above recommended) & the center will wear out faster
Under inflate & the edges will wear out faster
In both cases braking will be effected too....not all the tread in contact w/road
I check mine on a reg basis, comes from having a slow leak in 2 tires before
I know lots of people probably never check theirs unless it looks low

The chalk idea is great, tells you when you have full tread contact
But for me changing from a 255 to a 265 I'll stick w/Factory recommendation
I don't have TPMS

If you tow/haul on a reg basis higher might be better, but check the tire ratings
I type too slow - BA covered that
No experience w/really large tires, but you went thru the same tire change I did

44 psi Max is your Coopers:
http://www.tires-easy.com/cgi-bin/rs...7%20115T%20OWL

stmar

"I have an excel spreadsheet load index chart that I had created for personal use and quick reference at work. I am working on a way to get it embedded here on the forum for everyone to use."

That would be useful, look forward to seeing it, thanks again.

techrep

iTrader: (1)

Softer...

stmar

"My old 255's said 44 psi Max, new 265's still say 44 psi Max
IMO you Never want to fill near Max pressure, tire heats up...exceeds Max pressure - bad things happen

44 psi Max is your Coopers:"

Dave,
My tires have a max of 50 PSI. I wonder what the difference is? Mine are AT3's, LT265R70/17.

BassAckwards

He has P-Metric tires and you have LT Metric tires.

stmar

P as in Passenger (car) vs. LT (light truck)? Makes sense, thanks for clearing that up.