Just bought a set of 285 Michelins (replaced 265 BFG's). What tire pressure should I run unloaded (recommended with full load 65 psi cold)?

 

I have pro comps in the same size. 42 front, 38 rear. empty! a couple of suitcases or some 2x4's and up it to 42 rear.

 

If max recommended pressure is 65, I'd run 55 Front & 60 Rear. Supposedly, the higher the pressure in the tire, the lower the operating temp of the tire...Heat is the enemy.

 

Tom, did you get your numbers reversed?

I run just the opposite. There's little to no weight in the rear when compared to the front of the PSD. Hense, a bit more air pressure up front. I run 60 front, 52 rear with tires rated for 70psi cold. In 15,000 miles, my wear is very even. With front to rear rotations every 5,000 miles.

Tom is very correct, heat is the enemy. Heat that will break down the cords in the sidewall and the tread bands is caused by the cords sliding on one another. They are supposed to slide some, That's the beauty of the radial design, but it's the extremes we want to avoid. Cause of this is most often sidewall flex or driving beyond the tires design capabilties. Unloaded pressures are pretty simple to figure out. Any brown discoloration on the sidewall is usually an indicator of not enough air pressure. The sidewall is flexing and getting warm.

Beyond that, there's the chalk test. Run a thick chalk line or two across the treads side to side and drive straight in a parking lot. Adjust tire pressure so the chalk is worn off evenly edge to edge. More chalk and make some wide turns. Look at the results and adjust a little. Run this way for a week or two. With new tires, it's pretty simple to see tread edge wear. If you're ripping the tread edges, then you might not have quite enough pressure, are driving too fast and hard in the turns, or not adjusting air pressure when you do put a load on the truck.

This process works for any brand of tire. All tires list the maximum air pressure. But only a few list the minimum pressure. In many road tire designs, normal operating ranges can be as much as 25% less than maximum pressure. In most cases though, running near the maximum listed pressure is recommended for tire life. But if you see evidence of tire tread cupping, or imbalanced wear from the center of the treads out to the sides, then you're probably running too much pressure. If you're ripping the outer edges, -not enough. Too much pressure also taxes the vehicle suspension. (and the seat of your pants)

Driving style, load and tire design/rubber compound determine what pressures should be run. None of us can give you the magic number. My ten ply E rated Generals will most likely perform differently than your new Michelins at any given pressure and load. Access Michelin's web site for more tid bits of information. That's the best place to start with any tire. Go to the manufacture of the tire.

But the chalk test has worked for millions of tires. -Any brand

-Steve

 

I ran 40/45 in a 1/2 ton chevy. With a load range D, I think 50/55, 55/50, or any combination would be acceptable. No doubt when you are loaded use 65, because it is the air pressure that carries the load, not the tire. Thats why load range C can run 35 cold, D range 50, and E 65. The higher load ranges, require higher PSIs to carry the load.

The chalk test is good. Rotate often, 5K. When they get rounded on the outside edge in front, they need to be placed on back to flatten out the tread.

 

60 front / 50 rear seems perfect for me, even if towing my small trailer (3500lbs). Last time I took it for a tire rotation they aired the rears up to 80, felt like I was driving around on boulders.

 

My door sticker calls for 80 psi rear and 65 psi in the front.... what gives?

 

Those are for Load range E tires. The original question was regarding Ds I believe. I think 80 is overkill unless you are carrying a load.

 

The best way to find out what psi to run for each tire is to consult a authorized michelin dealer. They will have a chart showing the size, load rating, and load per tire, and then the best pressure for that tire. Pretty easy to get rough guess of your loads: GVW * weight distribution (front or rear) then divide that number in half to get your tire load. take this number to your dealer and ask for a inflation/load chart. Of course, you could just throw in a psi and watch your wear.

 

I still have the Scorpions--"E" range--73 all the way around since new and now with 45K miles, rotated only twice and no alignment. I did replace the factory shocks with Bilstein's and added front and rear Hellwig sway bars cause I hated the wandering of the factory setup.