I keep my tires on my Silverado at 35 PSI, when towing I put it up to 40, which is the maximum.
When I had a diesel pickup, I had the load range E which I could put in 75 PSI, but after 60 PSI it is recommended that your valve stems be brass and not rubber.

I used to put closer to the max recommended and now I have slow leaks in a couple of them. Coincidence? I'm guessing it's not good for the seal.

You are not an engineer, go with manufacturer spec on pressure.

I have a Wrangler but with 17" tires, D rated and run at 33 psi, ride is fine and wear is even. There's no reason to run more pressure, as others said the tires heat up fast and pressure will increase.

Higher pressure will give you an increase in gas mileage. This is because you are lowering the amount of tire in contact with the road, decreasing friction. This will give you less traction, not more.

My Jeep is fairly light, 28 psi all around gives me even wear across the tread. If I'm towing I add a few psi to the back. I go down to 10 psi off road.

set it to 33 or 34 and do not set it much higher than that. Set it at 51 if you want to screw up your handling and cause the tires to wear out quickly.

As a former Michelin employee, I'll simply say this. Unless you're running different size tires than OEM, you should always inflate to the values in the vehicle manual or on the drivers side door jam. That number is based on the vehicle weight and load distribution, which is why you'll often see different Front/Rear values listed.

Anyone that says over-inflating can't reduce overall traction doesn't know jack shit about how tires are designed and work.

I will say this though, under-inflation also comes along with its own issues. Anyone remember the Ford Explorer/Firestone thing from years ago? Ford lowered the inflation pressures to get the ride quality and handling they wanted, which in turn increased the operating temperature of the tires, causing them to fail. Of course Firestone also tried to blame the mess on tires made while the company was in the middle of a strike.

It's a 6 of 1 kind of thing, but I don't ever recommend deviating from the vehicle OEM pressure specs by more a a few PSI if running OEM size tires and checking pressures often.

My 96 Dodge 2500 HD 4x4 calls for 65F 70R.

Remarkable, but that's what it wants.

There is a balance. The OEM's recommendation is the best balance of comfort, mpg, and handling. I usually inflate 1-2psi over their recommendation to account for temperature changes so that I don't have to check them as often. You may get slightly better mpg. Over inflating to max will make the ride harsh, reduce tire patch, and only wear the center of the tire. I would not recommend it.

quote:

Originally posted by Snapping Twig:
My 96 Dodge 2500 HD 4x4 calls for 65F 70R.

Remarkable, but that's what it wants.

I had the same model but it was a 1998 extended cab. I kept the tires at 55, raised them when I towed. Otherwise, every bump in the road made the rear jump.

quote:

you should always inflate to the values in the vehicle manual or on the drivers side door jam. That number is based on the vehicle weight and load distribution, which is why you'll often see different Front/Rear values listed.

1000%

The chalk is good for the track when you're working with track tires (RDOT or true racing rubber) when trying to get the wear to the correct spot on the sidewall.

I run 36#'s on my Wrangler Unlimited

quote:

Originally posted by SIG4EVA:
There is a balance. The OEM's recommendation is the best balance of comfort, mpg, and handling.

This much is true. The manufacturer wants you to have the best ride, so they may reduce the PSI to give you a good ride. Makes the car "feel" good. Makes their brand look good. This is not necessarily the best pressure for those tires. The chalk test will tell you what is the best pressure for the tires you are running.
 

Funny you should mention this. When I test-drove my old '92 Wrangler, I found the owner had pumped up the tires to max-rated. Horrible test-drive! (though I ended up buying it anyway.) The vehicle bounced all over the road, and the steering was absolutely ballistic. It was not even safe, and almost undriveable. Bleeding the surplus pressure solved the problem, of course.

Follow the recommended pressures for the vehicle, not the tire specs.

quote:

Going from 33 psi to 35 psi is one thing, but I am wondering if it is advisable to go all the way to 51 psi. Anyone have any opinions?

There is room to play with the recommended pressures, found on a label on the door jamb. But I see absolutely no reason to go that high. Do you want the thing to ride like a buckboard wagon full of bricks? Also, this is not a vehicle that is going to carry heavy loads or tow, for which inflating the rear tires higher would make sense; in fact, it would be hard to imagine a worse one.

I would say stick to the door jamb spec for anything but a full sized truck. I drive a 2500HD Sierra and my door jamb is for the max load capacity. If I run the truck empty on recommended pressure my truck rides like a rock and wears out the center of the tire early. I have a compressor in the truck so I run 50psi empty and 70PSI cold. Get good wear pattern on the tires and good ride. I think heat becomes more of an issue if you start running them in the 30's.

quote:

Originally posted by rtquig:
... When I had a diesel pickup, I had the load range E which I could put in 75 PSI, but after 60 PSI it is recommended that your valve stems be brass and not rubber.

I've had a 25000HD diesel for nearly 12 years and when I tow the boat (7K lbs with trailer) I like the rear tires all the way up to 80. It just feels better that way. Never once did I consider the valve stems on those tires. Maybe I should have? interesting.

Now when I'm unloaded I like them between 45-50. More than 50 it starts to ride a little harsh. Less than 45 and it gets too soft.

I recently got a Silverado that had 20" wheels, and didn't prefer the look. Swapped out with a buddy who had 17's, and then added more size to get to a 33" height.

He and I spoke a few days after we'd swapped, and he mentioned that he'd adjusted down the pressure from 45 lbs where I'd had it (i.e., where the guys at Discount Tire had put it), and brought it to 35lbs for a better ride quality. Somehow I'd missed that they inflated to that high, and after the fact I DID recall that the truck's suspension had been a bit less gentle for the last few hundred miles....

I usually keep mine 32-36, maybe 38 if I'm feeling hateful toward the tires.

Does anyone factor in what the tires look like to the PSI equation? On my Grand Cherokee, with the tires inflated to the door jamb pressure, the tires look to be underinflated. Meaning in the lower portion of the tire, the sidewall is rounded out, and not "straight" as I believe it should be. I would have to bring the pressure up significantly to get them to look "right".

quote:

Originally posted by jayhalsey:
Does anyone factor in what the tires look like to the PSI equation? On my Grand Cherokee, with the tires inflated to the door jamb pressure, the tires look to be underinflated. Meaning in the lower portion of the tire, the sidewall is rounded out, and not "straight" as I believe it should be. I would have to bring the pressure up significantly to get them to look "right".

That is what radials look like by design, now bias ply tires, that's a different story... Eyeballing a tire and thinking it is over/under-inflated is a true folly, unless of course it's flat.