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Originally Posted by hawkeye680
Austin that was a very good set of instructions. One question I have that probably is a stupid one, maybe I just haven't thought it all out. Why not lower your tire pressures in mud like in sand? And like I said, I know I am probably missing something PAINFULLY obvious.
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That was given as a general rule. There are types of mud and muck where you'd want to try lower pressures, but generally mud is of the type that is better done with higher pressures.
The air pressure in the tire affects how stiff the tire and sidewall are, and ultimately the contact patch, or the amount of tire rubber that is in contact with the ground. With higher tire pressures, the tire is kept more rigid, giving a more narrow contact patch. With lower tire pressures, the tire squats/sags/droops, which widens out the contact patch
It's a matter of force applied per area - as in pounds per square inch. Your truck weighs 5000 to 5500 lbs. Assume for a second (and this is *not* a correct assumption) that you have perfect weight distribution and 4 equal corner weights. You've got 1250lbs resting on each tire. On a P285/70/17 tire at 35psi, I'll guesstimate you've got about a 9" wide by 4" long contact patch, or about 36 square inches. The same tire on the same wheel at 5psi, you've got about a 12" wide by 9" long contact patch. That's the difference of your truck exerting 35 pounds per square inch on the ground and only 12psi.
In sand, the objective is to float. With higher pressures and a narrow contact patch, the tire will dig in and the truck will go straight down. Lower your tire pressures, the truck will float on top of the sand. The increase in traction more than outweighs the loss in ground clearance.
In most mud (and snow) you want higher pressures. With the more narrow contact patch, the tire will actually dig through the loose stuff on top and get down to a harder surface below.
If the mud is deep enough that you can't dig through the loose stuff on top, then you're better off trying a lower pressure. To find mud this deep, though, you usually need to look for it.
If you do lower your tire pressures to play around in the sand, though, you need to remember to raise them back up before you start driving fast again.
Tires blow out due to heat. Heat is caused (among other things) by the movement of air inside the tire (air being pushed out of the bottom part of the tire). With lower air pressures, any tire will flex more while driven, and the result is more heat generated. If you generate enough heat, the tire will blow (ala Ford Explorer with 22psi tire pressure).