i'm about as much of a sand veteran as you can get in these parts, a flat beach although mucho mucho fun, seems like "a walk on the beach" so to speak.
lets see if i can put together a little "crash course/reference manual" for sand.
air pressure is directly proportionate to the size of tire you're running and the width of wheel.
for examble street tires or stock sized tires are much more susceptable to low air pressure than a 35x12.50
15psi in a car tire can look the same as 8 or 10 psi depending on sidewall rating and plys.
in regards to wheel width the wider the wheel the less effective your low air pressure experience is going to be, however minute.
with a wheel close to/the same width as your tire your sidewalls will be straight up and down.
when you lower the air pressure your sidewalls will be flexing i guess you could call it a fulcrum point, in the middle of the sidewall. (i also think with a wider wheel it is easier to roll off the bead)
if you have a narrower wheel you are putting your flex points more AT the rim and the corner of the tread.
which from my experience makes running 10psi with an 8 inch wheel more effective than running the 10psi with a 10 inch wheel.
also look at sidewall rating.
IMHO the best all around offroading tire is a load range C tire.
load range D and load range E tires are generally found with 16 inch wheels for carrying heavier loads and are equipped on trucks. stiffer sidewalls etc...
part of the reason i was a little confused the rubicons decided to go with a 16 inch wheel and the goodyear load range D MT/R, my cousin actually bought a 6th tire and ran them on his 1ton dually when he bought new wheels and tires for his.
when running low air pressure and cruising around the beach, if you're at all concerned, just get out and put your hand on the sidewall of your tire. it should be cool to the touch.
if you're watching your speedometer while cruising around on the beach and are paying attention to how cool your tires are, you are safe to go that same speed on the roads, in cold weather (teens and 20's) i've driven 50 to 60 on 10psi in my jeep but i would not try it in the summer.
what kills a tire is not driving on it with low air pressure, it is the heat and "work hardening" that coincides with it from low pressure and high speed situations.
larger tires are also more immune to speed and low pressure because the less RPM that tire is rotating, a stock tire at 50mph is turning quite a bit faster than a 35.
i ran 31x10.50's on an 8 inch wheel for a long time on my jeep and from one end of the oregon dunes to the other.
my cousin ran about 15psi and i usually ran about 8 or 10.
both did really well.
the good thing about running at 15psi is that if you happen to get stuck you know you've got a cushion.
you can go down to 5psi and will more than likely climb right out of the hole you're in.
for example my brother has an '05 long bed crew cab duramax with 35's and a 28' toy hauler.
he learned about the super low air pressure thing from another guy and was able to back out of a hole he was stuck in pushing the trailer uphill just by going down to about 11psi.
since then he has messed with others while they struggle to get up the access road into the dunes, while we are heading out to leave, he has stopped on the access road, put it in reverse and backed back up to the top with his trailer.
in sand, tire spin and deep/aggressive tread, is your mortal enemy.
bald tires actually work better than one would think.
i bought my jeep for 300$ the day before we went on our february sand run.
stock height and bald front tires and i did just fine. and i'm not talking about flat beach cruising.
if you've seen any of the pictures i've posted of the dunes on here you'll see the places things things can go in the sand.
just be smart about it and know where and what you can do and visaversa
oh yeah....
and we want pics...