On-Road Tire Pressure

[Tinkerer]

 

[TJ54]

a similar method I have heard of is to make your tire wet then drive on dry pavement, then check out the evenness of the tread pattern you leave behind,
if the pattern looks good in the middle and poor on the outside, then tires are over inflated, in the pattern is good on the outside edge of the tire and poor on the middle then you are under inflated.
I suppose you could do this in some fresh snow or mud as well.

I always found 28psi was about right on my TJ.

[Tagg]

I had the same issue and couldn't get M/T to discuss it so I weighed each axle, then stood the jeep level in the garage and estimated the foot print then worked backward to determine what the pressure should be if the entire width of the tire was on the road. I tested it by trying to slip a piece of paper under the edge of the tire and deducting the depth fron the foot print area.  I then adjusted the tire pressure to what I thought worked out to a full width footprint.  Then I painted two tire tread lugs accross the width of the tire on all 4 tires and let it dry over night. Next day I went out on pavement and wore the paint off watching how it wore.  I don't think it is an exact science but it worked out even ware at 28 psi so that is where my tire pressure is.

[JackstandJohnny]

runnin 30 in my GFs TJ with stock tires, like 30" or so.

the YJ with 35s is at 28.............

[morerpmfred]

Lots off different angles to think of , so I go by dead reckoning. (old school) When i had 31,s I went 25 psi in the front and 21psi in the back With 33,s I go 22 psi in the front and 19 in the back.  And a couple of reasons for that , driving on the highway on a summer day i would stop and check the tires with my hand for hot spots the most would be lukewarm.  By going with wear patterns on the edge of the tire you can not because the lugs go around to the side wall. With 22 psi in the front i,m still wearing out the centre to much. Al though corning wears down the lugs.  Any thing lower then the tire starts to roll when cornering. Now with 18 to 19 in the back it does wear some what evenly. And by running lower pressures like this I,m also breaking in the sidewall more so that it also flexes better when i do lower to off road pressures. Having said that if i was going to do a road trip to Ontario or Vancouver I would bump up the pressure a pound or two.

[homeguy]

Chalk works well too... just mark a thick  straight line across the tire and drive it for a while to see how it wears off.

[mike s]

Wow this is getting really high tech. So let's make it simple. Run your tires at max pressure as listed on sidewall. This will give you best fuel mileage. When your teeth fall out from the pounding, lots of us run truck tires on not truck wieght vehicles, so bring the pressure down to a comfortable level. Racing air pressure setup is fine for long hard cornering but we don't push our off road vehicles that hard, so big tires with lots of sq. Inches inside of them holding 2800 lbs up don't need 60psi. The wide tires are worse, blow up a paper bag and see what shape it becomes, add rotational forces adding to the problem...try 30 psi and tune from there. I like mine about 27psi but I try a different pressure every time I re-inflate em. Get some experience with different pressures cause the is no right pressure for every condition.

[w squared]

I think that what this debate is about is finding what will prolong the life of the tires the most without damaging the kidneys of the person driving 

[JohnB]

Weigh each axle (free scales all over).

Take the weight on the tire and divide by the maximum load on the side wall.  Scale the maximum pressure to that weight.

Example:  Scale reads 2500 lbs for axle.  Tire sidewall says 3000 lbs @80 psi

1250 / 3000 * 80 = 33 psi.

Run a little higher to account for extra weight.