Air down or not?

[bruijr]

IMHO a fully inflated tire is more prone to being punctured as it is not going to flex.

I fully agree on Doc's statement. I have experienced that myself a couple of years ago. We were riding a trail in Big Bend National Park (TX) which was covered with little very sharp rocks. Since I didn't air down I punctured two tires. I ended up plugging the tire with the smallest puncture with the biggest screw I could get off my Grand Cherokee (one in the rear hatch). It worked and got us of the trail to the repair shop within the park. I have to say, it was good learning experience for me. I was just starting offroading and ofcourse had no repair plugs with me and not much experience airing down tires.

For me airing down is essential for traction and preventing puncturing the tires.

[brendon]

I air down to about 25, lower if it's really muddy. My duratracs are load rated E and have very stiff sidewalls. I barely see a difference in the sidewall height taking out 20 PSI (I run on the streets at about 45psi), but the traction and ride off-road are considerably better. I too lost some chunks on Black Bear, but there were no punctures!

[Doc in AZ]

I air down to about 25, lower if it's really muddy. My duratracs are load rated E and have very stiff sidewalls. I barely see a difference in the sidewall height taking out 20 PSI (I run on the streets at about 45psi), but the traction and ride off-road are considerably better. I too lost some chunks on Black Bear, but there were no punctures!

25 psi is what i run on the street... why would you be running 45 psi on the street? just because there is a max pressure on the sidewall doesn't mean that's the recommended pressure for all vehicles. that max pressure rating is for max load capacity. i'll bet you dollars to donuts that if you run your rig across teh scale it's only about half what the max tire rating is.

on my old work truck the tires were rated at 75 psi. when i was empty i ran about 40-45 in the rear duals and about 55 up front. fully loaded GVW 14.5K lbs, i had the front at 65 and the rears at 75.

[brendon]

The max rating on my tires is 75, so even at 45 I am no where near the max. The stock recommended pressure for the Commander is 36 on the stock tires. These tires (Duratrac) recommend a normal pressure of 40 for the Commander. On the street, I run all my tires a little over the recommended pressures as my personal preference for driveability, and because I often do have a full load in the vehicle.

[Doc in AZ]

i would keep an eye on the tread wear as a good indication of proper tire inflating. an over inflated tire will wear more quickly in the center, under inflated will wear more at the edges. you can always do the chalk test to insure you are getting a good contact pattern.

[Arrie]

The reasson to air down your tyres is not just for grip. If the tyres are at normal pressure and you hit a small sharp stone at speed, it will ripp the inside of the ply on the inside of the tyre and over time will cause the tyre to blow out when you drive at speed on the free way. Any time you get on a dirt road I would say deflate to 1.5 bar, eaven if you have road tyres on the Jeep. As sson as I get on a dirt road I deflate to 1 bar, but I have 33" BF A/T tyres on my Commander.

[El Cid]

And the measurement device for finding the "bar" on your "tyre" ... do you keep it in the boot?

[Sal-XK]

Well, after spotting a couple of XK's over obstacles one guy had a bunch of trouble making it and I was confused at to what the problem was. Then it hit me he said earlier he didn't air down what a difference it makes uh. During the first day we headed down some long rocky service roads. About an hour into it I got fed up and air downed to 25PSI and instantly my ride smoothed right out and the family was happy again and the wife just wanted to know why I didn't do it an hour ago.

[lekmedm]

1.5 barrs = 21.7 lbs/in^2
1 barr = 14.5 lbs/in^2

Arrie is our friend in South Africa, so I guess they use barr as their unit of pressure over there. Actually, I wonder why they don't use kilopascals, but it's just a factor of 10.

[Ahmed]

I air down to lower than 15 psi when driving on soft dry sand ,, I also put it on around 10 psi when going to extreme soft sand and tough areas, and even with such pressure we sometimes get stuck