Deflating Tires for Unimproved Roads

[Willywalderbeast]

Hi Wally - that's amazing that you could take your Chinook out on the sand like that. Out here in California there's a state park in Pismo Beach where you can drive and camp on the beach. I camped there once years ago and managed to get my van conversion stuck. Now that I can easily air-down and up I'll give it a try again. I guess having six wheels on the ground helps with traction more than I thought.

Ive been to Pismo Beach a couple yeas ago on a motorcycle trip. Im surprised you got stuck, sand was very hard packed when i was there. Yes the rear dual wheels aired down have a very large foot print!

[pdemarest]

I was there in a Ford Van conversion - no dual wheels. The good thing about Pismo is there is always a bunch of guys driving around in their monster trucks and they love to pull people out of the sand. My experience getting stuck there had more to do with stupidity than traction. Parked too close to the water and later that night heard the sound of water close to my van. Got up in time to see the tide coming in and my front wheels were already buried. Guy near my spot with a 4 x 4 truck threw a strap on my trailer hitch and pulled me out. I have to say that regardless of what vehicle I'm driving the real problem with most off road adventures is ground clearance. Not a problem at the beach but then traction becomes an issue.

[Scott]

Parked too close to the water and later that night heard the sound of water close to my van. Got up in time to see the tide coming in and my front wheels were already buried.

I had this happen at Pismo too, Paul. I looked at the tide charts and figured that I had plenty of distance between my rig and what would ultimately be the high tide line, which was scheduled for something like 1am. I had the rear end facing the sea, and the surf just barely kissed the tires while I was sleeping. Well it was enough to make the rear end sink about 6 inches . It was raining in the morning, but a few minutes with a shovel and a generous, judicious application of throttle got me out. Too lazy to air down, but got out fairly easily and I was fine on the sand otherwise at 55psi. I also was stuck in the sand briefly on High Island, TX, but it wans't a big deal. I've been on many other beaches and did just fine. I currently have an open differential, but I think dually with all terrain tires and an air locker is the way to go versus 4x4; ARB locker is on the list. And as you say, clearance is usually the limiting factor. Usually.

[pdemarest]

Hey Scott - I know you've noted this someplace on here before but what pressure do you run your tires at normally? I aired my rears down to 50 psi and the front tires at 55 psi and the ride is really improved, especially in the rear, but I want to make sure I'm not running them too soft.

[Blue~Go]

I'm not Scott, but what are your weights for front and rear axle when loaded for travel? And what size tires are you running?

If you were running the stock tire size of LT225/75R16 E, then your pressures would be as follows:

55psi front would correspond to a front axle weight of 4,120#
50psi rear would correspond to a rear axle weight of 7,060#

Here is the chart (click to enlarge), which will allow to to select pressures based on weight. If you are running a different tire size then there should be a chart for that somewhere. You of course don't have to run these exact pressures, but they are what is recommended.

[Scott]

Hey Scott - I know you've noted this someplace on here before but what pressure do you run your tires at normally?

I'm diligent about checking pressure (and temp [nerd alert]), but a bit of a slacker when it comes to making precision adjustments. Unless we're below 50, I don't care. YMMV.

[pdemarest]

Hey Blue - I don't know what my front and rear axle weights are - never had it on a truck scale. I am running the stock tire size. I've had to run around town with my rig since I went to 55 in the front and 50 in the rears and I haven't noticed much difference in terms of handling/sway. I know I won't get as many miles out of the tires by running them at lower psi but I figure the tires will need to be replaced long before the tread is gone.

[Blue~Go]

What makes you say you won't get as many miles running them at "lower" psi? I mean, presuming that by "lower" you mean the recommended pressure that is lower than the 80psi max?

I guess I figured the recommended pressure was a combination of what would make them run cool and also expose the most tread to the road -- and then wouldn't that tend to give the best tread life as well? Like you say, they will usually age out first anyway, but I never knew or thought that running at recommended pressure by the weight chart would diminish tire life.

[pdemarest]

Hi Blue - I'm assuming that if I run the tires at a lower psi than the usual 65 front/60 rear that the tires will wear the tread down sooner. One Chinook that I test drove had his tires at 80 psi and it felt like I was running on cement tires!

[Blue~Go]

Hi Blue - I'm assuming that if I run the tires at a lower psi than the usual 65 front/60 rear that the tires will wear the tread down sooner. One Chinook that I test drove had his tires at 80 psi and it felt like I was running on cement tires!

I'm not sure I see that though. Because why is 65/60 "usual"? I mean, unless you weigh really (really) high or have completely different tires. But what I'm saying is that I would assume that inflating according to the chart for one's tire size and one's scale weight, you'd get the best situation for tire wear/heat/traction under typical driving scenarios.

So lower psi than recommended for weight would have the tires run hotter and tend to wear down the edges (I'd think); and higher than recommended would have them run bouncier and wear down the middle (plus perhaps less traction if you want a certain amount of tire on the road).

If 65/60 is the recommended pressure for your weight and tire size, then I'd agree. But for the stock tire size you'd have to weigh 4,500# front axle and about 8,000# rear axle. That'd be considerably over the weigh rating for both axles and the GVWR as well (and I'm presuming you're not at those weights?). If you have different size tires, then there is probably a different chart. But I'd still think that running in the vicinity of the chart's recommendation for your tire size and actual weight would be best for the tires is what I'm saying.

If you know differently I'm all ears and would like to read any documents. Because I don't want to be giving bad advice, or inflating my tires wrongly.