Airing down?

[kohldad]

Based on my Compressor Recommendation thread, I now have a nice ViAir 450P compressor to air back up. So now it's time to start thinking about airing down.

I'm use to airing down my jeep to 15psi when I took it off-road, but have never aired down a heavily laden vehicle. I'm figuring with the TC on board, something around 30 psi may give the tire a nice float pattern for soft sand. Since I'm only at 2,500 tire, may be able to go as low as 25 psi.

Was looking for advice and experience for those more practice driving off-road.

[ticki2]

Kohldad , with all due respect your last sentence was a bit condescending .

To the topic , yes off roader's have been airing down for a long time . Because of there light weight most off road vehicles have tires that are 2 or 3 times under their load capacity so the subject becomes moot . On a heavily loaded truck with camper where the tires are almost at capacity to begin with it becomes a concern , at least for me . The charts from Firestone and Michelin are for LOW speed not for highway speed , yet they make no mention of low pressure and low speed . I am aware of all of the things you mentioned and I don't need a chart to make me feel comfortable , however I do need more than opinion. I was simply asking if anyone had found supportive data .

http://www.bridgestonetrucktires.com/us_eng/real/magazines/98v3issue4/v3i4Tech.asp

[kohldad]

You need to remember, their charts are for highway use at normal highway speeds under normal condition. Tire manufacturers do not calculate or publish charts for abnormal driving conditions such as airing down for slow driving in soft conditions.

Tires can only disappate heat so fast and tire flex generates heat. Air pressure for specific loads are calculated and tested to make sure the heat generated by the tire flex has a chance to disappate and not over heat the tire. It is the tire construction and bead surface that limits the maximum pressure which by limits max load capacity at normal speeds.

By slowing down, the tire will generate less heat for the same loading. So to generate the same amount of heat at the lower speed, you can carry more load. Some tire manufacturers provide the chart to allow this such as you found on the Michelin and Firestone. However, these charts are still for highway driving, not on soft surfaces.

Off roaders, farmers, house movers, and remote heavy haulers have been airing down tires for years for better traction and higher flotation. Since so many variables such as soil hardness, moisture content, rock size, rock sharpness, etc, it would be impossible/impratical to have a chart.

If you need a chart to reference to make your self feel comfortable about air down, then it may not be for you and suggest you stay on hard packed surfaces.

[ticki2]

kohldad wrote:
Airing down does not have any effect on load capacity when the vehicle is being driven at reduced speed on softer surfaces. Load capacity ratings for given air pressure is applicaple for on-highway driving at highway speeds.

I have search everywhere I could think of and have not found anything that supports that . Both Firestone and Michelin have charts for truck tires that show you can increase load capacity for low speed by airing up but nothing about airing down . If you have info about load capacity when airing down I sure would appreciate knowing about it .

[av8rds]

msiminoff wrote:
After seeing all these photos, I am sooooo dang jealous of you folks with "normal" wheels & tires! 😞
This is as close as I can get to the beach with my TC & 19.5" tires (notice the asphalt just in front of my truck)

On edit: Photo taken at Wright's Beach, Sonoma Coast CA
-Mark

I know one guy who does it regularly with 19.5's and know of another that does it with no adverse effects.

My tire guy said no way, but I'd sure like to upgrade to a 450/550 someday but cant lose that ability.

[kohldad]

Airing down does not have any effect on load capacity when the vehicle is being driven at reduced speed on softer surfaces. Load capacity ratings for given air pressure is applicaple for on-highway driving at highway speeds.

One must remember that at reduced pressure, there is a lot of sidewall motion which will cause sever under steer, possibility of rolling the bead of the rim, etc. This is why you only want to reduce pressure to what you need and not start off at 15 psi.

[JacintoKid]

Steve_in_29 wrote:

JacintoKid wrote:
Not to hijack the thread but, do most of you guys air down on rocky mountain trails? I've done a few passes over the years but nothing too technical and always in a stock 4x4 suv. Just curious as we may take the 4runner along with us this summer.

I always lower pressure when on rough or rocky trails to allow for a smoother ride as well as better traction. The amount I let out again depends on the terrain and what I am driving.

No need to have wildly spinning tires to make it over an obstacle when simply lowering tire pressure would get you there without the drama (and possible snapped axle or u-joint).

You will be surprised how much more capable your stock SUV can be after simply airing down the tires.

Thanks. That's what I was looking for. Just wanted to make sure I wouldn't lose any traction. Brad

[MKish]

So...would you air down for a crummy rocky washboardy road like the one to the Race Track in Death Valley? Sand sure. Nice and soft. But rocks make me nervous!

(Our camper loaded is probably around 2200lbs. on a SRW CC SB.)

[ticki2]

Does anyone have definitive information of the effects of airing down on the load capacity of tires . I have read conflicting statements .

[Steve_in_29]

msiminoff wrote:
After seeing all these photos, I am sooooo dang jealous of you folks with "normal" wheels & tires! 😞
This is as close as I can get to the beach with my TC & 19.5" tires (notice the asphalt just in front of my truck)

This is the trade off I always mention to people that want to go to 19.5" tires (or any of the .5" sizes) to stay SRW with a heavy camper.

[Steve_in_29]

JacintoKid wrote:
Not to hijack the thread but, do most of you guys air down on rocky mountain trails? I've done a few passes over the years but nothing too technical and always in a stock 4x4 suv. Just curious as we may take the 4runner along with us this summer.

I always lower pressure when on rough or rocky trails to allow for a smoother ride as well as better traction. The amount I let out again depends on the terrain and what I am driving.

No need to have wildly spinning tires to make it over an obstacle when simply lowering tire pressure would get you there without the drama (and possible snapped axle or u-joint).

You will be surprised how much more capable your stock SUV can be after simply airing down the tires.

[Steve_in_29]

One thing people should take note of from this thread is the wide variety of pressures. The appropriate pressure will vary (sometimes greatly) depending on the terrain, load and what tire is involved. For instance the stock tires on my rig needed to be aired down more then my current tires which are taller/wider and thus provide more flotation when traversing similar terrain.

Whenever traveling off the pavement one should ALWAYS bring some means of refilling tires to street pressures. The quickest way to ruin a tire is to have lowered pressure for sand and then have to drive for an extended period on pavement or high speed to reach a means of re-inflating them.

As long as a re-inflation means is present you should never be afraid to lower pressure to suit the terrain. It will prevent unnecessarily beating up the truck/camper/occupants and can make self recovery possible instead of calling for a tow (if one is even available).

The picture is the result of hitting some unexpected soft sand while still aired up. After digging out in front of the tires and dropping the pressure I was able to easily drive out of this and continue on for miles over equally soft terrain.

[Los_Nomades]

Beach camping, make your summer vacation unbelievable !!!




Sunrise on the beach.





For my dual, i run in the soft sand with 13 psi in the back and use to reach about 16 psi front.

[johnhealey1776]

Without camper I go down to 18psi on sandy neck on cape cod. I thought the other day I could get away with 30... truck did not move. Funny how much difference 12psi makes! With the buggy all together I use 35psi in the rear and 20 in the front and have for both of my beach going trucks. P.S. I mostly just chimed in for a reason to post some beach pics

[bedrocker]

Is that Jalama beach

[msiminoff]

After seeing all these photos, I am sooooo dang jealous of you folks with "normal" wheels & tires! 😞
This is as close as I can get to the beach with my TC & 19.5" tires (notice the asphalt just in front of my truck)

On edit: Photo taken at Wright's Beach, Sonoma Coast CA
-Mark