Tire Pressure and Compressors

[Arturus]

As I understand, different conditions call for different tire pressures...obviously rock crawling tire pressure needs would not be suitable for driving on roads or gravel-strewn surfaces...questions:

1. How would one acucurately gauge (no pun intended) the proper tire inflation for the given situation?

2. Do you have any recommendations on decent air compressors that can be plugged in or charged using the inverter power outlet / is this even a possibility? Any that would work running off the auxillary (read: lighter) jack which would procude enough PSI for eextended periods of time without frying anything?

I'm heading out to Kern River then Death Valley Memorial Day weekend and would like to have my arse covered when out in the middle of the desert 150 miles from nowehere.

Thanks,

Art

[JimmyHoops]

It will behoove you to get bleed-off valve adaptor that will allow you to deflate your tires quickly. Otherwise you will be there all day. On the compressor front, you might also want something a little faster then one you plug into your cigarette lighter socket. If you intend on doing a lot of inflating/deflating you might want to consider one of these:

http://www.sunperformance.com/quick_air_2.htm

[Kansas Law Dog]

Arturus - I have interjected my comments below. They are opionions, not necessarily factual, so if someone else wants to comment, please do.

Arturus previously said:

As I understand, different conditions call for different tire pressures...obviously rock crawling tire pressure needs would not be suitable for driving on roads or gravel-strewn surfaces...questions:

1. How would one acucurately gauge (no pun intended) the proper tire inflation for the given situation? In mud and sand it is not uncommon to air down to 15 psi and sometimes less. Hard rock crawling it is typical to maintain a slightly higher pressure 18-20 psi. The key is to be high enough to prevent breaking the tire bead from the rim and losing all air, while maintain enough tire sidewall to keep from allowing the rim to come in contact with rocks.

2. Do you have any recommendations on decent air compressors that can be plugged in or charged using the inverter power outlet / is this even a possibility?Someone else has mentioned this somewhere, sorry I don't remember where. Any that would work running off the auxillary (read: lighter) jack which would procude enough PSI for eextended periods of time without frying anything?Yes you can use a 12V compressor to air back up, but it will take some time so you don't overheat the Black & Decker type compressor. The FJ circuitry will be okay, but the little inexpensive compressor is not made to air up four tires non-stop. As cheap as these little compressors are, you could buy two and carry the second one for redundancy.

I'm heading out to Kern River then Death Valley Memorial Day weekend and would like to have my arse covered when out in the middle of the desert 150 miles from nowehere.

Thanks,

Art

[highbeams]

, both are good answers
there is a book, "the 4 wheelers Bible" he has a very good explanation of when and where to air down, and what are the effects and reasons
a word about compressors, an electric will have a duty cycle, basicly it is the number of minutes you can safely use it a hour without burning it up, as a general rule, the longer the cycle the more it cost. Now, you need to see how long you will be using a compressor to figure out if the cycle is good for you, nothing is more of a bummer than waiting for a compressor to cool down to finish filling up
another solution is to carry a bottle of compressed air, and use it
however you need to be sure to have a VERY good way to secure the bottle while wheeling, it is heavy and can become quite a missle in the truck if something happens and it gets airborn.
Not to pimp the company, but these guys make good compressors
http://www.viaircorp.com/4x4.html

[1 Bored Clerk]

I've been looking for a good write up of a compressor test. I haven't found one yet. I'm interested to hear what folks are recommending. Viair and QuickAir so far, huh?

[highbeams]

1 Bored Clerk previously said:

I've been looking for a good write up of a compressor test. I haven't found one yet. I'm interested to hear what folks are recommending. Viair and QuickAir so far, huh?

onboardair
and
airboss
are other good products besides the 2 you mentioned

[Topless4runner]

The Full-size ARB compressor is decent. another alternative can be found HERE and the thread at TTORA can be found HERE . its decent, for the money. that particular compressor cant be found at that price anymore, but similar ones can be had for a little more dough, still worth it for what you get though.

As far as tire pressure goes, i have almost no experience rock-crawling so i cant really say about that. on sand, however, i have run as low as 10 PSI without losing a bead. 31x10.5 BFG MTs on 15x8 rims. othe than sand i havent done much with less than 15-20 PSI. general purpose wheeling, otherwise known as "two-trackin" in my neck of the woods, i rarely touch my tire pressure, but its nice to know that i have a compressor on hand so i have the freedom to air down if i need to because it sucks driving 30 miles to the nearest place with air at 10 - 20 mph for fear of losing a bead or overheating on the road at 15 psi.
Also, keep in mind that if you aren't doing anything too challenging where you actually need a big contact patch to get through an obstacle, such as climbing rocks, steep inclines and other cases where you need lots of traction, you are probably actually better off not messing with your tire pressure at all. in shallow mud (<6 inches or so) you will be better off having a smaller contact patch so you will sink down to the solid earth beneath where you can get traction. be sure you know the depth beforehand, of course.
Another thing to keep in mind is that when you reduce your tire pressure you will lose a little ground clearance as the tire deflates and compresses more. in many cases traction is more important, but there are some instances where a little more clearance can be beneficial, like if you are 1/2" short of clearing a rock and dont have more rocks to stack, or something of that nature.

[Good Times]

extremeaire
mv-50 like what topless4runner stated above. many have tried this cheaper alternative with great results.

[Arturus]

Thanks for the wealth of information everyone.

[highbeams]

I am, at this moment trying to find a article I once read, that had air down preasures fo each size of tire. In other words, which sizes can take how low of preasure without throwing a bead.
I do not know if it includes todays modern sizes, but it could be a starting point for us.
Another point, it has been mentioned about loosing clearance when you air down.
I personally feel, the increase in traction is worth it.
However, 80 percent of the wheeling you do, does not require airing down. If you fine you are in an area you want to try a few obsticles, by all means air down, however, I do not think you have to airdown for every trip.
It is good to learn to do as sooner or later you will have to just because, but it is not something you have to fear each trip will require.