I was just wondering what levels people have found work well.
With my SSR's I go to 15-20 (depending on the conditions).
With my Winter Duelers I would go to 16-18 for snow.

I need to learn to type :)
I think you know I meant 'What' not 'Whay'

Originally posted by rhombus
I need to learn to type :)
I think you know I meant 'What' not 'Whay'

I fixed it. :) Good question on the poll.

I tried to hide my mistake but did not have permission :)

I was out last weekend and went down to 15 (from the 30 that I run the SSR's at). The Rover guys that I was with went down to 25 and 30 (they run there tires really high).

This just got me wondering what do other guys do.

I usually try not to go below 26 lbs unless I really need to. That way, I don't have to suffer on pavement in between trails and don't need to air back up right away. The lowest I've gone is 20 lbs, but I ran Moab at about 26 lbs (or maybe it was 24 lbs?) and it was fine. For snow I would probably start with 26 lbs and then lower as necessary. That's my general rule; start at 26 and go from there. I run on the street at about 34 lbs, BTW. Oh...Pirelli Scorpion A/T's, 31". :)

When I'm running the (only) mud/dirt trail around here, I air down to around 26. When I'm out in the dunes, I bring them down to 16-18.

On-road = between 32-38 psi depending on lots of factors

Off-road = between about 12-18 usually, depends on how much ground clearance I need and how bumpy I want the ride ... although I have gone down as far as 9 lbs. of pressure a couple times. With 11.5" tires on a 7" rim, I don't have too much chance of popping a bead.

I've never been below about 17. Was on a trail run last weekend where a guy with a CJ-7 had his rears totally empty - but they were TSL/SX tires. Damn impressive - looked like they were totally aired up (and he had that thing LOADED with junk).

Wow, my first post.

Anyway, PSI depends on condition, so a better poll would be to have several polls on PSI. I run 33x10.50r15 TSL/Radials and run 32-34 PSI on the road. When I'm in sand and mud I don't air down, I'd rather have the ground clearance, since where I 4wheel in sand and mud, deep water is usually around the corner. When I go rock crawling, I usually run between 12 - 18 PSI.

-Michael

The PSI is pretty much dependant upon the terrain and load. I run more air on rocks to keep some clearance and to give the tire some support to wrap edges and stiffen the lugs...and contact pressure.

Mud/sand just depends upon the consistancy/thrix properties, depends on any expected air time and degree of flotation needed for the expected speed ranges...from as low as the bead will keep...8 - 10 psi for me, up to 30 psi or so if there's a bottom to bite. (Ooops...There's a straight line for some one...)

Hill climb/loose surface detritus runs usually benefit from a more rock PSI type setting...say around 20 -25 psi for both on average is a good compromise.

If a newbie is trying to get a magic number...they'll just have to learn to experiment to see what works for them...some tires just work better with more or less pressure than others.

The jeep ahead of me last year looked like it was running up a climb straddling an erosion culvert with four FLAT BFG MT's. He couldn't keep the tires on the straddle lines because the rubber was slipping all over the place, and he lost his line, and flipped the jeep, almost crushing his dog (Leashed to roll bar....add to don't do list...)....So - There is a point of diminishing return with pressure.

I use an on-board compressor to make changes as needed, saves a trip to the gas station or three...cost about $40 - 50 if I remember, and can do a 32 x 11.5/15 from 10 to 32 psi in around 3 - 4 minutes, that's about 15 minutes or so to air back up as about the most time I need....and trail adjustments are much faster of course.

Good Luck!



- Lance

which air compressor do you have the only costs $40-$50 and can air up a 32x11.5 that fast. i have used one that cost that much and it take like 20 a tire. my ARB compressor take 5-6 a tire from 15 -> 33 PSI.

for rocks i air down more cause then the tire will conform more to the rocks and grip better, IMO. for rocks i am usually 15-18 PSI with my 32x11.5R15 BFG MTs. especially for crawling through creek crossing that have a lot of rocks in them.

kirk

Lower pressure on rocks also makes for a MUCH more comfortable ride...

Brent

Well I learned my lesson thsi weekend. Superjens adn I were scouting for the upcoming Canada run (PNWX). We hit some VERY new logging roads and were driving on "slivers" of what looked like slate. Result, busted tire !. I was running 28psi (yeah I am a dork).

We found some excellent trails, 6000ft with HUGE drops on each side keeping the balance took on a whole new meaning.


Claus :sun:

Did you ever buy the BC 4x4 trails book? It has lots of trails listed for that area. I think Husky Equipment (something like that, they're near Boundary and 1st) carries the book. Just call around, I wish there was a book like that for Washington.

Yep, I have been snooping for the book for a while now, but no luck. The guys from BC4x4 actually have some good runs listed on their website. BUT some of the stuff they do belongs in a Dome with a show titled monster truck.

Did you see Jens' email about the fishing?. Talked to a friend that works for Department of Fisheries, she confirmed that the fish in that river is Sockeye Salmon spawning...not under 15lbs !!!. I know what I am doing next weekend...i guess you do too eh !


C

The unit I carry on board is an old Interco Heavy Duty Truck compressor, its rated for a continuous duty cycle, and won't overheat...it is kind of noisy, but it has great flow....way more than the std ARB used compressor, I had all of my tires aired back up before some others had done one tire....that's when they ask to hook up their other undone tires typically...

For rock psi...yeah, depends upon the tire, some like it empty, some more full....but it IS more comfy low. :)

I think most people run too low on rocks as a rule of thumb...but that's just my personal observation, I watch the tires work, and they sometimes just can't grip w/o a little more air. (Of course, some people don't airdown at all....they're too high to grip properly.

Even the same rig needs different psi to compensate for the load or how wet it is, etc....let alone which tire...or how much clearance you want to sacrifice.

For example...did you ever notice how much easier it is to slice a sidewall under water, or even when in the rain, than when dry? Wet rubber slices easier, I swear! (So watch those water crossing through sharp rocks!)


- Lance

here is a great page on airing down and how much traction you get from various pressures. it focuses mostly on sand.
http://4x4now.com/sfjun96.htm

The 25% percent lower rule of thumb isn't bad...and accounts for different brand's various sidewall flex, etc.

For rocks...The only error was the assumption that the power to pull a rig over a bump would be the same power required for the rig to power over it itself. This has proved to be inaccurate in other tests, not accounting for the grip required to grab an obstacle in order to pull yourself over it...and the angle of attack factor...where by a pulled rig will be completely stopped by a verticle obstacle taller than the top of the tire's midpoint...and a self powered rig can climb up the face, etc... so - ...some tires just need more contact pressure than tread footprint to work...

As for the main thrust of the article...Sand Pressures...it was accurate, and good advice. For FLOTATION, low is the way to go.

:)

Originally posted by Lance
Wet rubber slices easier, I swear! - Lance

IMO I don't think rubber slices easier when wet.

I usually drop down to 20psi for certain events. :D:D



Oops, wrong forum :right:



You know, a person can learn alot just by hiding in the shadows. Thanks. :)

Originally posted by Goliath the X
IMO I don't think rubber slices easier when wet.

Actually, it depends on the rubber compound of the tire. Swampers for instance are VERY prone to get sliced up when wet. About a month ago I got hung up in a spot over in Dumfries (Rt 234 trails) and had my rear tires submerged. I ended up pulling out of it, but not without some sick wheel spin. I inspected my tires that night and noticed how chewed up my rear swampers were after pulling out of the hole. IIRC you've been to 234. Therefore, you must know about all the junk and shit people leave in the holes out there. Combine that with the fact that my tires were submerged in water and the end result is sliced tires.

Dog

Usually around 20-24 because alot of what I do doesn't require airing down less, but it drastically improves the ride on the rocky stuff.

BTW, regarding airing up time. I can do all 4 in less time than it takes most to do 1 tire. Gotta love the CO2. :D

Originally posted by Craigs_Tonka
BTW, regarding airing up time. I can do all 4 in less time than it takes most to do 1 tire. Gotta love the CO2. :D


Yep. I can air up a 32" tire from 12 to 35 psi in about a minute. Good stuff. The only problam is everyone else wants to use the tank too ...

:dogpile:

Originally posted by Philosopher
The only problam is everyone else wants to use the tank too ... I hear that! I usually end up refilling my tank each time because I'll air up 5 or 6 trucks plus mine afterwards. Oh, and BTW, it's spelled problem........:flipa: just yankin' your chain since you're like the walking talking spell checker :D

Simple solution.....Charge them $.50 a tire to air up...Or let them wait in line at the air pump....:devil:

It's simple math. It cost me $20 to refill my 20# tank. The tank will fill approx 40 tires according to powertank. Therefore each tire cost approx $.50 to fill.

While it's nice to have and very quick, If there's not a line at the air pump at the local gas station, I will use it if free. Most places I wheel have free air at the gas station. But if there's a line, or they are going to charge me for air, then I'll use my tank...

Although, the last time I went to use my tank I was pissed...:mad: I had removed the regulator and lost the o-ring that seals the reg to the tank valve. So It would not seal. I probably dumped $5 worth of CO2 trying to figure out where it was leaking....The moral of the story is carry spare o-rings, teflon tape and anything else that could be used to repair the tank on the trail...I now have 2 spare o-rings zip tied to the valve of the tank.

Cliff

Originally posted by wilburburns
lost the o-ring that seals the reg to the tank valve. So It would not seal. I built my system from scratch and the regulator to tank fittings have no o-rings so I won't have to worry about that problem.

I built mine from scratch also...Originally, it wasn't really an o-ring. It was more like a teflon or rubber washer. This forms the seal between the tank and reg...But I replaced it with some o-rings that I had in the garage and it works great..

You're sparked my interest though...How does your tank seal to your regulator...Does your regulator have a built it rubber gasket or something?

Cliff

Originally posted by Craigs_Tonka
Oh, and BTW, it's spelled problem........:flipa: just yankin' your chain since you're like the walking talking spell checker :D

Touche ...

Originally posted by Craigs_Tonka
I built my system from scratch and the regulator to tank fittings have no o-rings so I won't have to worry about that problem.

Mine doesn't have an O-Ring either. It has a hard, flat plastic looking washer that can't easily be removed.

Originally posted by ScottG


Mine doesn't have an O-Ring either. It has a hard, flat plastic looking washer that can't easily be removed.

That's what mine has as well.

Originally posted by ScottG
Mine doesn't have an O-Ring either. It has a hard, flat plastic looking washer that can't easily be removed. Yep, that's what mine has. In fact I didn't have one in there but when I was at the welding supply today and showed the guy, he gave me the washer. It fits snugly in the nut on the regulator so I don't think I'll have to worry about losing it and he said they don't wear out or crack like rubber.

I've had one fall out taking the tank in to get filled. I have a spare on a rubber band around the regulator just in case.

13psi on the beach, 34 on the road