Re: wheeling tips

[Tom Mandera <tsm1@domain.elided>]

On Wed, 2 Dec 1998, Daniel Nees wrote:

> Tom M and others,
>    When you go out in the woods wheeling, specifically muddy, mountainy,
> rocky terrain, where do you run your tire pressure? Joe C, Rob C, and I
> are going to Paragon Adventre Park on saturday and I was wondering what
> I should air down to, if at all.

Hmmm...

"Depends" 

I am by no means an expert.. nor do I have a LOT of experience (yet).. but..

I run ~30psi on the street in my 33x12.50s.  Just going down to 25psi has 
the sidewalls flexing noticeably.  20psi even more.

In the deep snow, I've been to 15psi.. my friends may run to 8psi or 
lower.. but they've been doing this longer.. and they're running a 
completely different tire/weight ratio.

IMO, rule of thumb would be to ALWAYS drop 5 or 10psi from street 
pressure.  You can start there and see how much sidewall flex you have.  
The trick is to get flex for better traction... but don't move the Scout 
over the rocks so fast that you flex right down and bend the rim (reminds 
me... I have a lot of straightening I should be doing to my steel wheels' 
rims)

In the deep snow you don't run the risk of damaging the rims (oh, be 
careful with airing aluminum down too far.. it doesn't like to bend back 
with a hammer and drift like steel does) due to the (generally) soft surface.

If I were doing nothing but rocks, I'd probably go to 20 to 25psi.. 
though again, I probably *could* run 15psi if I were crawlin' and 
finessin' around Moab (which, with my current gearing, isn't as pretty as 
I'd like.. should get that lower geared Dana 20 put together soon.. 
definitely before the Moab trip this spring).

If I were doing JUST mud?  I probably wouldn't touch tire pressure.  
Again.. depends on how thick and deep.. maybe I could try floating on 
thick mud.. in which case, low pressure is the way to go.. but if there's 
anything solid inside that mudhole and/or no change of floating, I don't 
want to slam into a big rock with low pressure... and dent the rim or 
something else.

Also, with my on-board air setup, I'm not so afraid to go down in 
pressure.. if I go too far, I just air it back up!

I used to run 35psi on the street and 20-25psi on the trail with my 
31x10.50s... if that helps much.

You can go a little lower in the rear due to less weight bouncing on the 
tires.

If you're running your 31x10.50s on a 15x10, you can't go as low as if 
you ran a 15x8 or 15x7.. since you'll have less bead-retention and blow 
beads.  My 33x12.50s are mounted on 15x8s... odds of me blowing a bead 
are slim... unless I'm racing and taking corners fast... (which, BTW, is 
stupid on low pressure.. you'll roll the bead right off.. oops)


Lower is better.  But tire pressure is a 'black art'... and falls into 
the "Stick vs. auto" and "Detroit vs. ARB" and "Jeep vs. LandCruiser" 
debates..

-Tom Mandera, Helena MT
http://www.tmcom.com/~tsm1/scout
New 1999 President of Frontier 4x4 (Hey, Theresa, we should get together..)