How much to air down?... 315/75r16 on 16x8

[Shooter307]

Wanted to re-adjust my tire deflators the other day but wasn't sure how low to run them.

I searched a few times earlier but haven't found a great answer. I'm wondering what pressure people are having success airing down to on 315/75r16 tires on a 8" wide wheel for various surfaces - and/or how low is too low of a pressure before you can expect yourself to start breaking beads on the trail?

I used to have 285/75s on 16x7 Tacoma wheels and have gone down to as low as 12-13psi with no problems and I found that was somewhat of a magic number for me once a buddy pushed me to try them down that low.

One additional question that has been making me think: In general is one surface more likely to break beads than another? For instance serious snow wheeling sometimes requires very low pressures, would snow be more, less, or just as likely to break a bead compared to rocks or loose dirt?

 

[LandCruiserPhil]

I use 15psi as a starting (where my deflators are set) and go down from there. Never lost a bead on Toyota factory wheels and been down to 10 psi in sand more then once

 

[woody]

Hate to say it, but I cannot stand the auto-deflators...most are dependent on elevation and also assume you "always" want the same tire pressure. I use the ARB system and adjust based on where I'm wheeling.

20psi is a good starting point. I pretty much go where I want at that PSI. If I'm in Moab, I will drop to 18-19. Sand, a bit lower. SoDak, stay at 20.

Speed and sharp turns are mostly what roll beads off. Remember, the lower the air pressure, the more likely a hard turn at the bottom of the hill will roll to the rim edge...and the less precise your steering is.

Personally, 18-20 is the right compromise for me. (and with 10,000 users on 'MUD, expect 10,000 answers!)

 

[Shooter307]

Thanks for the input guys. And That's what I'm thinking woody, I previously set them at the upper range of what I use as a starting point so I can air down all 4 at once instead of one by one and I usually double check them with a gauge anyway. Didn't think about the elevation aspect though, very interesting.

 

[Tapage]

there are 2 keys for me ..

1. tire construction

2. speed and control

if you are wheeling a terrain ( like rocks ) you can always have control of your speed, then you can go low

 

[watrob]

Think you also have to allow for the side wall thickness of your tyre, the above photo I feel is a touch to low for the terrain and the weight of the vehicle, you may not loose a bead but that's pretty close to splitting or pinching a sidewall on rocks, specially as tyres age.

I run 8 ply and the lowest I have gone is 14-16psi but usually run 19psi on the beach.

 

[Hulsty]

10psi for general wheeling and higher speed stuff, 5psi when it get knarly