How to calculate air down pressure

[NJTramcar]

I have a 6 cyl, 2012 Toyota 4Runner.

 

How do I figure out what pressure to air down to?  Is there a formula?

[SC]

May no longer be an accurate or relevant method but starting with cold tires I was taught to air down on a paved surface till sidewall buckled then add two pounds

[RedJeep]

You are trying to make your foot print bigger so I would agree with SC. However if it is pouring down rain you can seldom go wrong. And when there has been no rain for the last month you may have to go lower. And if you try to pull some thing or someone, forgettabout it.

 

Peace

[Captain Planet]

I do 20lb on my 4Runner.  

Has not let me down.  If the sand is realllllly soft, I would go lower.

Really depends on your tire too.  They guys with E rated tires will have to get lower due to the stiffer sidewalls/plys.  

[NJTramcar]

Thank you all for the info.

 

Captain, I have Cooper Discover AT 265/70R17 with 44 PSI.  Not an E tire.

[Highlander1]

20 is probbaly ok, 15 works best for most vehicles. The less strain on the engine and trans is what your looking for, ideally bald almost flat tires work best.

[Captain Planet]

Start with 15/20.  If you feel the truck isn't coasting well at all on the sand, maybe go lower.

Basically if you take your foot off the gas, you don't want to immediately sink and lurch to a halt.  You want a little bit of saved momentum.  

Edited May 12, 2021 by Captain Planet

[Stryper Snyper]

3 hours ago, NJTramcar said:

I have a 6 cyl, 2012 Toyota 4Runner.

 

How do I figure out what pressure to air down to?  Is there a formula?

No need for a formula.  Small light vehicle like that.  18-15 psi.  Don't drive like a mad man you're good to go.   And out of curiosity why are you running such high pressure? 

[NJTramcar]

1 hour ago, Stryper Snyper said:

No need for a formula.  Small light vehicle like that.  18-15 psi.  Don't drive like a mad man you're good to go.   And out of curiosity why are you running such high pressure? 

That's the max PSI stamped on the tire.

[Stryper Snyper]

9 mins ago, NJTramcar said:

That's the max PSI stamped on the tire.

You should look at the recommended pressure on the sticker by the door jamb.   Guessing 32ish.   Yeah will increase MPG a bit. But gonna kill the tires.

[NJTramcar]

1 min ago, Stryper Snyper said:

You should look at the recommended pressure on the sticker by the door jamb.   Guessing 32ish.   Yeah will increase MPG a bit. But gonna kill the tires.

Thanks, good to know.

[Capt Buck]

1 hour ago, NJTramcar said:

That's the max PSI stamped on the tire.

Read the rest of the stamping on the tire. max PSIG is at a load. For example, a tire maybe rated for 3450 lbs load at 44 psig, This would mean the vehicle would have to have a weight of 13,800 lbs. to require max pressure. 

Your base curb weight of the Forerunner is 4400 lbs and probably rides like a basketball at 44 psig not to mention handle like a Teflon pan on ice on a pile of owl snot in the rain.

I've been playing with oversize tires for about 45 years and for me the chalk method has worked well for arriving at a good  highway pressure.

Go to a paved parking area, mark across the tread with the chalk, run back and forth and keep doing it with new chalk marks until the it is erased from the width of the tread. Adjust as needed to fit your driving habits.

Beach running most places say start at 18 psig, this depends on the beach. In Brigantine I would not air down any, the same with the Wildwoods. Hatteras it's right to 16 lbs with having to go to 12 sometimes

 

Heed other advice above as well, it's all good

As always, YMMV

 

Edited May 13, 2021 by Capt Buck

[Capt Buck]

For your edification while reading the above

[z-man]

7 hours ago, NJTramcar said:

Thank you all for the info.

 

Captain, I have Cooper Discover AT 265/70R17 with 44 PSI.  Not an E tire.

That’s way too much PSI for a 4Runner. It’s supposed to be 32 PSI. Air down to 18 psi for the beach if it’s relatively packed sand. If it’s deep soft sand go down to 12 psi. Keep it in 4WD high and you’ll be fine.