• Welcome Visitor! Please take a few seconds and Register for our forum. Even if you don't want to post, you can still 'Like' and react to posts.

Tire pressures


James Morse

1997 XLT 4.0L 4x4 1999 Mazda B3000 2wd
Supporting Member
Joined
Aug 31, 2021
Messages
1,891
Reaction score
973
Points
113
Location
Roanoke VA
Vehicle Year
1997 and 1999
Make / Model
XLT 4x4 & B3000
Engine Type
4.0 V6
Engine Size
4.0L in XLT, 3.0L in B3000
Transmission
Automatic
2WD / 4WD
4WD
Tire Size
31x10.5-15 K02's on the Ranger, 235/75R15 on Mazda
My credo
The perfect is the enemy of the good.
If I set my pressures at 31 psi @ 70F, when I measure them at 54 they are 29 psi. If I measure them with one side in the sun on a nice day, the sunny side is 33-34 psi (the other shady side, 31).

pv=nRT the gas laws. I'll leave it to someone else to figure out if my numbers above make sense - given they are just approximate - for example if air is 54F and it was a cold night tires could be colder.

In the gas laws equation for this purpose, volume doesn't change (unlikely the tire balloons/stretches out), only temp and pressure change in a well known relationship.

The point is, you can set your pressures whatever you like in the shop in known conditions, but to really know what they are it would be necessary to measure (and set, presumably) them just before actual use. For off road this wouldn't be a big deal because you could well be airing down/up so you'd do it within the immediate conditions. For normal driving, normally you don't check them all the time, however, I think we all can agree that if you're in a summer/winter climate and you set your tires good at 20F, when it's 80F it's not going to read the same and iirc we always let air out in the spring/summer and put air back in the winter.

A friend of my dad's, who we kind of made fun of at the time for doing it, without fail walked around his car before he got in to see, do the tires look good. Turns out this is actually smart, because if you just get in and start driving on a flat or low-pressure tire when you could have just fixed/aired it at home, you pay the price in various ways. It takes just a couple seconds to check both sides. That was in the 60's, and it seems like we had a lot more flats then, but it's still a good habit.
 


sgtsandman

Aircraft Fuel Tank Diver
TRS Forum Moderator
U.S. Military - Active
TRS 20th Anniversary
TRS Event Participant
Ham Radio Operator
GMRS Radio License
Joined
Mar 11, 2017
Messages
12,451
Reaction score
12,033
Points
113
Location
Aliquippa, PA
Vehicle Year
2011/2019
Make / Model
Ranger XLT/FX4
Engine Size
4.0 SOHC/2.3 Ecoboost
2WD / 4WD
4WD
Total Lift
Pre-2008 lift/Stock
Tire Size
31X10.5R15/265/65R17
The general rule of thumb is that tires gain or loose about 1 psi for every 10 degrees of temperature change.

Tires in the sun and in the shade will complicate that greatly.

The best you can do is check your tires when there has been a big temperature change.

You also don’t want to do that within three hours of driving for more than about a mile because the tires warming up from driving will throw the psi off as well.

It can be a deep rabbit hole to dive into, if you let it, and will drive someone with OCD about it crazy. A couple psi off isn’t a huge deal. Once you get to 5 psi or more, I would worry and correct it.
 

mikkelstuff

Well-Known Member
U.S. Military - Veteran
Joined
Mar 26, 2018
Messages
593
Reaction score
438
Points
63
Location
Brighton, CO
Vehicle Year
2002
Make / Model
Ford
Engine Type
3.0 V6
Engine Size
3.0L
Transmission
Automatic
2WD / 4WD
4WD
I use this table generated for 35 psig tire pressure at 70 deg F and assuming a tire, near full, to be of constant volume.

tire_pressure.jpg
 

RobbieD

2.9l Mafia
Joined
Aug 6, 2007
Messages
3,586
Reaction score
2,942
Points
113
Location
Georgia
Vehicle Year
1984,1990,1994
Make / Model
Ford
Transmission
Manual
2WD / 4WD
2WD
My credo
Toonces drives a Ranger . . . . just not very well.
You guys worry to much
You mean that you don't lay awake at night, wondering if the light in the refrigerator really DIDN'T turn off when you closed the door?
 

rusty ol ranger

Im a Jeep guy now.
Supporting Member
Joined
Sep 22, 2007
Messages
12,092
Reaction score
7,068
Points
113
Location
Michigan
Vehicle Year
1987
Make / Model
Ford
Engine Type
2.9 V6
Engine Size
177 CID
Transmission
Manual
2WD / 4WD
2WD
My credo
A legend to the old man, a hero to the child...
You mean that you don't lay awake at night, wondering if the light in the refrigerator really DIDN'T turn off when you closed the door?
Nope.

I do visually check tire pressure...or if its driving goofy...but generally i set em and forget em.
 

ericbphoto

Overlander in development
TRS Event Staff
TRS Forum Moderator
Supporting Member
U.S. Military - Veteran
TRS 20th Anniversary
VAGABOND
TRS Event Participant
GMRS Radio License
Joined
Feb 7, 2016
Messages
14,987
Reaction score
15,979
Points
113
Age
59
Location
Wellford, SC
Vehicle Year
1993
Make / Model
Ford Ranger
Engine Type
3.0 V6
Engine Size
3.0L
Transmission
Manual
2WD / 4WD
4WD
Total Lift
6"
Tire Size
35"
My credo
In theory, theory and practice are the same. In practice, they are different.

ericbphoto

Overlander in development
TRS Event Staff
TRS Forum Moderator
Supporting Member
U.S. Military - Veteran
TRS 20th Anniversary
VAGABOND
TRS Event Participant
GMRS Radio License
Joined
Feb 7, 2016
Messages
14,987
Reaction score
15,979
Points
113
Age
59
Location
Wellford, SC
Vehicle Year
1993
Make / Model
Ford Ranger
Engine Type
3.0 V6
Engine Size
3.0L
Transmission
Manual
2WD / 4WD
4WD
Total Lift
6"
Tire Size
35"
My credo
In theory, theory and practice are the same. In practice, they are different.
You mean that you don't lay awake at night, wondering if the light in the refrigerator really DIDN'T turn off when you closed the door?
No. It’s plugged into an AC source. It won’t run the battery down. A 40watt incandescent appliance bulb operating 24 hrs a day = 960 watt-hours or 0.96kilowatt-hours. .96kwh x 30 days = 28.6kwh per month. If I pay 10cents per kWh, that’s 2.86cents per month. But my refrigerator has an LED bulb that draws a small fraction of that. So, let it burn, baby! Let it burn!
 
Last edited:

RobbieD

2.9l Mafia
Joined
Aug 6, 2007
Messages
3,586
Reaction score
2,942
Points
113
Location
Georgia
Vehicle Year
1984,1990,1994
Make / Model
Ford
Transmission
Manual
2WD / 4WD
2WD
My credo
Toonces drives a Ranger . . . . just not very well.

rusty ol ranger

Im a Jeep guy now.
Supporting Member
Joined
Sep 22, 2007
Messages
12,092
Reaction score
7,068
Points
113
Location
Michigan
Vehicle Year
1987
Make / Model
Ford
Engine Type
2.9 V6
Engine Size
177 CID
Transmission
Manual
2WD / 4WD
2WD
My credo
A legend to the old man, a hero to the child...
Y'all are missing the point- the turkey can't sleep with the light on.

Tired turkey is tough, and tastes terrible.
Turkey is always good
 

RobbieD

2.9l Mafia
Joined
Aug 6, 2007
Messages
3,586
Reaction score
2,942
Points
113
Location
Georgia
Vehicle Year
1984,1990,1994
Make / Model
Ford
Transmission
Manual
2WD / 4WD
2WD
My credo
Toonces drives a Ranger . . . . just not very well.
Turkey is always good
Until it's not. Let it sit in the fridge for about a month; green turkey that glows in the dark has stopped being a health food.
 

rusty ol ranger

Im a Jeep guy now.
Supporting Member
Joined
Sep 22, 2007
Messages
12,092
Reaction score
7,068
Points
113
Location
Michigan
Vehicle Year
1987
Make / Model
Ford
Engine Type
2.9 V6
Engine Size
177 CID
Transmission
Manual
2WD / 4WD
2WD
My credo
A legend to the old man, a hero to the child...
Until it's not. Let it sit in the fridge for about a month; green turkey that glows in the dark has stopped being a health food.
Scrape the maggots off and chow down. Dont be a sis :ROFLMAO:
 

Uncle Gump

Token Old Guy
TRS Event Staff
TRS Forum Moderator
Supporting Member
VAGABOND
TRS Event Participant
Joined
Sep 17, 2018
Messages
13,422
Reaction score
12,839
Points
113
Location
Ottawa IL
Vehicle Year
2006/1986
Make / Model
Ranger/BroncoII
Engine Size
4.0L SOHC/2.9L
2WD / 4WD
4WD
My credo
Lead follow or get out of my way
I shoulda sent rusty that container of spaghetti I found today cleaning out the fridge.
 

gaz

Well-Known Member
U.S. Military - Veteran
Joined
Sep 21, 2007
Messages
1,352
Reaction score
602
Points
113
Location
Wa, Bremerton 98310
Vehicle Year
1987
Make / Model
Ford
Engine Size
87Ranger Endrigo 2.9l, 87BII Endrigo 4.0l
2WD / 4WD
4WD
Total Lift
Ranger 5" (1.5" suspension), BII 4" suspension
Total Drop
Ranger 5sp, BII A4LD
Tire Size
Ranger 33"/4:10LS, BII 29"/3:73LS
My credo
Deengineer until it is how Blue Oval should have sold it!!
@James Morse ,
I drive to the air station, air them all to 32. I verify the pressure with my cool-guy digital pressure gauge and call it a day.

After a 10 mile drive the tires are all nearly the same temperature, the air station is covered, never in the sun. It isn't perfect but it is as consistent as I can reasonably manage without making it a hobby or third job 🙃
 

rusty ol ranger

Im a Jeep guy now.
Supporting Member
Joined
Sep 22, 2007
Messages
12,092
Reaction score
7,068
Points
113
Location
Michigan
Vehicle Year
1987
Make / Model
Ford
Engine Type
2.9 V6
Engine Size
177 CID
Transmission
Manual
2WD / 4WD
2WD
My credo
A legend to the old man, a hero to the child...

Sponsored Ad


Sponsored Ad

Staff online

Member & Vendor Upgrades

For a small yearly donation, you can support this forum and receive a 'Supporting Member' banner, or become a 'Supporting Vendor' and promote your products here. Click the banner to find out how.

Truck of The Month


Yotaismygame
February Truck of The Month

Recently Featured

Want to see your truck here? Share your photos and details in the forum.

Follow TRS On Instagram

TRS Events

Check Out The TRS Store


Sponsored Ad


Sponsored Ad

Sponsored Ad


Amazon Deals

Top