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Tire pressures


SenorNoob

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4.0
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4WD
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1.5" Front + 4" Rear
Tire Size
245-70-R16
All good till you get one the newfangled things with the TPMS that insists 0.6PSI up or down on a single tire is dangerous. My sticks aren't that accurate.

I worked with a guy one time that ate off the floor cause he said the germs kept him from getting sick. Seemed to have worked for him. He didn't miss a day in a year. Freaked me out though when I dropped lasagna on the shop floor and he scraped it up and asked me if he could have it. The floor was so dirty that wiping the sauce up made a clean spot.
 


racsan

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ford/escape
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2.5 (4 Cylinder)
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2.5/151 I-4
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Automatic
2WD / 4WD
2WD
Tire Size
235/70/16
My credo
the grey-t escape
I hate tpms. The ranger is too old for it fortunately, the escape had its system damaged by ntb and is now disabled. The equinox has it, still works and shows each tire pressure when you are on a certain display screen. Guess the new car wont have a 2nd set of tires. I have 3 sets for the escape and 4 sets for the ranger. With 2” spacers I could even run the escape wheels on the ranger. yeah, “tiring” I know. lol
 

sgtsandman

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Ranger XLT/FX4
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4.0 SOHC/2.3 Ecoboost
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4WD
Total Lift
Pre-2008 lift/Stock
Tire Size
31X10.5R15/265/65R17
I generally don’t worry about it too much since the tires are known to hold air pressure pretty well.

So, they might get checked once a month unless there has been a big temperature change. A 30-40 degree change in temperature is not an unheard of thing here.

The 2011 is a little more touchy though. If the pressures go up to much, the handling gets squirrelly.
 

James Morse

1997 XLT 4.0L 4x4 1999 Mazda B3000 2wd
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Automatic
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Tire Size
31x10.5-15 K02's on the Ranger, 235/75R15 on Mazda
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The perfect is the enemy of the good.
28.6kwh per month. If I pay 10cents per kWh, that’s 2.86cents per month
um, I think 28.6 * $.1 = $2.86/month not 2.86 cents. correct me if I'm wrong.

As to pressures, if they warm up after a mile or so, isn't -that- the pressure you're really interested in? since that's what's there under use?
I appreciate the tables and add'l info on it.
I've yet to try airing down for off road but want to try it. I didn't have any issues going places (if clearances were ok) but it can get bumpy as all get out so if it softened the ride a little, that would be nice.
Right now I've been running 31 psi all around (at 70F), I'll probably have to add a bit as the weather cools. And I'll do another water test to check tread contact, but I think it's good, and it drives nice on the highway, neither heavy steering (admittedly power steering may disguise that some were it there) nor wandering, feels nice and secure. Loving the K02's. Real quiet on the road but lots of grip for off road. They do collect some gravel in the tread and you hear it coming off when you get back on the road at speed. Ping.
So it means under driving, they're probably a bit higher psi than at 70F but whatever it is, seems good, I could measure them warm just for s/g.
I agree with the approach to find what drives nice and has good contact patch and assume that whatever it is at the ambient air measurement it'll be slightly higher in actual use; but no need to overthink it, unless you find it drives weird or you see uneven wear.
 

ericbphoto

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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.
um, I think 28.6 * $.1 = $2.86/month not 2.86 cents. correct me if I'm wrong.
You got me there. But with LED's, it's still an inconsequential number.
 

sgtsandman

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Total Lift
Pre-2008 lift/Stock
Tire Size
31X10.5R15/265/65R17
um, I think 28.6 * $.1 = $2.86/month not 2.86 cents. correct me if I'm wrong.

As to pressures, if they warm up after a mile or so, isn't -that- the pressure you're really interested in? since that's what's there under use?
I appreciate the tables and add'l info on it.
I've yet to try airing down for off road but want to try it. I didn't have any issues going places (if clearances were ok) but it can get bumpy as all get out so if it softened the ride a little, that would be nice.
Right now I've been running 31 psi all around (at 70F), I'll probably have to add a bit as the weather cools. And I'll do another water test to check tread contact, but I think it's good, and it drives nice on the highway, neither heavy steering (admittedly power steering may disguise that some were it there) nor wandering, feels nice and secure. Loving the K02's. Real quiet on the road but lots of grip for off road. They do collect some gravel in the tread and you hear it coming off when you get back on the road at speed. Ping.
So it means under driving, they're probably a bit higher psi than at 70F but whatever it is, seems good, I could measure them warm just for s/g.
I agree with the approach to find what drives nice and has good contact patch and assume that whatever it is at the ambient air measurement it'll be slightly higher in actual use; but no need to overthink it, unless you find it drives weird or you see uneven wear.
The industry standard is to check the tires when cold as being best practice for the most accurate reading since there are too many variables to account for when driving. Yest, the tire pressure will go up while driving but not by a whole lot, usually. About 1 to 2 psi on average and is not a concern since there is a buffer built into the capability of the tires by the tire manufacturer. Like many things, the tires are generally under rated for a built in safety factor because what should happen and what does happen in the real world are two very different things.

As far as tire pressures for off road, what you are driving on will dictate what is generally best for traction and rolling resistance. The lower the pressure, the higher the rolling resistance will be and thus more fuel will be used. So it's a balancing act.

Here is the numbers I use for my Rangers and my utility trailer. These numbers are generally agreed upon by experienced off roaders and overlanders for non-bead locked tires. Focus on the percentages and not the psi numbers I am using. Each vehicle is different. So the numbers you end up with may be different. The one caution I would make is to not go below 15 psi with a non-bead locked tire. You could end up with a bead separation.

HOW LOW CAN YOU GO?

Just how much do you air down? Obviously, it depends on conditions, but also on the normal street pressure you run, which might be 35 psi in a Tacoma, or 65 in a 9,000-pound Sports mobile on big E-rated tires.

25%

Trailer – 26 psi

2011 Ranger – 27 psi

2019 Ranger – 23 psi


As a (very) rough guide, dropping pressure about 25 percent will significantly increase traction and comfort on rough dirt roads, washboards, and moderate trails.

30-35%

Trailer – 25 to 23 psi

2011 Ranger – 25 to 23 psi

2019 Ranger – 21 to 20 psi


Dropping 30 to 35 percent elongates the tire’s footprint enough to enhance grip on slick rock, and allows it to deform around and cling to big rocks.

50%

Trailer – 18 psi

2011 Ranger – 18 psi

2019 Ranger – 15 psi


Heading down to 50 percent, even a bit less, will nearly double the length of the contact patch to float over very soft sand.
 

ericbphoto

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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.
The ratings you read in the sidewalls and door sticker are COLD ratings. They are designed to account for heating up during use. I believe the posted ratings even say the work cold.
But really, these are approximate numbers. 1 psi or 0.1 psi or 0.01psi either way make no appreciable difference unless you are in a high speed high performance machine. And these trucks don’t come anywhere close to that scenario.
You’ll never have any fun if you spend your whole life fretting over tire pressure being exactly perfect for each scenario. Just put some air in and go drive the thing.
 

James Morse

1997 XLT 4.0L 4x4 1999 Mazda B3000 2wd
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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.
lol yup that's what I been doing so far. They started out 35 psi from the shop but it felt loose/wandery on the road so I went to 31, checked tread contact, and never looked back. When the weather turns colder I'll adjust them. This week it's in the 70's.
I'm going to try the air-down probably next time.
 

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