Proper tire inflation of F-150 pulling Cougar 22 MLS

[jadatis]

For 4wh drive is important that rolling circumference is about the same on all wheels.
So if for instance more weight on rear wheels, it gives more deflection then front, with same pressure. More deflection makes the rolling circumference ( the distance tire makes at 1 rotation) gets a bit smaller, so not ideal for 4wh drive .

So its better to give the pressure belonging to the load on tire, for the drivetrain.
Then deflection front and rear the same , and with that rolling-circumference.

Indirect tpms , wich uses rotation sensors from ABS , use the fact that rolling circumference gets shorter on a to low pressure tire, so more rotations per second.

 

[flybouy]

For 4wh drive is important that rolling circumference is about the same on all wheels.
So if for instance more weight on rear wheels, it gives more deflection then front, with same pressure. More deflection makes the rolling circumference ( the distance tire makes at 1 rotation) gets a bit smaller, so not ideal for 4wh drive .

So its better to give the pressure belonging to the load on tire, for the drivetrain.
Then deflection front and rear the same , and with that rolling-circumference.

Indirect tpms , wich uses rotation sensors from ABS , use the fact that rolling circumference gets shorter on a to low pressure tire, so more rotations per second.

I would like to see the evidence that a tire with more "squat" has a different rolling DISTANCE than one with proper inflation. The tread circumfrance would be identical. The only difference would be how much of the tread is in contact on the pavemer regardless of the shape.

You= prior post with the extensive inflation chart is confusing not very useful for trailer tires or tow vehicle tires in the USA. The tire inflation stickers that are mandated by Federal Law should should be the guide for minimum inflation pressure and the max should not exceed the rating on the tire sidewall.

 

[Cajun Couple]

20 yrs ago I had a Edge programmer that I needed to use a "squish factor" to change for tire heights. Only accepted millimeters for the circumference. Needed to get Al Einstein to help me out!!

 

[jadatis]

I would like to see the evidence that a tire with more "squat" has a different rolling DISTANCE than one with proper inflation. The tread circumfrance would be identical. The only difference would be how much of the tread is in contact on the pavemer regardless of the shape.

You= prior post with the extensive inflation chart is confusing not very useful for trailer tires or tow vehicle tires in the USA. The tire inflation stickers that are mandated by Federal Law should should be the guide for minimum inflation pressure and the max should not exceed the rating on the tire sidewall.

For agricultural tires they sometimes give rolling-circumference, and its not diameter x pi, but x 3.00 to 3.05. So tiremakers use it, and some youtube films prove it in practice.

But normal cartyres have lesser deflection, so RC about 3.05 to 3.10 x diameter or about 97% of circumference.

Many calculators on internet yust calculate diameter x pi, and for comparison thats pretty right.

Then where is the missing piece of treath ?
My theory is that yust before and right after the treath is on the ground, the treathsegment moves backward to the ground.
Been buisy with making a video about it once, to prove it.

And my made cold pressure/ axleload list leads to higher pressure then the official lists, so never unsaver for the tires.

 

[flybouy]

Tractor tires? We don't pull campers with farm equipment down the highway here in the states.

 

[Peto]

Actually it does change those things, it REDUCES them! Any added weight to the vehicle that was not in/on the truck the day it was manufactured deducts from the capacity ratings.

Is un-sprung weight included in the payload capacity? I'd assume only impact would be to Gross Vehicle Weight.

 

[NH_Bulldog]

Payload capacity is GVWR minus curb weight. Curb weight includes unsprung weight. Increase curb weight and your payload capacity is reduced by a corresponding amount.

Round numbers for example: A truck with a 10,000 lb. GVWR minus a curb weight of 7,000 lbs. gives a payload capacity of 3,000 lbs. Add heavier tires, an anti sway bar to the rear axle, airbags, etc. at around a collective increase of 100 lbs. and you increase the curb weight to 7,100 lbs. which subtracted from that 10,000 lb. GVWR gives you 2,900 lbs. payload capacity.

 

[Notanlines]

Payload capacity is EXACTLY as Bulldog described. No more complicated than that.

 

[hazmat456]

The door sticker give the proper inflation for the weight rated for the axle to carry. The pressure remains the same for every load range of that size tire. It changes very little for different size tires that would fit the same rims. The only reason to increase the pressures on stock size tires, regardless of load range, would be if you exceed your axle ratings.

 

[jadatis]

The door sticker give the proper inflation for the weight rated for the axle to carry. The pressure remains the same for every load range of that size tire. It changes very little for different size tires that would fit the same rims. The only reason to increase the pressures on stock size tires, regardless of load range, would b

The bolded part is to laws of nature not right.
For lighttrucks sometimes people change from standard load P-tires to E-load LT.
Then about 15 psi higher pressure needed to carry the same load.

In official lists in US the loadcapacity's are calculated for the pressures for one loadrange, and the other loadranges belonging referencepressures , the maxload of those loadranges replace the calculated values.
This gives strange yumps up or down , if you would make graphics of it.

In Europe, for every loadrange of same size tire, a seperate pressure/ loadcapacity- list is made.
If then graphics made of those list, it gives a fluid line .

If you would calculate maxload/ AT pressure, from for instance C- and E- load of same size LT or ST tire, the E-load has lesser lbs/psi then the C-load.

Example ST225/75R15
C-load 2150 lbs /50 psi = 43 lbs/ 1 psi.
D- load 2540 lbs/ 65 psi = 39.07 lbs/ 1 psi.
E-load 2830 lbs/ 80 psi = 35.38 lbs/ 1 psi.

 

[hazmat456]

 

[hazmat456]

 

[hazmat456]

inflation pressures are non liner. the formula is NOT x time psi = weight capasity

 

[jadatis]

People who calculate it lineair, are not doing it that bad.

End 2007 I got hold of the officially used european formula, and went running with it.
Became my rubber ducky. Later learned that in US different formula,s are used.

Will give an oversight.

European formula for every kind of radial tire, for decades used, and since 2006 also for P-tires in US.

Is loadcapacity= ( actual pressure/ referencepressure)^ 0.8 x maxload.
That ^0.8 is a power , like ^2 is square, and ^0.5 is root. On sciencetific calculators there is a button X^Y for it.
Gives a curved line in graphics.

Will give only power in universal formula formula ^X

X= 1 is lineair calculation
50% of referencepressure gives 50% of maxload as loadcapacity.

X= 0.8 the first mentioned gives at 50% of referencepressure, 57% of maxload.

X=0.7 used in US for LT and trucktires
Gives for 50% of Refpres, 61.5% of maxload.

X= 0,65 was used in US for P-tires with hight/width division below 50% upto 2006.
Gives at 50% of RP, 63.7% of maxload.

X= 0.585 was introduced in 1928 for diagonal tires, and still used for radial ST-tires.
50% pressure gives 66.66% of maxload.

X= 0.5 ( root) was used in US upto 2006 for radial P-tires with H/W division above 50%.
50% of pressure gives 70.7 % of maxload.

Draw your own conclusions if this is sound to laws of nature

 

[hazmat456]

On the right path, but each tire size requires a different formula because of the change in tire contact patch. Tire construction does not appear to be a factor among tires with the same basic design elements. A radial tire is a radial tire and the number of plies doesn't seem to factor into the math as long as the tire is rated to carry the given load.(A "G" rated tire will only carry 2700lbs at 50 psi which is the same as a "C" rated tire.) If the load is only 2700 lbs increasing the psi will only shrink the contact patch and compromise both braking and handling ability. The heavier tire will however resist blowouts and punctures better, and will be more heat tolerant. Thus more forgiving of inflation errors.

 

[jadatis]

Here picture of old lists, I got from Michelin, in the beginning of my tirepressure story.
Is in bar and kg axleload and german text, but only compare the values.

In that the 195/70R15 in C- and D- load with for D lower loadcapacity of 1300 kg axleload at 3 bar then the C-load 1338kg Both R speedrated.
Calculate with the ^0.8 formula, check it yourselves.

In US lists only one list for both , calculated for only for instance C-load , and then 4,5 bar ( 65 psi) overwritten by maxload of 1800 kg of D-load. And per tire given.

Also the 185R 15 , but one P and other R speedcode, but further same idea

 

[hazmat456]

View attachment 1068543
Here picture of old lists, I got from Michelin, in the beginning of my tirepressure story.
Is in bar and kg axleload and german text, but only compare the values.

In that the 195/70R15 in C- and D- load with for D lower loadcapacity of 1300 kg axleload at 3 bar then the C-load 1338kg Both R speedrated.
Calculate with the ^0.8 formula, check it yourselves.

In US lists only one list for both , calculated for only for instance C-load , and then 4,5 bar ( 65 psi) overwritten by maxload of 1800 kg of D-load. And per tire given.

Also the 185R 15 , but one P and other R speedcode, but further same idea

Looks like the lighter tire can carry more load than the heavier tire at the same pressure, which is exactly the opposite of what most people do when going up load ranges on their tires.
Ironically less pressure is needed with the heavier tire.
What most people tend to forget is the manufactures develop these figures to maintain the most contact with the ground. With that being said less pressure on the heavier tire makes sense. I think they have simplified the pressure charts and errored on the higher pressure side as a safety margin.
Then a customer buy the tire and adds an extra 10 psi, just to be safe, the tires now are only touching the ground in the center and loose traction.
Now the heavier tires have become less safe and wear faster.

 

[jadatis]

Gripp is not the main goal of tiremakers.
I had myself told by a man from Vredestein, that main goal is to not overheat any part of tire-material, when driving the speed constantly , for wich pressure is determined.
So for that a certain deflection is needed.
Goal of the lists is to give for lower then maxload , the tire the same deflection ( is my conclusion, assuming heatproduction goes lineair with deflection, but mayby not).

Now a higher loadrange tire of same size, is stiffer, to hold the higher pressure in.
This gives a larger overgoing curve from unloaded radius to flat on the ground.

This gives smaller surfacelength on the ground, at same deflection.
Has to be compensated by higher pressure to carry same load.

Once made an image with paint about the idea, in wich I supose the overgoing curve being part of circle, but mayby more complex curve.
For that reason the higher loadrange tire needs higher pressure for same load on it to give same deflection.
Or the other way around, has lower loadcapacity for the same pressure.

So if going to higher loadrange, and using the same pressure , as for OEM lower loadrange tire of same size, you risk more overheated tire. You yust need the by you mentioned example 10 psi more, to prevent overheated tires, driving the same speed.

 

[hazmat456]

Sorry this doesn't make any sence to me. Grip is a primary concern to manufacturers. The tire is designed around that. Sizing and construction is used to control heating concerns while maintaining grip. By your own chart less pressure is needed to maintain the same capabilities when switching to a higher load range. Higher pressure is only needed when a higher load is applied.

 

[jadatis]

It does not make sence to you, but this is lead by the expectations you have about it.

Do you mean my given list in post #36, or post #19.
In post #36 yust more pressure to maintain the same capability's , to use your own words.

The C-load 1336 kg at 3 bar, and the D load 1300 kg at 3 bar .
1 step higher 3.25 bar gives 1386 kg,
So yust a small difference , but this is because only going 1 loadrange higher.

In the SUV scene often stepped over from standard load P-tire AT 35 or 36 psi, to E-load LT AT 80 psi. And then about 15 psi higher needed then would be calculated for the GAWR .

But there often yust referencepressure of tire given ( 35 psi)as recomended pressure, and not calculated.
Those OEM tires often have comfortable reserves , so calculated for GAWR would give mayby 25 psi , then the D- load about 40 psi, and normal driving lower axleloads , so the 35 psi will still give no overheated tires.

Then those users in those forums will say, when I mention it, what are you nagging about Peter, 35 gives no problems with the E-loads. Untill they drive fully loaded or overloaded on the axle with higher speed.
Then overheated tire, wich gives beginning cracks, that tear further in time, untill mayby after 2 years that far , that tire blows or treath separates, and then the relation with that once overheating is long forgotten, and other factors are blamed, like Chinese brand.