Tire pressure thread #many

[RobertFord]

Hi All,

After doing a lot of searching on this forum about the appropriate tire pressure.

I am using the formula as described a lot on the internet
Tire_pressure_in_Bar = Maximum_tire_pressure_in_bar * (Actual_weight_on_tire_in_kg/Maximum_weight_on_tire_in_kg) ^ 1.25

The door panel on my X says front weight is 1152kg, and rear is 1338kg.
I'm running some old kind of tire on the front, maximum weight 920kg, pressure 35PSI. The rear are relatively new Bridgestone Dueler A/T 964's, maximum weight 975kg, maximum pressure 44PSI. (Was actually not on the tire? had to look it up)

So, using the famous formula, I ended up with advised pressure of 1.34 bar (19.49 PSI) on the front and 1.89 bar (27.48 PSI) on the rear.

I'm somewhat shocked by these outcomes. (Also, as I had apparently been pressurising my front tire very near the maximum allowed) and am somewhat worried about it. I can't possibly rock 1.34 and 1.9 bar on these tires, right? The front is even lower than Fords famous rollover pressure of 26 psi.

Any insights/recommendations?

As I entered it into excel:

Variable	Description		Front	Back	Formula
A_psi	Actual Tire pressure (psi)	19.49	27.48	=A_bar/0.0689476
A_bar	Actual Tire pressure (bar)	1.34	1.89	=B_bar*(C_kg/D_kg)^1.25
B_psi	Maximum tire pressure (psi)	35	44	
B_bar	Maximum tire pressure (bar)	2.41	3.03	=B_psi*0.0689476
C_lbs	Actual weight on the tire (Lbs)	1270	1475	=C_kg*2.20462262
C_kg	Actual weight on the tire (KG)	576	669	
D_lbs	Maximum tire load (Lbs)		2028	2150	=D_kg*2.20462262
D_kg	Maximum tire load (KG)		920	975

 

[Jason94sport]

WAY too low. Set them at 32-35psi & leave it.

 

[arco777]

91-94 Explorer:

For a 4x4 you want 30psi up front, 35psi in the back.
For a 4x2 you want 28psi all around, I believe. The only 2WD I had was a 2-door model and I'm not sure if the 4-door pressures differed.

It's on the door sticker.

 

[safn1949]

I run 35psi all around,helps a little with fuel mileage and these trucks(1rst gen 4x4) ride like a freight train anyway.I have decent tire wear from the crappy Goodyear P rated tires I have.

Gotta get some LT tires.

 

[Maniak]

What you calculated is the absolute minimum pressure to carry that weight, not what you should run. A chalk test is really the only way to find the right pressure.

~Mark

Hi All,

After doing a lot of searching on this forum about the appropriate tire pressure.

I am using the formula as described a lot on the internet
Tire_pressure_in_Bar = Maximum_tire_pressure_in_bar * (Actual_weight_on_tire_in_kg/Maximum_weight_on_tire_in_kg) ^ 1.25

The door panel on my X says front weight is 1152kg, and rear is 1338kg.
I'm running some old kind of tire on the front, maximum weight 920kg, pressure 35PSI. The rear are relatively new Bridgestone Dueler A/T 964's, maximum weight 975kg, maximum pressure 44PSI. (Was actually not on the tire? had to look it up)

So, using the famous formula, I ended up with advised pressure of 1.34 bar (19.49 PSI) on the front and 1.89 bar (27.48 PSI) on the rear.

I'm somewhat shocked by these outcomes. (Also, as I had apparently been pressurising my front tire very near the maximum allowed) and am somewhat worried about it. I can't possibly rock 1.34 and 1.9 bar on these tires, right? The front is even lower than Fords famous rollover pressure of 26 psi.

Any insights/recommendations?

As I entered it into excel:

Variable	Description		Front	Back	Formula
A_psi	Actual Tire pressure (psi)	19.49	27.48	=A_bar/0.0689476
A_bar	Actual Tire pressure (bar)	1.34	1.89	=B_bar*(C_kg/D_kg)^1.25
B_psi	Maximum tire pressure (psi)	35	44	
B_bar	Maximum tire pressure (bar)	2.41	3.03	=B_psi*0.0689476
C_lbs	Actual weight on the tire (Lbs)	1270	1475	=C_kg*2.20462262
C_kg	Actual weight on the tire (KG)	576	669	
D_lbs	Maximum tire load (Lbs)		2028	2150	=D_kg*2.20462262
D_kg	Maximum tire load (KG)		920	975

 

[RobertFord]

What you calculated is the absolute minimum pressure to carry that weight, not what you should run. A chalk test is really the only way to find the right pressure.

~Mark

Great! Thanks a bunch!