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Tire Pressure Adjustments and Customer Satisfaction
Vehicles equipped with a Tire Pressure Monitoring System (TPMS) periodically monitor the air pressures in each
tire. The TPMS informs (via the TPMS light) the customer of low tire pressure when the tire pressure is 6 psi (+/-
2 psi) below the cold tire placard pressure.
The air pressure in each tire depends on several factors; one of them being the temperature of the air inside the
tire. As the air temperature inside the tire increases, the air pressure also increases. While driving in a normal
manner, a typical tire may increase approximately 2 to 4 psi in inflation pressure from a cold start situation. This
increase in tire pressure is a direct response to an increase in the air temperature. The air temperature depends on
several factors, such as, rate of tire rotation, tire deflection, amount of braking, etc.
In a similar way, tire pressure decreases if the contained air temperature decreases. For example, if the vehicle is
stationary overnight with the outside temperature significantly lower than the daytime temperature, the tire
pressure may decrease approximately 3 psi for a drop of 30° F in ambient temperature. This lower pressure value
may be detected by the TPMS as being significantly lower than the cold pressure specification, and thus, activates
the TPMS warning system for low tire pressure. If the low tire pressure warning light has been set, check and
inflate all road tires to the cold tire pressure specification which is recommended for this vehicle. Tire pressure
adjustment may be required during colder months of the year.
•
Use the following table to adjust tire pressure when your shop temperature is greater than the outside
temperature.
– This chart assumes that shop temperature is 21º C (70º F).
Tire Pressure Setting Adjustment Chart
Certification
Label Pressure
(psi)
30
32
34
36
38
40
40
44
46
48
50
2004 Explorer/Mountaineer New Model Technician Training
This chart assumes shop temperature is 21º C (70º F).
Outside Ambient Air Temperature (Degrees F)
-10
0
10
37
36
35
39
38
37
41
40
40
44
43
42
46
45
44
48
47
46
48
47
46
53
52
51
55
54
53
57
56
55
60
59
57
LESSON 4: ELECTRICAL
20
30
40
Adjust Tire Pressure To:
34
33
33
36
36
35
39
38
37
41
40
39
43
42
41
45
44
43
45
44
43
50
48
47
52
51
49
54
53
52
56
55
54
12-AUG-03
50
60
70
32
31
30
34
33
32
36
35
34
38
37
36
40
39
38
42
41
40
42
41
40
46
45
44
48
47
46
50
49
48
52
51
50
4-11
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