Tire pressure - 21" rims

[Sean Jones]

I'll start by saying I never check my tire pressure. My bad, just never do. Anyways out of curiosity I checked what they were at according to the in vehicle gauge. Cold, they were 3 with 30 psi and 1 was 31 psi. I checked the door jamb and recommended pressure is 35 psi. So 3 questions. Does everyone with these rims and tires maintain the 35 psi? And at what psi would the car tell they are low? Is the 30 psi really bad for the tires?

 

Thanks!

[akirby]

The warning doesn't go off until they're 25% low or around 27 psi. 30 is low but probably ok for a short period. Don't run less than 35 (on purpose). Some run 37-40.

[Sean Jones]

The warning doesn't go off until they're 25% low or around 27 psi. 30 is low but probably ok for a short period. Don't run less than 35 (on purpose). Some run 37-40.

Thanks for the fast response!!

[Sean Jones]

Maybe that is why was gas mileage seems to be lower lately too. Dummy me!

Edited July 14, 2017 by Sean Jones

[enigma-2]

Better to run at 36 than 34. 30 is too low, not only more rolling resistance but tires prematurely wear more on the edges and not as much in the center. At 15% low (30 psi vs. 35 psi) they will also be running hotter than normal, reducing life. Overheating can lead to tread separation.

Low tie presource also reduces carrying capacity.

 

Also, don't forget to check your spare. It may be low just when you need it most.

 

On my spare it reads to "inflate to 60 psi". However the owners manual states to inflate it to what the other 4 require. (?). The owners manual governs.

 

One last thought. My door sticker shows the pressure for 18" tires, what came with the car from the factory. After taking delivery, the first owner opted to put on 20" tires. (Still within Lincoln requirements). Therefore I have to go to the owners manual for recommendated pressures. Make certain tat the door sticker is for your exact tires, else check the OM.

[Sean Jones]

Thanks for the info! I really never had paid too much attention before, but these tires are expensive! I've put in in Google calendar to check them monthly from now on.

[1004ron]

On 7/13/2017 at 11:03 PM, enigma-2 said:

On my spare it reads to "inflate to 60 psi". However the owners manual states to inflate it to what the other 4 require. (?). The owners manual governs.

Old thread, but another thread prompted me to check my spare and it was at 21 psi.

 

My manual sates:

Quote

Note: Some spare tires operate at
a higher inflation pressure than the
other tires. For T type mini-spare
tires, see the Dissimilar Spare
Wheel and Tire Assembly section.
Store and maintain at 60 psi
(4.15 bar). For full-size and
dissimilar spare tires, see the
Dissimilar Spare Wheel and Tire
Assembly Information section.
Store and maintain at the higher of
the front and rear inflation pressure
as shown on the Tire Label.
 

 

Edited February 28, 2020 by 1004ron

[PSREDGE]

On 7/13/2017 at 9:56 PM, Sean Jones said:

I'll start by saying I never check my tire pressure. My bad, just never do. Anyways out of curiosity I checked what they were at according to the in vehicle gauge. Cold, they were 3 with 30 psi and 1 was 31 psi. I checked the door jamb and recommended pressure is 35 psi. So 3 questions. Does everyone with these rims and tires maintain the 35 psi? And at what psi would the car tell they are low? Is the 30 psi really bad for the tires?

 

Thanks!

 

 

You need to periodically check your tires - say once a month, with a reliable gauge. Recommended TP is 35 psi as shown on the driver door jam. Running those tires at 30 psi is under inflated. At that time low pressure the edges of the sidewalls will run on the ground, evidenced by dirt on the very edged. Inflate them to 35 psi when cold. After a few miles the pressure will rise as the. Tires heat. Do not bleed off that extra pressure. When cold tire pressure will to normal.   PSREDGE 

[omar302]

3 hours ago, PSREDGE said:

Does everyone with these rims and tires maintain the 35 psi? And at what psi would the car tell they are low? Is the 30 psi really bad for the tires?

1- I do.

2- I remember it around 27-28 psi for the warning to illuminate.

3- At 30psi, tires will probably wear on the edges noticably more than the center. Also it would have a small effect on fuel consumption.

[todd92]

If you switch tire sizes, you must calculate the new recommended pressure vs this door jamb sticker number according to this guide.  As the load rating goes up, the required tire pressure goes down.

 

Tire Inflation.pdf

[1004ron]

On 7/13/2017 at 9:56 PM, Sean Jones said:

Does everyone with these rims and tires maintain the 35 psi?

 

14 hours ago, omar302 said:

1- I do.

I do as well, and I find the dashboard pressure indication to be accurate and check it at least once a week and if it drops one or two psi, I top it up with my home compressor using an inflater with an accurate gauge.