Michelin A/S PS4 pressure

[Beachybumm]

I have a M3 LR with PS4s. Last week, the tire pressure light went on, flagging one of my tires. Today, two others were flagged. Those three are all at 39 PSI. what is the proper inflation level in Los Angeles, where driving temperatures in the winter rarely go below 55 degrees?

 

[Big Dog]

the light is going on at 39 psi per the screen? (my light doesn't go on until 36 psi)

When are you measuring the 39? How accurate is your gauge?

Hint: pressure is temperature-dependent. PSI will change 1 degree with every 10 degrees Farenheight.

fwiw: I also live in SoCal and set my tires at 39 psi in the early morning, so they will normally run 40-41 my mid-day.

 

[Beachybumm]

the light is going on at 39 psi per the screen? (my light doesn't go on until 36 psi)

When are you measuring the 39? How accurate is your gauge?

Hint: pressure is temperature-dependent. PSI will change 1 degree with every 10 degrees Farenheight.

fwiw: I also live in SoCal and set my tires at 39 psi in the early morning, so they will normally run 40-41 my mid-day.

Yes, it's going off at 39. And I reset the one that went off last week without refilling because it went back up to 40. But then it (and two others) alerted today at 39.

I don't know what you mean by "when" are you measuring. It's whenever I get in my car. Also, how would I know the accuracy of the gauge?

 

[Kimmi]

How much did you pay for the gauge?

 

[Beachybumm]

What gauge? There's no gauge involved. The tire alert came on at 39 psi. I have never mentioned a gauge.

 

[tlr1000]

I think the only 'gauge' the OP is referring to is the factory TPMS sensor inside the wheel and the readings are the ones on the main screen of the car. Note external temp fluctuations and even the warming up of tires when driving all change the PSI. I have 19s and in a recent service visit, they put my tire pressure to 45 psi and the tech said it was the best balance for performance and tire wear. My door says 42psi but the tech said their current recommendation was 45psi. I'm guessing 18's would be similar in psi spec. Based on that, I suspect 39 psi must be the trigger point for the light to go on.

To resolve, I'd say just add a couple more psi so that any fluctuation happening doesn't dip below 40psi. You can also get tires nitrogen filled which will be much less sensitive to psi fluctuations from temperature changes.

 

[Big Dog]

Based on that, I suspect 39 psi must be the trigger point for the light to go on.

Unlikely, as Elon tweeted (awhile ago) that folks could fill their cars to 39 for more comfort. (it was in response to a lot of complaints about the harshness of the ride.)

https://twitter.com/elonmusk/status/1001903414555492352?lang=en

I think the only 'gauge' the OP is referring to is the factory TPMS sensor inside the wheel and the readings are the ones on the main screen of the car. Note external temp fluctuations and even the warming up of tires when driving all change the PSI.

Agreed. OP you need to spring for a high quality gauge to check your tires cold at home, before driving anywhere.. (plenty of threads on good inexpensive gauges.) Also get an air pump and charge to 42 while cold.

My door says 42psi but the tech said their current recommendation was 45psi.

Sure, but what you gain in range you lose in 'comfort'. (or some do, as others prefer the harder ride)

Regardless, if your door says 42 psi, the warning light should not go on at 39, since that is <10% change from the OEM recommended. (my wife's car also says 42, and her warning light does not go on until 36.)