New Model S 90D: Factory Tire Pressure / Sensor Oddity

[dvhart]

I took delivery on 2016-07-22 of my 2016 Model S 90D refresh. Yesterday the system warned me of low tire pressure for the rear right tire. It read as 37psi. I read the manual, then read the driver door label, which says 45psi for all tires. When cold, I inflated to 45psi and checked the dash. Only then did I realize I could see the psi of all four tires with the Car Status widget. I was surprised to find that the other three tires were inflated between 37 and 39 psi, while the rear right now read 45 psi, and the Low Tire Pressure warning light was now off. The car is not reporting a tire pressure sensor problem.

Is 45psi the correct tire pressure? This seems to be fairly obvious from the manual and door label. It does however seem odd that all 4 tires were set at ~38 psi from the factory, suggesting it was intentional.

 

[ecarfan]

45psi is the recommended tire pressure.

Keep in mind that different gauges will give different readings for the same tire, often quite different, more than 5 or even 10psi different. You are assuming that the TPMS sensors are perfectly accurate, or that the gauge used at the factory for checking pressures is perfectly accurate.

Also, temperature effects pressure.

 

[DCGOO]

The nominal pressure is highly dependent on ambient temperature. I set mine a little high (47 +/-) on a 90º+ day. Today at 75º they all were at 42.

 

[dvhart]

Ah, ambient temp explains it. Duh. I took delivery in 90+F weather, and temps just dropped significantly this week. Thanks! Will inflate to 42 or so as temps are still likely to spike again before the summer is out, but I suspect we're done with the 100+ days.

 

[Cstreet]

I got my car on 07-27 and just hit this same thing over the last week or so. First it was the right front then both on the left side. I inflated all the tires to 43 psi on a mild afternoon (72 degrees) and its been fine since.

 

[Redmiata98]

Fill your tires to the amount shown on the label. Make sure the car has set for awhile as the tires heat up when you use them, first thing in the morning before using after it has set overnight is when I do it. Once you have them all set at the same pressure, you will notice that they will adjust to the temperature and use frequently by a pound or two. Just parking the car with one side in the sun the other in shade will account for a difference in pressure.

Sometime there is also a difference in the required tire pressure between summer and winter tires. I experienced this difference with my S when changing between the two on my S. My Service Center contacted the factory and they provided two different inflation pressures that varied based on summer or winter tires.

 

[DCGOO]

Ah, ambient temp explains it. Duh. I took delivery in 90+F weather, and temps just dropped significantly this week. Thanks! Will inflate to 42 or so as temps are still likely to spike again before the summer is out, but I suspect we're done with the 100+ days.

Do you have an Exit profile configured to lower the seat to get out of the car? I do, and I set that profile only, to display the tire status. I get a quick glance at the tire pressures when I get out of the car. Tesla suggests not relying on the TPMS pressure for accuracy, but it is a nice quick check.