[Eucerin]

Car (iDrive 7) and mobile app says rear tire pressure should be 45. But the sticker next to driver's door says 42. Which one is correct?

[TurtleBoy]

iDrive/app takes into account the temperature of the tires so they both can be correct depending on the temperature. I think the decal is for 60 degrees.

[BobsM3Coupe]

Originally Posted by TurtleBoy

iDrive/app takes into account the temperature of the tires so they both can be correct depending on the temperature. I think the decal is for 60 degrees.

I always used 70° as the temperature for the decal air pressures.

[TurtleBoy]

Originally Posted by BobsM3Coupe

I always used 70° as the temperature for the decal air pressures.

You may be correct, I'm sure someone out there can confirm.

[Tejas1836]

<100 mph 42 psi; ≥100 mph, and/or full load, 45 psi

[streborx]

I think we're over-thinking this. Before TPMS, few drivers ever gave any thought to tire pressure and most did not own a pressure gauge, much less knew how to use one or even find a tire valve stem. Now that tire pressure is displayed on the iDrive screen, everyone is obsessed over a couple PSI. If 1 or 2 PSI was critical, warnings would flash all over the instrument cluster, and the ECU would shut down the car until tire pressure was corrected. Inflate your tires in accordance with the door panel sticker or tire manufacturer's spec, and call it aday. If you have an urge to stop on the freeway to release 2 PSI from one of your tires, I'll likely be the guy who runs you over.

[Guy Fleegman]

And does the door sticker know if you're swapped your original tires with something else that might have different requirements?

When it gets cold here I depend on the TPMS to let me know. My tire pressures have been 2-3 psi lower than the sticker since the day I drove it home. iDrive seems to okay with that.

[cellarrat]

Originally Posted by streborx

I think we're over-thinking this. Before TPMS, few drivers ever gave any thought to tire pressure and most did not own a pressure gauge, much less knew how to use one or even find a tire valve stem. Now that tire pressure is displayed on the iDrive screen, everyone is obsessed over a couple PSI. If 1 or 2 PSI was critical, warnings would flash all over the instrument cluster, and the ECU would shut down the car until tire pressure was corrected. Inflate your tires in accordance with the door panel sticker or tire manufacturer's spec, and call it aday. If you have an urge to stop on the freeway to release 2 PSI from one of your tires, I'll likely be the guy who runs you over.

In addition, neither the BMW-native system nor your AutoZone tire pressure gauge are what you could call precision instruments. The BMW app and the gauge built in to my compressor (set to the pressures recommended on te door jam) differ by 2-3 psi. I don't let it worry me. Much.

[Flying Ace]

It could be both. I would refer to the manual. There's an entire matrix of recommended tire pressures depending on tire compound type, anticipated speed, wheel size, and vehicle load

[jad03060]

Originally Posted by Flying Ace

It could be both. I would refer to the manual. There's an entire matrix of recommended tire pressures depending on tire compound type, anticipated speed, wheel size, and vehicle load

If you enter the proper tire type in iDrive, the computer will make a valid recommendation on what your ideal tire pressure is for them when at their current temperature. The pressure WILL change, even if there's no leaks as you drive them as they'll get warmer, raising the pressure, and as the weather changes.

The tire's pressure must drop a certain amount before the logic will trigger a low tire pressure alert. It's not uncommon this time of year to maybe get an alert when starting out with cold tires in the morning and have that alert go away as you drive when the pressure rises because of the tire warming. That is a signal you really should adjust the pressure for the current conditions as it affects wear, safety, and comfort.

[Guy Fleegman]

Originally Posted by jad03060

If you enter the proper tire type in iDrive, the computer will make a valid recommendation on what your ideal tire pressure is for them when at their current temperature. The pressure WILL change, even if there's no leaks as you drive them as they'll get warmer, raising the pressure, and as the weather changes.

The tire's pressure must drop a certain amount before the logic will trigger a low tire pressure alert. It's not uncommon this time of year to maybe get an alert when starting out with cold tires in the morning and have that alert go away as you drive when the pressure rises because of the tire warming. That is a signal you really should adjust the pressure for the current conditions as it affects wear, safety, and comfort.

Score another hit for the forum. It had not occurred to me to check iDrive for the tire setting. Turns out it was programmed for "Summer" as in 20 or 21" performance. The other option was Winter/All Year, with 19" all season, which is what I have.

Why the factory setting was incorrect I don't know but I appreciate the heads up.

[Bavar-ian]

There's also a setting for partially loaded eco or fully loaded.
That changes the recommended psi in idrive.
Im on 45 all round.

[cellarrat]

Originally Posted by jad03060

If you enter the proper tire type in iDrive, the computer will make a valid recommendation on what your ideal tire pressure is for them when at their current temperature. The pressure WILL change, even if there's no leaks as you drive them as they'll get warmer, raising the pressure, and as the weather changes.

The tire's pressure must drop a certain amount before the logic will trigger a low tire pressure alert. It's not uncommon this time of year to maybe get an alert when starting out with cold tires in the morning and have that alert go away as you drive when the pressure rises because of the tire warming. That is a signal you really should adjust the pressure for the current conditions as it affects wear, safety, and comfort.

I hadn't even thought to check. Thanks; I'll do that this afternoon!

[BillD1953]

509 miles since new.
cold tire inflation in NH 60F ish temps
38F
42R
19's