[jcardea]

Good day to all, I have question of tire pressures versus tire monitoring system. I decided to check actual tire pressures on my new X5 this weekend. I wanted to make sure my tire gage matched readout on the monitoring graphic screen. It did match correctly to reading on screen. I then looked at tire pressure label in the inside door jam and it says 35PSI for front and 42PSI for rear. First of all, I have never seen two different pressure recommendation for the same type tire between front and rear. But this is my first SUV, I have only had sedans all of my life. But what was actually in each tire was over 50PSI. so, I reduced pressures in all tires to meet the label in door. Thus 35 in front and 42 in rear. I should state these are all cold pressure measurements, car sat all night. Next, I got inside car and started it up and it immediately gave me a notification warning of low tire pressure. In looking at graphic each tire illustration was still green in color and each showed exactly what tire label called for. It would not let me clear this notification. Since most tire sensors “go to sleep mode” if not moved for a long period of time, I thought that they needed to just need to wake up, so I drove car for several mile to warm up tires. But notification never changed even as each tire pressure raised as they warmed up. So, I let thing go back to a cold state and added about 2PSI to each tire to 37 front and 44 rear. Still same thing. I have the 21-inch Pirelli run flat ties and on their side wall states what the load rating is with a 50PSI MAX on them. What is going on with this??? First of all, each tire came from factory over inflated which is not unusual, but why am I getting low tire pressure warning if I put them at recommend pressure based on door label??? Do I need to make all tire equal again at say about 48PSI or so???

[nZtiZia]

after you lowered the tire pressures according to the B pillar panel, what you forgot to do was reset the TPMS in iDrive to the new baseline values of 35/42. it still thought the tires are supposed to be 50. so when the tires have cooled down, ensure they're at 35/42, then go into the TPMS screen and perform a reset. You will have to drive for several minutes while it calibrates to the new baseline pressures. I believe it will reach full calibration more quickly if you drive on roads with turns instead of a straight line.

[Auricom]

More information about tire pressure, TPMS, target pressures in iDrive Tire Settings:

https://g05.bimmerpost.com/forums/sh....php?t=1807345

But TL;DR:
Reference the driver's door pillar label for tire pressures for optimum driving comfort and up to 100mph / 160kmph

Adjust tire pressures then drive around until tire pressure baseline calibration is complete.

[jad03060]

The tire pressure may not have been adjusted properly during the predelivery checks the dealer is SUPPOSED to do. During that check/setup, he's supposed to check and then reset the TPMS so that it recognizes the 'normal' pressure.

Note, the readout on the iDrive (at least as I've got mine configured) shows two separate numbers for each tire...one is the actual pressure, and the second is based on the current tire temperature, what the ideal is. Tire pressure will change with both the temperature (about 1#/10-degrees F) and altitude changes, and, say the sun is hitting one side of the vehicle, those tires could easily be warmer, and thus, a higher temperature may be expected. The computer adjusts what the ideal pressure is based on the actual conditions. If you go drive the vehicle and the tires are warm or hot, and you decide you want to adjust them, use the suggested pressure, not the one on the door post. Once they cool back off, they should approach that nominal pressure.

When you reset the TPMS, it does two things:
- locates where each tire is
- sets the current pressure as the normal pressure

After the reset, it looks for changes...if they're big enough and not explained by the temperatures, it will alert you when they're low (but not high, as far as I can tell). So, resetting them is setting your new 'normal' condition based on what it sees after successfully resetting.

[TurtleBoy]

Originally Posted by nZtiZia

after you lowered the tire pressures according to the B pillar panel, what you forgot to do was reset the TPMS in iDrive to the new baseline values of 35/42. it still thought the tires are supposed to be 50. so when the tires have cooled down, ensure they're at 35/42, then go into the TPMS screen and perform a reset. You will have to drive for several minutes while it calibrates to the new baseline pressures. I believe it will reach full calibration more quickly if you drive on roads with turns instead of a straight line.

There should be no need to reset the TPMS in this situation. Just drive and they will adjust.

More than likely the tires were/are not set to the correct size/type if the notifications continue.

[nZtiZia]

Originally Posted by TurtleBoy

There should be no need to reset the TPMS in this situation. Just drive and they will adjust.

More than likely the tires were/are not set to the correct size/type if the notifications continue.

the OP did just that and it gave him a low pressure warning. a reset has to be done to set the new baseline pressures in TPMS. Otherwise, how would it know to warn you if it doesn't know if the current pressures are dangerously lower than the baseline pressures to begin with? After the baseline pressures are set, then I agree with you that subsequent top ups don't require a reset, but the system needs to start somewhere, and they were set too high from the factory (whether on pressures alone or incorrect size/type). I wouldn't put it past the factory to set the incorrect tire size or type. it happened on mine and others here.

here's how i know baseline tire pressures need to be reset:
in Dec '20, i took delivery of my 45e, which came with 21" summer tires. upon learning my new car, i noticed TPMS had winter/all year selected, so i changed to summer. my B-pillar tire panel said 38/44 and existing pressures were fine. a month later, i decided to switch to 20" all-around with AS tires, so i went into TPMS, entered the new 20" tire size as well as winter/all year, and do you know what the recommended tire pressures were after i finished driving? 38/44! why? because that's what the tire installer inflated them to cuz he went by the B-pillar 21" tire pressures. in other words, TPMS still recommended 38/44 even though i changed the tire size from 21" to 20" because those were the pressures inside my tires.

i had a gut feeling that wasn't correct, so i reached out here in the forum and got mixed answers for the correct 20" tire pressures. some went off the panel, some personal preference. i wanted to know what the factory says they should be, so i started a new thread specific to finding correct pressures for a 20" square setup in the US 45e and found one person who also had a US 45e. he shared his B-pillar panel which showed 35/42. so i deflated my tires to match and about a week later, i got a TPMS low pressure warning in the two rear tires, which read 37 (likely dropped due to the winter weather). i was confused: 37psi shouldn't have set off the TPMS warning being only down by 5psi, but it was at that point i realized it sent a warning because 37psi is actually 7psi lower than what the baseline of 44psi was set to previously.

after an overnight wait in my enclosed garage, i adjusted my tire pressures to 35/42, went into TPMS, and while there no longer exists a RESET option, i selected my same 20" tire size and drove off. it then calibrated and now my recommended pressures always show 35/42 (cold pressures). it is from this point forward (after establishing the new baseline pressures) i should never have to "reset" TPMS after topping up.

[TurtleBoy]

Originally Posted by nZtiZia

the OP did just that and it gave him a low pressure warning. a reset has to be done to set the new baseline pressures in TPMS. Otherwise, how would it know to warn you if it doesn't know if the current pressures are dangerously lower than the baseline pressures to begin with? After the baseline pressures are set, then I agree with you that subsequent top ups don't require a reset, but the system needs to start somewhere, and they were set too high from the factory (whether on pressures alone or incorrect size/type). I wouldn't put it past the factory to set the incorrect tire size or type. it happened on mine and others here.

You are correct:

[jcardea]

Originally Posted by TurtleBoy

There should be no need to reset the TPMS in this situation. Just drive and they will adjust.

More than likely the tires were/are not set to the correct size/type if the notifications continue.

you are correct, I had driven around for many miles and nothing had changed. So after reading replies yesterday and it turns out that the tire selection was set to "Other". So I selected my correct tire size and it set itself then on my way home form work after few mile it recalibrated and all is well now
Thanks to all

[nZtiZia]

Originally Posted by jcardea

you are correct, I had driven around for many miles and nothing had changed. So after reading replies yesterday and it turns out that the tire selection was set to "Other". So I selected my correct tire size and it set itself then on my way home form work after few mile it recalibrated and all is well now
Thanks to all

checking to make sure the tire size/type is correct in TPMS shouldn't be part of a new owner's "getting started" checklist, but maybe they set them that way before transport via train, truck or ship, so knowing this will be useful with future bimmers.

as long as your tire pressures were set according to the B pillar panel before you set the correct type/size in TPMS and drove off, then iDrive will reflect the correct reference values.