[mjshaw63]

iDrive recommended tire pressure values assume maximum rated payload capacity. If I follow the recommended settings (F-35psi, R-42psi) and drive empty (single driver no cargo) most of the time, my tires (especially the rear ones) will begin to show over inflation wear, i.e. wear in the center of the tread.

Knowing that my G20 has an almost 50/50 weight distribution in this configuration, I have determined through careful analysis, including consulting Bridgestone's tire pressure tables, that my G20 with Bridgestone 225/40R19s RFs at all four corners wear uniformly if they are all maintained at 35psi (with no handling impacts and marginally better ride quality). Unfortunately, the iDrive doesn't like this setup.

Is there a way to change the iDrive recommended tire pressure settings so that I can run 35psi at all four corners and keep iDrive happy?

[HighlandPete]

Originally Posted by mjshaw63

iDrive recommended tire pressure values assume maximum rated payload capacity. If I follow the recommended settings (F-35psi, R-42psi) and drive empty (single driver no cargo) most of the time, my tires (especially the rear ones) will begin to show over inflation wear, i.e. wear in the center of the tread.

Knowing that my G20 has an almost 50/50 weight distribution in this configuration, I have determined through careful analysis, including consulting Bridgestone's tire pressure tables, that my G20 with Bridgestone 225/40R19s RFs at all four corners wear uniformly if they are all maintained at 35psi (with no handling impacts and marginally better ride quality). Unfortunately, the iDrive doesn't like this setup.

Is there a way to change the iDrive recommended tire pressure settings so that I can run 35psi at all four corners and keep iDrive happy?

It is not just weight distribution, geometry also plays a part in recommended pressures. If you are on M-sport suspension calibrations, be careful of a low rear pressure, (particularly with run-flats), easy to knock off the inside shoulders well before you worry about mid wear.

Also remember the suggested pressure in iDrive is the temperature related, running/working pressure, not a cold setting pressure.

[jg4c]

Originally Posted by HighlandPete

It is not just weight distribution, geometry also plays a part in recommended pressures. If you are on M-sport suspension calibrations, be careful of a low rear pressure, (particularly with run-flats), easy to knock off the inside shoulders well before you worry about mid wear.

Also remember the suggested pressure in iDrive is the temperature related, running/working pressure, not a cold setting pressure.

This topic always brings me back to the same question.

As I always set my tire pressure to the door jamb numbers cold,
why would I need to be concerned about what drive says I should
follow for running/ working pressure?

Unless after some time driving, and a tire lost pressure for some reason,
and needed to fill with air, I could see what Idrive says to use.

[HighlandPete]

Originally Posted by jg4c

This topic always brings me back to the same question.

As I always set my tire pressure to the door jamb numbers cold,
why would I need to be concerned about what drive says I should
follow for running/ working pressure?

BMW's explanation...

Unlike the tire pressure sticker, the electronic tire pressure label permanently monitors the nominal pressures taking into consideration the current temperatures. This means that it determines and displays the optimum tire pressure at any temperature.

Optimum adjustment of tire pressure is necessary for the following reasons:
• Best possible driving dynamics.
• Maximum utilization of tire service life.
• Reduction of the fuel consumption.
• Optimum operation of various suspension control systems.

Makes sense, as cold setting pressures are only 'approximate' for the range of use, speed, load, etc.

I know from my own experience that the recommended cold setting pressure isn't always appropriate for all ambient temperatures and trip duration. May need some adjustment to run at the optimum pressure for performance and wear.

[mjshaw63]

Highland Pete, thanks for the response. When you say that when running low rear pressures it is "easy to knock off the inside shoulders", do you mean under-inflation wear, or something else? I am keeping a careful eye on the wear patterns of the rears after having reduced them to 35psi. And yes, they are run flats.

[HighlandPete]

Originally Posted by mjshaw63

Highland Pete, thanks for the response. When you say that when running low rear pressures it is "easy to knock off the inside shoulders", do you mean under-inflation wear, or something else? I am keeping a careful eye on the wear patterns of the rears after having reduced them to 35psi. And yes, they are run flats.

With a normal tire, there is more flexibility in the sidewall, this helps cope with a bit of camber, before we would see the signs of under-inflation. Run-flats with the stiffer sidewalls will therefore load one sidewall with camber, well before the typical under-inflation of the normal tire. We really have to be on the crown of the run-flat tire to prevent the premature wear due to more camber sensitivity.

This wear is affected by both static camber settings and dynamically, when driving lots of sharper bends and faster turns.

Many users have learned the hard way, being caught out with rapid inner shoulder wear, due to being on the lower side of optimum.

See how local and extreme it can be.

[JABCAT]

I think the BMW I-drive recommendations are unnecessary. I set my pressures to the cold pressure listed on the door jamb sticker in all my vehicles and have no issues with abnormal tire wear. My 330e has uniform wear front & rear at 20k mi. I drive solo in my vehicle 99% of the time. I think I've looked at the I-drive once & paid no attention to it.

[HighlandPete]

Originally Posted by JABCAT

I think the BMW I-drive recommendations are unnecessary. I set my pressures to the cold pressure listed on the door jamb sticker in all my vehicles and have no issues with abnormal tire wear. My 330e has uniform wear front & rear at 20k mi. I drive solo in my vehicle 99% of the time. I think I've looked at the I-drive once & paid no attention to it.

Keep in mind, many users do not check tire pressures regularly, some not at all. One of the key reasons for having legislation regarding TPMS.

Even with door plate/sticker recommendations, it surprises me how many topics we have on this forum, asking "what tire pressure should I use?"

[JABCAT]

Originally Posted by HighlandPete

Keep in mind, many users do not check tire pressures regularly, some not at all. One of the key reasons for having legislation regarding TPMS.

Even with door plate/sticker recommendations, it surprises me how many topics we have on this forum, asking "what tire pressure should I use?"

If they're not checking tire pressures regularly, then I doubt they're scrolling through the idrive and looking at the dynamic pressure recommendations. I agree with you re: not looking at the door jamb sticker. One would think manufacturers stopped providing owner's manuals with as many basic questions that are posted on every car forum. Questions that can clearly be answered by reading one's manual.