[carbo56]

On my 2018 M550 with 19" performance tires, the recommended pressures were 35 front and 38 rear. It had Michelin Pilot Sports run flats.

I picked up my 2021 M550, also 19" performance, and interestingly, the recommended pressures are 38 front and 35 rear. It has Goodyear Eagle F1 run flats.

At first, I thought that maybe it was a mistake, but it is listed that way in both the user manual and on the door frame. And the actual tires pressures were set exactly that way by the dealer.

BTW, the TPM system in the 2018 would show both the recommended (adjusted for temp) and actual pressures on the display, but the 2021 just shows the actual, and not the recommendation...

Any thoughts on why the flip/flop from 2018 to 2021? Seems strange...

[BimmerGeneral14]

Originally Posted by carbo56

On my 2018 M550 with 19" performance tires, the recommended pressures were 35 front and 38 rear. It had Michelin Pilot Sports run flats.

I picked up my 2021 M550, also 19" performance, and interestingly, the recommended pressures are 38 front and 35 rear. It has Goodyear Eagle F1 run flats.

At first, I thought that maybe it was a mistake, but it is listed that way in both the user manual and on the door frame. And the actual tires pressures were set exactly that way by the dealer.

BTW, the TPM system in the 2018 would show both the recommended (adjusted for temp) and actual pressures on the display, but the 2021 just shows the actual, and not the recommendation...

Any thoughts on why the flip/flop from 2018 to 2021? Seems strange...

Wow...that does seem very strange. I've never owned, or even heard of, any "normal" vehicle where the front TP was more than the rear. I'd love to know why. :

[LogicalApex]

Odd that it only shows the actual pressures and not the recommended. I'm very sure my MY2020 w/ iDrive 7 shows the recommended and actual pressures. Odd they would remove that. Perhaps a bug?

Originally Posted by BimmerGeneral14

Wow...that does seem very strange. I've never owned, or even heard of, any "normal" vehicle where the front TP was more than the rear. I'd love to know why. :

I agree. I wonder if this is down to a mistake on BMW part where they printed these backward and we'll see a revision on later cars to correct it.

[carbo56]

Even more strange is that in the owners manual, for the exact same 19" setup, it lists the 540i as 35/38 and the M550i as 38/35.

I am thinking that this has got to be a mistake. Who could be contacted at BMW able to provide a definitive answer?

[Raikkonen]

Assuming it's on your door jamb sticker, it would definitely be tested and then subsequently verified.

Although it is a flip from the previous iteration, I'm assuming engineers adjusted pressures this way to increase turn-in response (w/higher pressure), and better traction (lower pressure - rwd bias).

What a causal driver would actually recognize is another story, but if chassis engineers have determined that this is the optimal set-up for the new car, then I would definitely go with it!

[LogicalApex]

Originally Posted by Raikkonen

Assuming it's on your door jamb sticker, it would definitely be tested and then subsequently verified.

Although it is a flip from the previous iteration, I'm assuming engineers adjusted pressures this way to increase turn-in response (w/higher pressure), and better traction (lower pressure - rwd bias).

What a causal driver would actually recognize is another story, but if chassis engineers have determined that this is the optimal set-up for the new car, then I would definitely go with it!

But higher pressure on the front would increase traction and grip on the front in a RWD biased car. I am convinced it is a misprint by BMW that will get corrected via a recall and factory update.

[bimmer_335]

550 is front heavy as compared to 540... i'd think engineers have tweaked and settled on this.

[Raikkonen]

Originally Posted by LogicalApex

But higher pressure on the front would increase traction and grip on the front in a RWD biased car. I am convinced it is a misprint by BMW that will get corrected via a recall and factory update.

Yep, exactly what I said...

But...remember that grip and traction are different things...

Increase front tire pressure = Better turn-in (grip)

Lower rear tire pressure = Better traction

This is one on the simplest adjustments you can make at the track (or on the road in this case) in order to improve steering feel/feedback and improve acceleration by increasing the contact patch under load.

Spring rates also play a huge role in grip and traction.

I run higher front recommended pressure/lower rear recommended pressure on both my Boxster and 911 (991) to tremendous effect.

Load ratings also vary, depending on anticipated weight/max speed as well.

The only unusual aspect (for BMW at least) is that they're running higher overall front vs. rear....it's typically opposite for BMW, as they favor tire longevity by running lower front pressure (than rear) for most of their cars.

It may be an error, but I would highly doubt it, especially if the manual matches the door jamb.

[LogicalApex]

Originally Posted by Raikkonen

Yep, exactly what I said...

But...remember that grip and traction are different things...

Increase front tire pressure = Better turn-in (grip)

Lower rear tire pressure = Better traction

This is one on the simplest adjustments you can make at the track (or on the road in this case) in order to improve steering feel/feedback and improve acceleration by increasing the contact patch under load.

Spring rates also play a huge role in grip and traction.

I run higher front recommended pressure/lower rear recommended pressure on both my Boxster and 911 (991) to tremendous effect.

Load ratings also vary, depending on anticipated weight/max speed as well.

The only unusual aspect (for BMW at least) is that they're running higher overall front vs. rear....it's typically opposite for BMW, as they favor tire longevity by running lower front pressure (than rear) for most of their cars.

It may be an error, but I would highly doubt it, especially if the manual matches the door jamb.

I've given up on seeing the manual as a source of truth lately as they don't seem to be doing a good job reviewing them before printing.

My manual tells me to activate Valet Mode via iDrive and has said so since I took delivery (including the digital one). But that option doesn't exist in iDrive. Solution? BMW posted a TSB that if you come in complaining that you can't activate Valet Mode they'll put the switch there that they forgot to put there in the factory for the first 6 months or so of MY2020 production. MY2020 owners are super aware of how wrong our manuals are. Our printed and digital manuals are for the MY2021 LCI... And it is not hyperbole when I say that.

In this case tire pressures would be seen as a safety issue probably and they'll issue new stickers, but due to my experiences they'll let inaccurate data into the manual and etc.

[Raikkonen]

Originally Posted by LogicalApex

I've given up on seeing the manual as a source of truth lately as they don't seem to be doing a good job reviewing them before printing.

My manual tells me to activate Valet Mode via iDrive and has said so since I took delivery (including the digital one). But that option doesn't exist in iDrive. Solution? BMW posted a TSB that if you come in complaining that you can't activate Valet Mode they'll put the switch there that they forgot to put there in the factory for the first 6 months or so of MY2020 production. MY2020 owners are super aware of how wrong our manuals are. Our printed and digital manuals are for the MY2021 LCI... And it is not hyperbole when I say that.

In this case tire pressures would be seen as a safety issue probably and they'll issue new stickers, but due to my experiences they'll let inaccurate data into the manual and etc.

I hear ya...

My new X5 has been glitchy as hell, but always seems to resolve itself w/ a restart.

Anyhoo, if they do retract their printed (and electronic) tire pressure numbers, they'll have to issue a safety recall to replace stickers and reload software for the owners manual....what a waste!

Wouldn't surprise me either though...time will tell...

[carbo56]

To recap, the manual, the door jamb and also the TMS monitor on the display all say 38/35, which is the reverse of the 2018-2020 M550, and is also the reverse of the 2021 540. I called the BMW Genius hotline last week and asked them to check with engineering to verify if this was correct or a mistake. This is the response I got today:

Thanks for contacting the BMW Genius Team.

After speaking with our engineering contacts, they advised there could be various reasons why the tire pressure recommendation has changed. Some of these include a change in the curb weight, MY20 (4.372lbs) to MY21 (4,275lbs) which could have an impact on tire recommendations. Also customer feedback and/or changes to the driving characteristics of the car could dictate changes to tire pressures front-to-rear.

I hope this information is helpful. Thanks again for your inquiry.

I haven't had enough of a chance to sense if there is a difference in handling, and I am waiting until I hit 1000 miles to really let loose, so I will see what happens once I have a chance to really drive it hard.