I’ve never had tires this close to max psi

[Palmetto Fellow]

I’ve got 19” wheels on my E89. The door jamb suggests 44psi at the rear tires. The tires say max of 51psi.
In all the cars I’ve owned, the difference between suggested and max has never been this close. This is my first BMW and also my first car with 30-series profile tires in the rear.

Do you think 44psi cold puts me too close to max psi when warm, or is that a good number for these cars? Should I aim for 44psi warm? Or is there still plenty of safety built in at the max of 51psi?

What do you guys prefer?

Edit: I fully accept that I may be overthinking this

 

[Marcoose]

Pressure by itself doesn’t mean much.

With my suspension, engine, driving style, etc, I run 34 and 38 PS4S.

So it’s going to depend on what you have. What can you share ?

 

[Chippie]

Are the tyres run flats? If so then use the recommended pressure for the size/profile fitted, if the tyres are none run flats then most people tend to reduce the pressure to around 32/34 psi front and 34/36 psi rear

 

[Palmetto Fellow]

Pressure by itself doesn’t mean much.

With my suspension, engine, driving style, etc, I run 34 and 38 PS4S.

So it’s going to depend on what you have. What can you share ?

Stock car with Continental Extremecontact Sport tires, so they're not Run Flats anymore. The front tires are 2020 date stamped and rear are 2023. I will be replacing all 4 tires in the next year or two regardless of tread (which is still excellent). Those PS4S you've got are likely what I'll go with.
I've only put 300 miles on the car so far, and really do not want to put any money into it this year except for new oddments trays and MMI upgrade.

Are the tyres run flats? If so then use the recommended pressure for the size/profile fitted, if the tyres are none run flats then most people tend to reduce the pressure to around 32/34 psi front and 34/36 psi rear

It didn't even occur to me that the BMW recommendation would be specifically for Run-Flats. Thank you for this.

I'll be lowering my pressure to sub 40psi, probably close to what you guys are running.

I owned a 2014 Cadillac CTS in the past which had run flats on it, but I don't recall the door jamb recommendations from GM. It must not have been this close to max psi though as it never made me second guess anything.

 

[B21]

I’ve got 19” wheels on my E89. The door jamb suggests 44psi at the rear tires. The tires say max of 51psi.
In all the cars I’ve owned, the difference between suggested and max has never been this close. This is my first BMW and also my first car with 30-series profile tires in the rear.

Do you think 44psi cold puts me too close to max psi when warm, or is that a good number for these cars? Should I aim for 44psi warm? Or is there still plenty of safety built in at the max of 51psi?

What do you guys prefer?

Edit: I fully accept that I may be overthinking this

As Chippie said..these pressures only apply to these early designs of run flats made specifically for bmw…if you look at later Z4s that were fitted with MPSS and SC7s they use tyre pressures in the the range 28 psi to 38 psi..

The higher pressures are for cars running SUSTAINED speeds in excess of 100 mph..

 

[flybobbie]

How do you really know what pressure is actually in.
I have had various pumps with gauges and those tyre monitor jobbies. All read different.

 

[Fady]

Are the tyres run flats? If so then use the recommended pressure for the size/profile fitted, if the tyres are none run flats then most people tend to reduce the pressure to around 32/34 psi front and 34/36 psi rear

Guess people can set their tyre pressures to whatever they like for whatever reason they see fit, but would be happy to be pointed to some 'official' documentation which clearly indicates that pressures should be reduced for non run flats?

As discussed in a previous similar thread, the primary purpose of the air in the tyres is to support the load of the car and is not a factor of the actual tyre construction. I'm running PS4's and have stuck to pressures as indicated on the label on the door jamb. Plus - using the Vehicle and Model Guide as per the Michelin Website doesn't suggest that these should be deviated from.

 

[Chippie]

Guess people can set their tyre pressures to whatever they like for whatever reason they see fit, but would be happy to be pointed to some 'official' documentation which clearly indicates that pressures should be reduced for non run flats?

As discussed in a previous similar thread, the primary purpose of the air in the tyres is to support the load of the car and is not a factor of the actual tyre construction. I'm running PS4's and have stuck to pressures as indicated on the label on the door jamb. Plus - using the Vehicle and Model Guide as per the Michelin Website doesn't suggest that these should be deviated from.

As far as I am aware no E89 supplied by BMW were fitted with none fun flat tyres, so I doubt there will ever be any ”official “ tyre pressure recommendations from them, I suspect the higher run flats pressures are because of the much thicker side wall construction of the tyres, the MPS4S tyres I have fitted to mine have very thin side walls, and in my opinion inflating them to 44psi is like over inflating a cheep plastic foot ball, it will just bounce around, unlike a proper leather foot ball, which just hurts if you get hit in the face or the plumbs

 

[Marcoose]

Those PS4S you've got are likely what I'll go with.
I've only put 300 miles on the car so far

Being a new car to you, just drop 2-4 psi below recommendation, and see how it responds to your driving style. Then see if playing with 3-4 psi makes it better.

The E89 is heavy, and as stock has low grip and is lazy to turn. (At least the 35is is.) Very disappointing.

Good luck !