Confirm PS4S pressure

[gerri]

I mounted 4 Michelin PS4S 255/19-275/19 on my F83 and put pressure to BMW specification for 2 people only at 2.6 bars (38 psi) front and rear. Yesterday I had the opportunity to test the speed of the car but at 255 Km/h (158 mph) the front seemed "light" to me, it seemed that the car was unstable and I left the attempt to reach 280 (174 mph). I searched on the Michelin site and it says that for F83 there must be 2.2 bars (32 psi) front and 2.3 (33,3 psi) rear. Could the difference in pressure cause this sensation? F83 owners with PS4S what pressure they use. Thank you!

[Kilabyte]

Do you have any suspension work or coding done?

I run all 4 at 33psi.

When was the last time you had the car aligned as this will be a bigger issue.

[gerri]

Originally Posted by Kilabyte

Do you have any suspension work or coding done?

I run all 4 at 33psi.

When was the last time you had the car aligned as this will be a bigger issue.

The suspensions are factory and I have no codes

But yours is not a convertible, different weights ...

I did the alignment after fitting the new tires

[alex2364]

The owners manual have separate tire pressure recommendations for speeds higher than 100 mph.

[Fat Goose]

Originally Posted by gerri

I mounted 4 Michelin PS4S 255/19-275/19 on my F83 and put pressure to BMW specification for 2 people only at 2.6 bars (38 psi) front and rear. Yesterday I had the opportunity to test the speed of the car but at 255 Km/h (158 mph) the front seemed "light" to me, it seemed that the car was unstable and I left the attempt to reach 280 (174 mph). I searched on the Michelin site and it says that for F83 there must be 2.2 bars (32 psi) front and 2.3 (33,3 psi) rear. Could the difference in pressure cause this sensation? F83 owners with PS4S what pressure they use. Thank you!

I have an F83 as well and felt the same “lightness” at speed. Installed the “lightweight” front lip and it planted the front end at speed and fixed the “light” feeling. End up installing a CS style rear spoiler to balance the aerodynamics.

[ONEof500]

Originally Posted by Fat Goose

I have an F83 as well and felt the same “lightness” at speed. Installed the “lightweight” front lip and it planted the front end at speed and fixed the “light” feeling. End up installing a CS style rear spoiler to balance the aerodynamics.

This

[gerri]

Originally Posted by Fat Goose

I have an F83 as well and felt the same “lightness” at speed. Installed the “lightweight” front lip and it planted the front end at speed and fixed the “light” feeling. End up installing a CS style rear spoiler to balance the aerodynamics.

What pressure do you have on the tires?
Do you have a photo of the front?

[gerri]

Originally Posted by alex2364

The owners manual have separate tire pressure recommendations for speeds higher than 100 mph.

In my use and maintenance manual in the wheels and tires section there is no mention of inflation pressures. I have read it carefully. If you can / want to put a photo of your manual page that talks about it, you would do me a great courtesy.

[EezyBeezy]

Over in the Michelin PS4S thread I read 32psi all around is recommended.

[alex2364]

Originally Posted by gerri

In my use and maintenance manual in the wheels and tires section there is no mention of inflation pressures. I have read it carefully. If you can / want to put a photo of your manual page that talks about it, you would do me a great courtesy.

This is for the F82. I don’t know if the F83 is different.

[gerri]

Originally Posted by EezyBeezy

Over in the Michelin PS4S thread I read 32psi all around is recommended.

I have also read discussions on the PS4S and the majority has 32/33 psi which is also the pressure recommended by the Michelin site and I don't understand why in Europe BMW recommends 37 to 45 bar depending on the load.

[krudmunk]

Originally Posted by gerri

I have also read discussions on the PS4S and the majority has 32/33 psi which is also the pressure recommended by the Michelin site and I don't understand why in Europe BMW recommends 37 to 45 bar depending on the load.

I think 32/33 psi is recommended by manufacturer for proper wear and tear and to achieve the estimated life range of the tires.

It is highly recommended to increase to 36/37 psi if you reach higher speeds. But also, at the same time, you lose some life range of the tires. Meaning the higher psi will wear your tires faster

[dizz81]

Just got new tires put on my car this weekend at the BMW dealership. I checked the pressure for the tires and they're all 33. I would guess the dealership knows what the pressures should be and if they put them at 33 then that would be where they should be at.

[Fat Goose]

Originally Posted by gerri

What pressure do you have on the tires?
Do you have a photo of the front?

Originally Posted by gerri

What pressure do you have on the tires?
Do you have a photo of the front?

Best photo I have of the front for now. Lightweight front lip is the only front aero piece and it "planted" the front end at speed (~165 mph).

Like everyone has said, 33 PSI or 2.275 Bar all around COLD.
I check them right in the morning before the sun has time to heat them up.

Now for 100+ mph ops just make sure the car and tires are warmed up (drive around for 20 mins or so) before testing the "limits."

[N44RP]

Grab some more photos, I’ve got the same lip waiting to be mounted and would like to see it on the convertible

[Fat Goose]

Originally Posted by N44RP

Grab some more photos, I’ve got the same lip waiting to be mounted and would like to see it on the convertible

Attached!

[N44RP]

Woohoo thank you brother!

[PAPA PA]

While recommended tire pressures are generally on the door placard on the drivers side, my recent experience on the PSAS4s and PSSS on both my AMG and Audi suggest 34-35 is ideal. On these heavier vehicles, slightly more pressure gives an enhanced turn in and mildly improved mileage, with limited loss in traction or tread life.

Best of luck!

[Innovade]

I run 33 PSI on all 4. I'm using PS4S

[MineralWhiteF80]

i think you will find that the tire pressure is not the cause of the "light" and floaty feeling at high speeds. It is more the soft factory suspension coupled with the ride height allowing air to get under the car. Everything is exaggerated at high speeds. Small bumps become large bumps, light winds become noticeable winds, etc.

When I have my coilovers set on comfy street mode, my car gets light and floaty at higher speeds (130+ mph), but when I stiffen them up to track setting, the car feels planted without issues and that is with the same tire pressures.

For my PS4S, I set my pressures when cold to 35 psi (2.4 bar) on the street and 29 psi (2 bar) on the track.

Here is a fun picture I took a screenshot of out of one my track day videos showing the pressure increase and temperature increase of the Michelin PS4S tires after a 20 minute HPDE track session. At the start of the session, the tire pressure was 29 psi and 85 degree tire temps!

[Edit] Just wanted to add that higher tire pressures set for going high speeds is not a matter of getting rid of the floating light feeling. It is to reduce sidewall flex. Tires with higher pressure generates less heat from tire flex and prevent tire failure better than the same tire at lower pressures.