[thatBimmerBloke]

I keep reading mixed suggestions on this. I switched from OEM 245/45 R18 run-flats to 255/40 MPSS (non-run-flats). My car shows I need 32 front and 34 PSI for the rear tires but shouldn't it be different now that I have deviated from OEM spec tires?
Currently running 32 PSI feels a bit mushy and they kinda look under-inflated, maybe it's just the bulge due to 8.5" wide wheels? I've been reading people suggesting 34/36 to 36/38 PSI, some even have it at 40PSI.
Any suggestions?

[Gen13 F36]

Is front and rear different on a square setup? I never run different setup on my old civic si.
Is it the same here ...maybe 36 all around.


I have staggered setup on my F36.... first time I had my non RFT... I set it at 36F / 38R. Drove it for a 2 weeks and decided it was too hard. I then adjusted them to oem (door) 32/34. Too soft. I end up around 34 F and 36 R sweet spot for my non RFT indy 500

[ntailor]

I'm running 35 all around on a 255/40/18 set up. Initially the tire shop did 32 all around and it felt soft. I bumped it up to 35. So far it feels better but due to covid, haven't driven it much. Just got the tires the weekend before this started.

[MacklinUSOB]

I run mine a cold 32 front and 35 rear with a 245 square setup. The reason for the stagger in pressure is because tires build and maintain heat differently on each axle. Once the car is warmed up the pressures and temperatures stay at or near equal to maintain handling balance. If you are going to step up or down the pressure from the recommended specification, step it up or down the same amount all around. When making any tweaks pay attention to the TPMS readouts and see how the temperatures/pressures balance, if they don't balance out take note and most importantly -- only alter pressures when completely cold.

Run flat tires have stiffer sidewalls but sidewall stiffness should never supplement pressure, this goes for all tire constructions. Air pressure is what supports the weight of the vehicle under normal operation. Also note that while there is a recommended stagger on our vehicles there are others (like the M2) that say don't. There is a huge amount of math and practical testing behind these pressure specifications because every chassis is going to be different. On a stock car driving on the street the placard is ideally where you want to be. If you start changing the car or the way you drive it (track day) then the cold pressures will likely need adjustment. The goal is to maintain uniform pressure and temperature on all corners to keep the tires within their peak performance envelope regardless of the use case.

[thejeremyman9]

Originally Posted by Gen13 F36

Is front and rear different on a square setup? I never run different setup on my old civic si.
Is it the same here ...maybe 36 all around.


I have staggered setup on my F36.... first time I had my non RFT... I set it at 36F / 38R. Drove it for a 2 weeks and decided it was too hard. I then adjusted them to oem (door) 32/34. Too soft. I end up around 34 F and 36 R sweet spot for my non RFT indy 500

I am similar at 35F 38R with MPSS 245/35/19 and 255/35/19. This is actually the OEM door placard spec for stock staggered 19s on a 335i Msport. I actually thought the tires "looked" too low with this pressure (after switching to non RFT) but the ride and performance seems good.

[thatBimmerBloke]

Thanks guys, I had filled it up at 32psi but my TPMS was showing 29 and I refilled it to 34F and 37R. The car feels much lighter now, it was feeling kinda heavy and harder to steer around, was definitely running low. Also, the tires don't look under-inflated now.
I think the M-Sport cars with 19" non-run-flats also have something like 35F and 38R printed by the door.

Gen13 F36 I've 255/40 R18 square setup.

[BMWILUVU]

These are benchmark pressures. You should adjust these pressures slightly to suit your ride and look at treadwear to see where the wear is.