[Dog Face Pony Soldier]

I know the overwhelming consensus is the absolute correct tire pressure is listed in the door jamb, but I have always been skeptical. The prevailing method is that even if you change tire brand, model, even size; it is wrong to deviate from the door jambs pressure recommendation(s).

Over the last 26 years of driving, I have instead subscribed to the theory of using the recommended pressures in the door jamb as a guide only. Of course I would never exceed the maximum pressure listed on the tires sidewall, but I have instead used real-world performance as the final arbiter.

As an example, last week I took my 335i onto New Jersey Motorsports Park's Lightning track. Even though I removed the OEM RFT for Michelin PSS; I made sure to bring my cold tire pressure to BMWs recommended over 100 mph values of 39F/41R. After exploring this recommendation it was very clear this F/R balance needed to be adjusted to more front/less rear pressure. I am not exactly sure why a vehicle with more weight in the front would employ more pressure in the rear tires Maybe the pressures are calculated with the car loaded to max cargo capacity?

Now before everyone jumps in to argue (admittedly the overwhelming consensus position) that the jamb pressures shall not be deviated from regardless of the tire size/brand/type I feel my position is validated in the F30 Owners Manual.

If you look at the manual starting at page 186, you will see that our F30s actually have different pressures depending on the tires on the vehicle. Essentially this proves my point Different tires may/may not find the door jamb sticker to be the correct pressure.


Example: Standard recommended pressures for 335i sDrive/xDrive

225/45/18 (square): 32F/38R

225/45/18 + 255/40/18: 32F/35R


What about if you upsize to 19? Better adjust from that door jamb sticker!

225/40/19 + 255/35/19: 35F/38R


Same thing if you go all the way to 20

225/35/20 + 255/30/20: 38F/44R

[cwazy1]

on my 20's with 225/35/20 and 255/30/20 I run 40f/45r. I would never even consider running a 18 spec wheel's pressures in a 20. That would just be asking for trouble in seattle's shitty roads.

[Dippydo]

Originally Posted by cwazy1

on my 20's with 225/35/20 and 255/30/20 I run 40f/45r. I would never even consider running a 18 spec wheel's pressures in a 20. That would just be asking for trouble in seattle's shitty roads.

I was wondering what pressure to really run in my 20s. I was running 38 and seems to be a good fit so far.