hamann69

What PSI should I run my stock tires at for daily driving?

Zod

follow what is written on your fuel cap it shows how much you need dependent on load and speed i think

NXtremeJeep

i run mine at 35psi

juicee63

42

Max.H

+1

chiromikey

+2

sick430

is that morning cold before any driving and also is that front and back. thanks

OzE55

F 36-38, R 38-40

hamann69

what psi would be for the smoothest drive.

sack5000

I run mine at 40 all the way around. A few PSI either way doesn't really matter and 40 is an easy number to remember.

dbarrym

Running a lower PSI will not help the ride much on 35 or 40 series tires, but will seriously (negatively) affect tire wear/lifetime. I've only had my 55 for a month but am using the factory settings - 38f/40r psi with just me in the car.

I used to run Pirelli P7's 285f/345r tires on my RSR and 930's, and lowering the psi below 38 or so would wear out the center of the tread prematurely.

MB_Forever

I set mine to 38 all around

amdeutsch

This does not compute; lowering would not wear our the center but the sides.

dbarrym

Sorry....but I can confirm from experience. Made no sense to me, either, but that was the explanation given to me by a Pirelli rep after replacing 2 sets of rear 35 profile 345's prematurely. He said that low pressure allowed the sidewalls to flex in at speed, and center of the tread thus would bow out, causing the center to wear faster.

Of course this was mid-80's tire technology, sidewalls are (I'm sure) much stiffer now.

jassim

I am using the factory settings - 36f/36r psi for my E63 .. but with Nitrogen not Air .... and some one told me that there is difference between Air psi and Nitrogen's psi .. !!

So, plz tell me what Nitrogen's psi that should be equal Air psi at 36f / 36r ??

MB_Forever

What's your feedback on Nitrogen? Is ride quality any better or worse?

Zod

My fuel cap does not say 40+ psi......why are some of you running this much?

MRAMG1

Guys, check the older threads as this has been heavily debated before. There is NO difference in ride quality or pressure with Nitrogen. A psi of air = A psi of nitrogen. The pressure functions as a spring rate for the tire, so if you need 40 PSI, you need 40 PSI, wether it be Nitrogen, Argon, Hydrogen, Air, etc, etc.

Nitrogen simply DOES NOT expand as quickly as air, so there is some SMALL benefit. It will make NO difference on the street, except to cost you more my friends.

See yeah

PS: Please don't try the Hydrogen, it was for comic releif only guys.

enzom

Curious - where did you get your factory settings from? I could swear that my door and the sticker behind the gas cap cover tell me to keep it at 35 all around with just me in the car.

dbarrym

These were suggested to me by my mechanic, knowing my driving style. I drive 10 miles of twisties to/from the office and 38/40 feels better to me than the suggested 35 psi. A touch more solid feel all-around, in particular the rear feels less 'soft' (loose) in trail braking and hard acceleration. I usually drive this section of road at 7 to 8/10th's (when I safely can - in the E55 the limits are pretty high!) and at 35psi cold the tires don't generate enough heat to get the pressures up to where the tire is working best.

35 psi is fine for daily use, you are correct re gas filler door sticker. To each his own.

Jon2007E63P30

+3

Nitrogen is simply not necessary for the street. The ONLY advantage I can see is that nitrogen fills have NO water.

If it was normal air at 21% oxygen and 78% nitrogen with no water vapor it would behave identically.

Water can change states and result in a larger tire pressure change with temp.


PV=nRT does not change much at all.
http://www.chalkbored.com/lessons/ch...aw-handout.pdf

Edit: Yea, I was right.
http://www.cartalk.com/content/colum...tember/05.html

mxyoung

Look to the B pillar - drivers side. The sticker tells you psi for both front and back. My stock Conti's - 41 in front and 46 in back.