CORRECT TIRE PRESSURE!
01-31-2007, 07:28 PM
#17
Rennlist Member
Namvet, if that's hot pressure, that's pretty close to what I run. I set them at 30F/28R COLD and get nice even wear and great traction -- no rolling under of the sidewalls either. It depends on what tire/rim, etc, YMMV.
01-31-2007, 07:51 PM
#18
Fleet of Foot
Rennlist Member
Rennlist Member
H, I seriously doubt that Porsche just threw those #'s out there without any kind of research/testing. My feeling is that the higher rear pressure has to do with rear tire sidewall stiffness/deflection when the car is driven aggressively. Most American manufacturers designate pressures for ride comfort (Ford Explorer 
) with secondary consideration given to handling concerns.
Anyone that is a newby at an autox and running on street tires is given the advice to increase tire pressures in the interest of sidewall stiffness, mark the tires with chalk or white shoe polish, observe what if any sidewall rollover occurs and adjust pressures appropriately.
That being said, I'm with Dr. Bob here with the rears at @ 40 psi as at 44 I do get noticeable wear in the center of the tread. Anything lower than 40 in the rear feels "mushy" to me, a feeling I don't care much for. 36 up front seem just right to me, but that may have more to do with the way I drive
, not to mention Porsche has been doing this a few days. I would tend to believe they know what they're talking about.
) with secondary consideration given to handling concerns.Anyone that is a newby at an autox and running on street tires is given the advice to increase tire pressures in the interest of sidewall stiffness, mark the tires with chalk or white shoe polish, observe what if any sidewall rollover occurs and adjust pressures appropriately.
That being said, I'm with Dr. Bob here with the rears at @ 40 psi as at 44 I do get noticeable wear in the center of the tread. Anything lower than 40 in the rear feels "mushy" to me, a feeling I don't care much for. 36 up front seem just right to me, but that may have more to do with the way I drive
, not to mention Porsche has been doing this a few days. I would tend to believe they know what they're talking about.
01-31-2007, 08:12 PM
#19
Three Wheelin'
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Higher pressure have to do with tire drag. Softer pressure allow for more grip when launching as there is more surface area in contact with the ground. Once moving you want less surface area in contact. You want just enough to not slip, but no more. Low pressure tires on the Autobahn at high speed are like trying to roll a half full water balloon. Now take the water balloon and fill it completely full. rolls much easier and truer. Less vibration as well as the tire stay more concentric. Another way to look at it is wearing snow shoes. They are great for grip in the snow and slow moving. But try running in them...
So bottom line is high speeds require the higher pressure for lack of surface drag and a more stabile concentric tire shape. That's why higher pressures give you better gas milage as well. The fronts are kept lower as a compromise to allow a larger patch when turning at high speed.
So bottom line is high speeds require the higher pressure for lack of surface drag and a more stabile concentric tire shape. That's why higher pressures give you better gas milage as well. The fronts are kept lower as a compromise to allow a larger patch when turning at high speed.
