Tire Air Pressure

[MBEEZ911]

This morning I went into Big-O-Tires (they use nitrogen w/free refill) in Tracy, Ca to get the air pressure checked for my tires. I went to America's Tire Co. first, but they don't use nitrogen and recommended I deflate my tires and put in regular air. When I purchased my tires from the dealership, they used nitrogen. My current tires are Michelin Pilot Sport Ribs Front: 225/40ZR18, Rear: 285/30ZR18 with nitrogen. I checked the owners manual for my 2002 911 Carrera Cabriolet and it recommended the front tire air pressure at 36psi and the rear at 44psi. My question is, is this the best setting for normal driving and does it matter whether I use nitrogen as oppossed to regular air?

[70Sixter]

Nitrogen is less likely to leak but unless you have two valve stems you'll never get pure nitrogen in the tire. Nitrogen is plentiful in the ambient atmosphere - about 78 percent.

So you don't have to evacuate the nitrogen to add air. Unless you suck out the air while feeding pure nitrogen.

Edit: And as far as pressures go the recommended values are good. For a little crisper turn-in I fudge the difference front to rear so they are at least a couple of lbs closer to each other.

Tracking the car is a good way to set pressure bias if you make incremental changes and note the effect.

Edited August 30, 2009 by 70Sixter

[goldenwarrior1]

Nitrogen is less likely to leak but unless you have to valve stems you'll never get pure nitrogen in the tire. Nitrogen is plentiful in the ambient atmosphere - about 78 percent.

So you don't have to evacuate the nitrogen to add air. Unless you suck out the air while feeding pure nitrogen.

Edit: And as far as pressures go the recommended values are good. For a little crisper turn-in I fudge the difference front to rear so they are at least a couple of lbs closer to each other.

Tracking the car is a good way to set pressure bias if you make incremental changes and note the effect.

See Consumer Reports article. The only substantial benefit I can see is if you are the guy selling it...

http://blogs.consumerreports.org/cars/2007...-nitrogen-.html