Quote:
Originally Posted by 08kermit
Right. The reason for "dry" nitrogen in racing tires is that the residual water in the atmospheric air can dramatically raise the pressure if it turns to steam. Optimal racing tire temp is above 200F. Street tires don't get nearly that hot, even cruising in the desert.
|
OK, I hate to get all technical here but someone may be bothered by this. The problem with racing tires is the temperature range and air will cause a greater pressure change than nitrogen. However, the water in the air in the tire is not liquid at normal operating temperatures.
We're conditioned to think that water boils at 212 F (100C) but that is at atmospheric pressure. When water vapor is in air it "boils" (vaporizes) when it reaches it's vaporization temperature at its "partial pressure". That's why water "boils" and "condenses" at normal atmospheric temperatures. To avoid confusion, we call that "rain" and "evaporation". The water itself is at a portion of the atmospheric (or tire) pressure and it will vaporize when it reaches it's boiling point at that partial pressure. Same concept as humidity and dew point.
In short, you may have a bit of water in your tires when you first start going on a cold morning but that will quickly heat up and evaporate.