Racing, moving to the next level Options

[Randal]

OK, all you big time racers out there, what is the correct procedure to purge air out of a tire before filling it with nitrogen?

The reason I ask is that any moisture mixed with nitrogen will create nitric acid, or some such vile stuff, if I remember correctly.

What about using air tools? Looks like a job for rubber gloves.

[Britain Smith]

Why purge?
Humidity inside your race tires causes the pressure to increase when heated. If the amount of humidity is decreased the tire pressure buildup is decreased. After each purge the humidity held in the air is replaced with a dry inert gas, such as nitrogen.


Why purge more than once?
Each successive cycle dilutes the remaining air until most, if not all, humidity laden air is replaced. A vacuum pump could be used but they are expensive, time consuming and you risk breaking the bead.

Why worry about pressure increase?
An increase in tire pressure changes the dynamics of the tire. The circumference of the tire may change and therefore change the stagger. The pressure change also changes the effective spring rate. If the pressure change can be minimized the tire will perform more consistently allowing the crew to concentrate on other areas of the cars’ performance.