SR-71 Facts: 29 Details That Might Surprise You
Tires Filled With 415 lbs./sq. inch of Nitrogen
At the speeds the SR-71 flew, the tires heated up just like the airframe even though they were housed inside of a cell. If normal air was used to inflate the tires, the oxygen would seep out even while the landing gear was retracted. To combat that issue, pure nitrogen became the standard to inflate the 415 lbs./sq. inch tires. Also, these tires were 2-ply. A typical commercial airliner only inflates its tires to about 200 pounds per square inch.