I took just enough physics to know that air (or whatever) doesn’t leak into tires, so after a particularly rocky ride down a spectacularly godawful stretch of alleged pavement — NE 36th from Kelley to Lincoln, if you’re curious — it didn’t occur to me to check the tire pressures.
And when I did, they were way the hell out of spec. Nissan calls for 33/30; the fronts were 35, left rear 34, right rear 32.
Now how did this happen? My best guess, and it’s not so great, is that the last time Gwendolyn got a spa day, someone thought the Dunlops had done flopped, and gave them an extra shot of air. This strikes me as slightly unlikely, since I’d carefully deleted the “rotate tires” bit from the to-do list, and they certainly didn’t rotate them. (The JWL mark is your friend.)
Anyway, after correction, the same stretch of road proved much less likely to bang my head into the sunroof, so I’m assuming that my gauge, despite its age (about five cars now), is still reasonably accurate.