Miata Mailing List: April 1993, Message #84
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   From: (none)
Subject: Tire Pressure
   Date: (none)

Well, it's been just over a month now since I picked up my '93.  I did the 
first oil change this weekend.  To my delight, I was able to unscrew the oil 
filter by hand and avoid getting the ``special'' wrench.

While I was in my grubbies, I decided to rotate the tires and check the 
pressure -- the first time I had since I got the car.  To my surprise, it was 
at 45 p.s.i. (cold)!  I quickly looked up what it was supposed to be (26), 
and corrected the situation, amazed that the dealer had over-inflated them so 
much.  Even the sidewall spec (stock Dunlop D89) says max pressure is 
35 p.s.i., and it hasn't warmed up *that* much since March.

Thinking that I should now road-test the car and see how this affected 
handling, I proceeded to the nearest twisty road and let 'er rip. The first 
effect I expected -- a much softer ride.  However, handling seemed to be much 
more sloppy.  On-center tracking was worse, and the feeling in general was 
kind of mushy.  I suspected that this was just my imagination (or the 
contrast from a rock-hard ride) until I entered a nice little tail-slide 
around a corner I'm very used to (full-throttle, second gear, ~5000rpm).  
Luckily, the miata is predictable.

Chagrined, I returned home and wondered what could be wrong.  Pressure 
gauge?  No -- it checked on-the-nose with a service station's.  I 
double-checked the door sticker to make sure it said 26 and I hadn't just 
read something else by mistake.

So, what's the deal?  Anyone else found a better pressure?  The tires even 
*look<8 low at 26 p.s.i.  For now, I've pumped them back up to ~32 'till I 
find out something better.

Thanks,

Russ Croman
Design Engineer
Crystal Semiconductor
Austin, TX