Car Talk

January 1992

Dear Tom and Ray:
The owner's manual for my '89 Toyota Supra recommends 32 p.s.i. as optimal tire pressure in the original tires. I've since replaced the tires, and written right on the new tires, it says "maximum pressure 44 p.s.i." The funny thing is, they're the same size as the originals. Who's right, the car manufacturer or the tire sidewall? There's a big difference in ride between 32 p.s.i. and 44 p.s.i. Please give me an answer before I ruin my $800 rubber investment!
Chris

Beat up old car

TOM: Good question, Chris. This IS confusing, isn't it. And you're absolutely right--you COULD ruin your $800 rubber investment.

RAY: The trouble is that we often equate the words "maximum" and "best." You know, if your boss says "the maximum raise is 10%," then that's what you want. And in that case, you're right. "Maximum," at least for you, IS best.

TOM: But what if you've just been convicted of embezzling money from the company, and the law says the maximum sentence is 20 years? Now maximum isn't best anymore, at least for you (my brother has personal experience with this).

RAY: Yeah, I kind of thought minimum was best. But seriously, Chris, the answer to your question is right in your letter. You say that Toyota recommends 32 p.s.i. as "optimal." And when if comes to tire pressure, OPTIMAL is best. Maximum means maximum; i.e. if you put in more air than that, the tire could blow up!

TOM: Also, too much air wears out the tires in the middle. It also gives you poor handling, a very hard ride, and constant headaches from bouncing off the roof every time you hit a bump. Too little air gives you poor handling, too. But it also reduces gas mileage, and wears out the tires on the edges.

RAY: So you should always fill the tires to the pressure recommended by the vehicle manufacturer. In this case, Toyota's recommendation is optimal.

Back to the January 1992 index

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