Tires: Pressure, proper inflation pressure, correct tire pressure

Question
Hi,
How do you know what the correct tire pressure is for you tires?  I do not have the manual for my cars, or the original tires.   

91 Tracker

Thanks.

Answer
Michelle,

Every light vehicle (passenger cars and light trucks) sold in the US has a vehicle certification label, common called the placard.  Among many things, the placard will tell you what the original tire size was and the proper inflation pressure for that size.  The placard is usually located on a doorpost or in the glove box.

I happen to have a booklet, called Tire Guide, that summarizes this and according to the book a 1991 Geo Tracker originally had a P195/75R15 for the 4X2 and a P205/75R15 for the 4X4, both types at 23 psi.

Personally, I think 26 psi is the minimum for P metric tires, just from the point of view of hold the bead onto the wheel.  Besides, I like to use 3 to 5 psi above the placard.  I get better fuel economy, better tire wear, better wet traction, better snow traction, better steering response, better tire durability, and only give up a bit of ride harshness.

"They" say you should check your tire pressures once a month.  Don't trust the guys at the shop to do it.  These guys are paid by the hour and this is one of the easiest things to shortcut.  Besides, there are a lot of mechanics you don't know where to look for the proper inflation.  No, it is not on the sidewall.

Buy yourself a tire gauge - a $5.00 pencil gauge works just fine, but I prefer the pistol grip digitals because they are remarkably accurate.  The check takes all of 5 minutes and it is the cheapest safety check you can make.  

Hope this helps.