Tires: tire pressure, inflation pressure, load index

Question
I own a '99 cougar with Kumo low pro tires. The pressure on the tire says 51 psi. I was wondering the pressure to use.

Thanks
Andrew Elbert

Answer
Andrew,

The first step is to find the vehicle placard.  It will have the original tire size and inflation pressure.  Placards are usually located on a doorpost or in the glove.

If you are using the same tire size as listed on the placard, then the inflation pressure listed there is appropriate.

However, if you are using a different size than is listed there, the pressure has to be recalculated.  It's a simple calculation, but it requires the use of tire load / inflation tables, which are only published in a yearly reprinted book - which I happen to have.

So if you would like me to recalculate the pressure, I need the tire size and pressure listed on the placard and the new tire size on the vehicle.  Please include the letters in front of the size if they are there and the load index that is listed after the size, if that is there as well.