Tires: correct tire pressue, tire placard, chevy suburban

Question
i have a 2005 chevy suburban 1500 z71 with p275/55/r20 tires need to know correct psi

Answer
Jim,

On every vehicle sold in the US, there is a sticker – commonly called the tire placard - that lists the original tire size and the proper pressure for that size.  The placard is usually located on a doorpost or in the glove box – but sometimes it is located in the trunk or on the fuel filler door.

BTW, it doesn't matter who makes the tire or what pressure is listed on the tire's sidewall, if the tire size is the same as the placard, then the pressure listed on placard is also appropriate.

One word of caution:  Some trucks use tires with the letters "LT" in front of the tire size - and some trucks use tires with the letter "P" in front of the tire size - and some trucks use tires with the letter "C" after the tire size.  You should not use "P"'s in place of "LT"'s and vice versa.

If you are using a tire size that is different than what is listed on the placard, then the pressure has to be recalculated.  The calculation is not difficult, but it requires tire load tables which are not allowed to be published in the Internet because of copyright laws.  However, I have a copy and would be glad to do the calculation, but the starting point is the vehicle placard: Tire size and inflation pressure.  I will also need to know the new tire size.

So we need to start with the vehicle placard - size and pressure.  I have a book - Tire Guides - that summarizes the vehicle placard of all cars sold in the US.  However, there are several versions of Suburbans, and they came with different tire sizes - and pressures.  So I need to know what the vehicle placard says before I can answer your question.