Tires: Tire Pressure, Tire Pressure

Question
What is the optimum tire pressure I should use on my tires?  I have P275/55/20 Capitol TP9000 Negotiator tires on my 2006 Chevy crew cab short bed pickup and the tires do not list an operating PSI range.  The tire side walls list 50 PSI max load and not to exceed 40 PSI to seat bead when mounting and that's it.

Answer
Brian,

On every vehicle sold in the US, there is a sticker - commonly called the placard - that will list the original tire size and the proper pressure for that size.  On Chevy trucks, I think the placard is on the doorpost.

If you are using the same size as the placard, then the placard pressure is appropriate.

But if you are using a tire size that is different (and I can tell hat you are because of the 20" rim diameter), then the pressure needs to be recalaculated based off the placard.

Normally, I'd quote a book that lists the placard information, but there are so many variations of Chevy trucks that I can't tell what the placard might say.

So my starting point in this is the placard and I can't go any further without that information.  With that infoamtion, I am going to calculate the load carrying capacity of the original tires at the pressure specified, and then calculate what pressure is needed in the new tires to get the same load carrying capacity.

BTW, the reason the tire doesn't list an operating range is because the tire can't know what vehicle it is going on and it is the vehicle that determines what the tire size / pressure is supposed to be.