Originally Posted by bbcutright
The tires are LT275/65R18 Toya's 550KPG 80PSI Cold
The yellow sticker says P265/65R18 S cold pressure says 220kPa, 32PSI Front and Rear
Spare P265/70R17 S 240 KPa, 35 PSI.
Not sure why I have a 17 inch spare? that's crazy.
17" tires and wheels are much less expensive than 18" hence 17" spare
RE the change from P to LT.
Did someone mislead you into believing that it is the tire that carries the load? The reality is that it is the air pressure that supports the load. To hold the 80 psi used in Load Range E tires you need a completely different tire construction and in all probability you need different wheels too as your OE 18" wheels are probably rated for no more than 50psi and maybe not even that much.
Simply changing tire type on a "passenger" light truck doesn't result in the TV becoming a real HD truck.
Fuel economy is strongly controlled by the mass of the rubber you are deflecting (bending) as you drive down the road. I bet your LT tires are 50% to 70% heavier than your P type tires. Your truck probably even had to meet fuel economy standards which is one reason you got P type tires OE. Trucks have a different set of standards and requirements.
I write a blog on RV tire application and safety. RVTireSafety.com
Also give seminars on tires at RV events across the US. 40 years experience as tire design & quality engineer for major tire mfg. Freelander 23QB on Chevy chassis is my RV