OK May be a DUMB question but thought I would ask anyway. I have P235-75-15 on my truck right now. Now what I want to know what the difference is between the P rated tires and the LT rated tires. I had to have a tire replaced(Got a fair size hole in the sidewall, couldn't be fixed) Now when I put the two side by side the LT's looked a little bigger. Isn't it just the strength of the side wall right?

 

Mostly correct.
Teh P stands for passenger tire, and yes it has a weaker side wall due ot less cords.
The LT stands for Lgith Truck and it has stronger side walls for carring heavier loads, like a trailer, or wights int eh back end.

Typically LT tires will also have deeper treads then P tires. Truck tires are typically constructed to handle more rugged terrain then P rated tires. So it is entirely possible that your LT tires are phyically bigger then the P rated tires, although it shouldn't be more then like a 1/4" or so.

Part of the reason tehy may look bigger is due to the tread pattern. On the Lt tires the tread goes all the way to the edge and usually is blocked off, while the P tires are rounder on the edge.

 

Yeah, what he said!