Looking at purchasing new tires for my 04 LS - Here's my question, since 245-70-16 is standard, how much will a 245-75-16 affect the truck and will they work? As anyone used this size yet on their TB?

Thanks

Slightly taller and narrower.

Increasing the aspect ratio will result in a taller tire:

Original wall height (from rim) = 245 x .70 = 171.5mm
New wall height = 245 x .75 = 183.75mm

Difference in tire diameter = (183.75-171.5) x 2 = 24.5mm = 0.96 in

Thus your rolling diameter will increase by ~ 1 inch. This can make your speedo and odo register slow, i.e., you will be going faster than whan the instruments indicate. Changes to rolling diameter of 1-2% are usually acceptable. To keep the same rolling diameter, decrease the tire's width by 20mm for each increase of 5 in the aspect ratio:

Adjusted wall height = 225 x .75 = 168.75
Adjusted difference in tire diameter = (171.5-168.75) x 2 = 5.5 mm = 0.22 in