I'm very confused about all the different number for wheels. and now have a couple questions! first im up grading to 37s so will a 8.5 be wide enough. right now I have liquid metal magmas and to my luck I cant find the bs or the off set. all is know it that it keeps the tire real close to the truck. the new wheels im lookin at are 20 by 8.5 with a bs of 5.93 and off set of 30mm. what is this going to do to the wheel and tire, push it out any maybe stay the same? please help

thanks ryan

 

What width wheel you need depends on the tire's width, not it's height. An 8.5 is fine for a 12.50 inch wide tire.
Backspacing is the distance from the mounting surface of the wheel (where it bolts to the hub) to it's rear hub. The OEM 17's and 18's are 7.5 inches wide with 5.5 inches of backspacing. So, the wheel you are looking at will stick out about 1/2 inch farther than the OEM wheels.