ok so when i tire size say something like this.. 305/123/20.. what does the 305 mean? is that like 35 inches or like how do you know how tall the tire is? help pleasee im a yungin barely getting a truck

 

Well, you are way off on the second number. A better example would be something like a 305/55-20. 305 is the width of the tire in millimeters. 55 is the aspect ratio, or relationship of the tires height to it's width. And of course, the 20 is the rim size. There are tire conversion tables online or you can look up the actual height and width on the tire manufacturer's website. But in this example a 305/55-20 would work out to be approximately a 33x12.50-20 in floatation size.

 

lol imagine if that number was correct. the tire would be wider than it was tall!