Obviously when someone speaks of 18's, 19's, 20's, etc. I know they are refering to the diameter of the wheel, and when they say 18x9 or 18x10, I know that the second number refers to the "fatness" of the tire, but once people start talking about offsets and backspacing I get lost. I don't know what backspacing or offset refers to. There's some other number that gets tossed around, usually a number like 235 or 255, I don't know what this means either. Can someone explain what all these terms and numbers mean?

 

Go here to learn about tires.

 

And here for wheels.