the last number, in this case 8, is the diameter of the rim (or wheel, whatever you wanna call it). The rim also happens to be 8" wide, so you can fit tires from about 9" to 12" wide on them no problem. In your case, the second number, 10, is the width. Dont' be afraid to go an inch or two wider. And obviously, the first number is the diameter of the tire.