Reading Wheel Sizes:
Example Size: 15x7 4-100 40S
15 - Rim diameter in inches.
7 - Width of rim in inches.
4-100 - Bolt Pattern.
4 - Number of lug holes in wheel.
100 - Distance between lug holes (in millimeters).
Some wheels have multiple bolt patterns.
15x7 4-100/108
This wheel fits cars with both 4-100 bolt patterns and 4-108 bolt patterns.
40S - Offset and finish
40 - Measures in millimeters how far back or forward the mounting surface (face) is from the center of the wheel.
*Info from
http://www.discounttiredirect.com
Hope this helps!