Scion TC

What are the right statistics that I should get for 18in rims on a 06' Scion tC?

I own a 06' Scion tC and I want to get some 18in rims on it and I know that you need the correct information before you buy the rims. So far I know that the Scion tC has a lug nut patter of 5x100 but what is the correct offset that I need? 20? 42?

The correct offset will depend on the width of the rim. For example, the stock 17 inch rim has a width of 7 inches with an offset of +45. If you buy an 18 inch rim with a width of 7.5 inches with an offset of +38, your inner clearance will be 1 mm MORE and outer position EXTEND an extra 13 mm (which will position the wheel to be more flush with the fender). In my experience, you don't want to extend anymore than 13 or 14 mm or else you will have clearance issues and you will have rubbing issues (especially if your car is lowered) and added stress to other components such as the axles.

Please visit the links below for more information!

Help you determine clearance for the offset you choose:
http://www.1010tires.com/WheelOffsetCalculator.asp

Help you determine which tire size will BEST fit the rims. It provides vital information such difference of your speedometer in comparison to stock:
http://www.1010tires.com/TireSizeCalculator.asp