offset question

[tripulldee]

I'm looking into getting new rims for my 2000 328i, and I noticed that the ones I'm interested in come in 2 diff offsets; 1 is 20mm offset, and the other is 40mm offset. What is the difference and how do I know which one I should get or would fit?

[Jeron]

Here is a good description of offset:

http://www.tirerack.com/wheels/tech/offset.htm

Also some wheels have the offset stamped on them. It will appear as ETXX or EXX where the XX is the offset. Yours may be E20 for a 20mm offset.

Jeron