what is the offset of 318ti

[nodoubt911]

i see rims for example 18x8 40mm offset and 18x9 40mm offset and im assuming 18x9 are for the rear and 18x8 are the fronts but can someone tell me what is the offset and how much of a difference of the offset be and still fit good

another question how do you know if you have a ti, active, club sport, or sport

[tiFreak]

offset is anywhere between 30 and 40