Srry to be a newb but what is offset. I always here about people get new rims or tires and the offset comes into play like 20 by 9.5 or something like that.

 

20 by 9.5 is not offset.

20 is the size\diameter of the rim.

9.5 is the width of the rim.

Offset is easier to explain with a picture but I'll try explaining with words.

Offset is how much the wheel sticks out beyond your hub\axle. Here's a visual of what I'm trying to say so if your standing and looking from the back of your car towards the front of your car, your wheel would either stick out past your body or is tucked inside the body. Your offset determines how much your wheel is tucked inside or past the body.

Get it? If not perhaps someone else can explain it more easily in words.

 

It's how far (+ or -) the mounting surface of the wheel is to the center of the wheel. That probably doesn't help unless you can see a pic. A pic is easier to understand.

 

I did a quick search and found this site. http://www.wheelsnext.com/content/wheel_tech.html

It has some pics which may help you understand a bit.

 

cant explain it any more than that... refer to the link he gave u

 

like everyone has been saying offset deals with how far the rims will stick inside the wheel well or stick out
the closer you get to 0 or negative offset the more the rims sticks out of the wheel well
the more positive you get the more it goes in.
stock offset pretty much puts the rims in the middle of the fender and inner wheel well, but not always.

lets say your stock rim is 17x8 with an offset of +55
and you want to get wider rims lets say 18x10 +65 in the back
if +55 is centered and you install these rims since they are way wider than stock
they will more like rub your inner wheel well and supension system.
now for you to clear the inner wheel well you would have to lower the offset in which having it instead of +65 to let say +45 which clears the inner wheel well but will more than likely stick out of the fenders. This situation is a fixable by rolling and pulling the fender, if its not enough add some negative camber, still not enough cut the fenders and add overfenders.most of the VIP gurus do a lot of rolling and extreme pulling and a lot of negative camber as well. if you find yourself getting rims with to much positive offset you can also fix that by getting wheel spacers.

hope this helps...ask if you have anymore questions
i'll answer them to the best of my abilities
or some other knowledgeable member will help too

 

http://www.tirerack.com/wheels/tech/...jsp?techid=101