what does 38mm off set mean? im looking into buying these Rota Grid racing wheels but ive heard from people that they fit wierd cause of the offset.. i dont know what off set is..

 

this means there is 38mm from the back lip of the wheel to where the wheel contacts the hub of the car. this is also called backspacing

 

Uh, not quite. Backspacing and offset are different. Offset is the distance from an imaginary line dividing the wheel down the center, to the surface of the wheel that contacts the hub. TireRack has a somewhat rudimentary explanation, but they DO show a diagram. It might be enough to help you understand: http://www.tirerack.com/wheels/tech/offset.htm

The DSM boyz also have a pic that shows the difference between offset and backspacing (which they like to call "Rear Spacing") http://home1.gte.net/macross/offsetFAQ.html

The stock '95 Integra offset is +45mm, and using the same wheel width with a +38mm offset will move the whole wheel 7mm toward the outside, but by switching to a wider wheel, you can theoretically "move" some of the wheel to the outside and some to the inside thus keeping the centerline in the stock location but allowing the use of a wider rim. Using a wider rim with the stock +45mm offset will "move" all the extra rim to the inside where you may run into clearance problems with suspension parts. THAT's why you need to understand the offset whenever you change wheel widths from stock.