Rims offset can be quite complex and technical. Nonetheless, your knowledge in this concept will come in useful in selecting the right set of rims to fit your car when choosing your new or second hand rims.
Rims are not created equal. One variable is the position of the mounting face, or the back face, of the wheel. If the mounting face is along the centreline of the wheel, it has zero offset. If the mounting face is further away from the car, or nearer the curb, it has positive offset. A negative offset means the mounting face is nearer the car. For your information, most passenger cars are positive offset.
It is important that you do not replace your rims with something that is drastically different to the originally fitted wheel. There must be sufficient clearance between your wheels and suspensions. It is not a good sight to see your wheels rubbing against the suspensions.
On the rims you find in Singapore, there will be a marking either at the back or front of the rim which reads “ETXX”. ET is a German prefix “Einpresstiefe” (which means “press depth”). This is commonly referred to as the ET number and the two digits that follows “ET” is your rim offset in millimetres. For example, “ET40” means an offset of 40mm.