How Wheel Offset Works
Offset is the distance from the wheel mounting face to the wheel centerline, in millimeters. A smaller ET pushes the wheel outward; a larger ET tucks it inward. Width and brake/fender clearance matter too.
Positive and negative offset
Positive offset means the mounting face is outboard of the centerline; negative means inboard. Stock wheels are often +35 to +50.
At the same width, reducing ET by 10 mm moves the wheel about 10 mm outward.
Checking a wheel change
Backspacing = wheel width / 2 + ET / 25.4 in inches; it determines whether the inner barrel hits the strut or brakes.
Outer clearance also depends on the fender and tire swing while steering; wide tires with low ET are the usual rub.
FAQ
Is ET35 more aggressive than ET45?
Yes, at the same width ET35 sits about 10 mm farther out than ET45.
Can I reuse stock lug bolts?
Check bolt pattern, seat type and thread length; replace them if they do not match.