the offset of the standard wheels is ET45 or 45mm standard wheels are 195 wide If I change to 215 wheels which are 20mm wider I need to adjust the offset to ET35 so as to keep the centre of the tyre at the same point Is that correct
NO. Offset is measured from the center of the wheel. If you want the center of the wheel to stay in the same place (i.e. keep the scrub radius constant), then you keep the offset constant.
the wheels do sit out more the top of the tyre is inline with the bodywork, It may be an extra 15mm each side as calculated a 16" ET45 uk wheel with 195 55 16 is 15kg 33lbs a 17" 7J ET35 with 205 40 17 is 17kg 37.5lbs This is a lower than standard profile - standard would be 45
