Discussion
I currently have an Audi S6 with 19" wheels with a width of 8.5" an an offset of 45.
I'm looking at changing them to a 20" wheel width of 9.0" and an offset of 42.
Does this mean that the inner face of the wheel will be 3mm closer to the hub and brake caliper because the offset is 3mm smaller? I only ask because the gap between wheel and caliper is tight enough on the existing 19" wheels.
I'm looking at changing them to a 20" wheel width of 9.0" and an offset of 42.
Does this mean that the inner face of the wheel will be 3mm closer to the hub and brake caliper because the offset is 3mm smaller? I only ask because the gap between wheel and caliper is tight enough on the existing 19" wheels.
The et distance is measured from the centreline of the wheel, and a smaller et means it sticks out more.
Your new wheel has a centre 3mm further out, but it is 1/2 inch wider (12.5mm) so the inner face ends up 3.25mm further in.
The outer face of the wheel will be 9.25mm further out (3mm from the et change and 6.25mm from the extra rim width).
So you are right in that the inner face is about 3mm closer to the strut but not for the reason you thought.
The app I use to check my calculations (tire size calculator) shows the new wheel as having an inner face 3.3mm closer to the strut and the outer face 9.3mm further out.
Your new wheel has a centre 3mm further out, but it is 1/2 inch wider (12.5mm) so the inner face ends up 3.25mm further in.
The outer face of the wheel will be 9.25mm further out (3mm from the et change and 6.25mm from the extra rim width).
So you are right in that the inner face is about 3mm closer to the strut but not for the reason you thought.
The app I use to check my calculations (tire size calculator) shows the new wheel as having an inner face 3.3mm closer to the strut and the outer face 9.3mm further out.
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