Geometric tangency vs. optical correction.

Hello, a question has come up regarding the tangency of the circles with the ground. In image 2, you can see how the circles are geometrically tangent to the ground. This shows a control of geometry in the linework, but something looks "off". I know this is typical in icon design and people make 'optical corrections'. In photo 3, the outline of the circles penetrates into the ground. Now it looks weird because the intersection between the circle and the ground creates a stroke width thicker than the rest of the lines, or a sort of visual clump/smudge (highlighted in red). In photo 4, the intersection is more subtle. I don't know if this is the best solution or if I should further taper the stroke width of the tire along the final degrees of the curve before it touches the ground. (I'd also like to ask whether the blue lines for the 'hedge' look odd compared to the rest of the black linework. I tried them in black, but they drew too much attention; however, in blue, they seem inconsistent with the other lines.)