Select the green edges and scale them down a little to make the points a little narrower.
Select the polys that are shown in red and inset them using the "Inset" tool by a value of about 2.
Rearrange the vertices around the inset polygons and arrange them in the shape of an octagon. An easy way to do this is to create an 8-sided n-gon and position it in front of the rim and the use that as a guide for where to place your vertices. The reason you do this is to get a perfect circle when you smooth the geometry. Now do the same thing for the other four. Now select the edges shown in green for and chamfer it by 0.5.
Select the polygons shown in the picture the extrude them outwards by about 1.5. Now delete the polygons in each circle and delete them to make the holes.
Select the green edges shown and extrude inwards to create the polys shown in red. Adjust vertices to get a good shape. Now select the polys you just created and extrude them outwards by 1.5 to create a ridge around the inside of the rim. The rim is now complete. You can now unhide the hubcap.