The driver's rear hubcap on the car. Note the 6 Allen head bolts holding it on.

Note that it stands off of the rim a bit. I did this to make it easy to remove by hand, and to make sure that air could get through/out of the rims.

To remove, I simply grasp the hubcap as shown, with 2 hands, at 2 adjacent spokes on the rim, and pull gently until it pops loose. To install, I place the hubcap on the rim, and hit the hubcap directly over each Allen bolt until it locks in place.

The hardware stack, top to bottom:

• 10-24 3/8" long screw
• 3/16" x 1" fender washer
• hubcap ring
• 10-24 washer
• 3/16" x 3/4" coupler nut
• 10-24 washer
• hubcap
• 10-24 x 1/2" Allen head bolt

Total cost for hardware to mount the hubcaps was less than $30. The hubcaps were $25-30 for all 4.

To clear the rim, you need to grind down the fender washer as shown. I also ended up using this system with the coupler nuts, as Allen bolts all the way through to a nut on the back side (on top of the fender washer) resulted in rubbing on the rim if Nyloc nuts were used. This system also makes sure that the spacing is even all around the rim, where using longer Allen bolts and spacers requires careful trimming of the spacer length to maintain an even gap.

To make sure nothing comes loose, I used Blue Loctite threadlocker on all bolts/screws.

So how did I figure out where to drill the holes? I just looked over the rear of the hubcap ring, trying to get the bolts as close to the ring retainer posts as possible, but still maintain clearance for fender washers, to spread the load on the stock plastic hubcap ring as much as possible when pulling on the system to remove it.

To get all the holes in the same places, I placed masking tape over each hubcap ring right over where the spokes of the rim would be (the pictured area). I then got a clear ruler, ran some masking tape over it on the areas that matched up with outer rim at the pink lines shown. Then found the center between them, put some masking tape there on the ruler, and marked that center. Then I simply lined up the outer masking tape edges with the pink-lined areas on each section of the hubcap ring, and marked the center point on the masking tape on the ring. I then repeated the process for the bottom (blue lines). Then I connected the marks on each "spoke area", resulting in a center line in line with the center of the wheel/hubcap ring. Then I measured 1.5" in from the outer edge of the hubcap ring, marking the intersection with the center lines previously drawn (roughly where the green circle is). Then I drilled each cross spot with a 3/32" drillbit, then with a 13/64" drillbit.

To get the holes in the right place on the new hubcaps, I taped each one to a stock hubcap ring that was already drilled, centering it as best as possible. Then I placed the whole thing upsidedown on an old phonebook, and used a drill with a top level on it to make sure I was drilling through the hubcap ring holes perfectly vertically into the hubcap. It worked well enough.

I used black-oxided Allen bolts initially, and they rusted. FAST - they looked like this after about 2 days.

I managed to find button head stainless steel Allen bolts at a local small hardware store finally (I originally wanted to use them, but couldn't find them at Lowes/Home Depot), correcting that problem and getting the look I wanted.

Note, however, the difference in color of the "hubcap" in this pic and the last - these pizza pans discolor quickly (and unevenly), so if you decide to install them, I'd recommend using Liquid Sandpaper paint remover to remove the nonstick finish, then priming and painting them to the color you wish.