3D-Printed 14×7 RPF1 Center Caps

Enkei doesn’t make center caps for 14″ or 15″ RPF1 wheels. There are some options available for 15″ wheels (apparently Konig Helium center caps do the trick), and nice aftermarket options like the ones from Flat Out Graphics. If you’re like me, you open that link and drool at the center caps you wish you could have for your 14’s. But anything is possible with a 3D-printer, right??

Why is this a problem in the first place? For reference, here is a close-up of the center bore for a 15×7 RPF1 on my Miata back in 2017 compared to a 14×7.

15×7 Enkei RPF1 center bore
14×7 Enkei RPF1 center bore

See that stepped lip around the center bore? A regular wheel center cap isn’t going to click in all the way. The diameter is different too! And to make things even worse, look how far that axle nut sticks out!

Axle nut protruding from wheel face

Here are the critical dimensions I was able to measure after many, many, many iterations of testing. The main insert needs a diameter of about 65mm, and to catch the groove in the wheel the prongs need to be about 4mm in from the face. If you can find a center cap something like this, it might work!

Center cap critical dimensions
Center cap 3D model

Batch of center caps off the 3D-printer

After printing off the plastic center caps, the first major task is to smooth down the layer lines. There are better guides for how to do that, and maybe acetone smoothing with ABS would have been the most effective, but I opted to use glazing spot putty and sandpaper. After struggling with the first one, I designed a clamp/wedge so that I could mount each center cap in the drill press.

Center cap mounted in the drill press for smoothing
Center caps before and after spot putty sanding

You’ll notice the plastic color change from pink to gray, and some small design updates. After putting the first batch of center caps fully though prep and paint, two of them were tragically lost. I took the Miata for a drive on a cold day and somewhere along the way they popped out of the wheels and rolled away forever.

Taking a nice bikini top photo on the exact drive when two center caps were lost

The pink plastic is PLA, and for version 2 I switched to PETG which is slightly more flexible and more durable. The “tab” design is also better which has kept version 2 on the wheels securely.

The next difficult step in this process is trying to find a paint combination that will work well with the bright silver RPF1s. The best color match I could make was:

  1. Flat gray primer to find any issues in the smoothing
  2. White base layer
  3. Rust-oleum high performance silver wheel paint (for the big metallic flakes and deep silver undertone)
  4. Dupli-Color Bright Silver Metallic BCC0410 in thin coats to brighten the color and add *sparkles*
  5. Crystal clear enamel for gloss and protection
White base color on center caps
Silver wheel paint over white base layer
Bright silver automotive top color coat

After gloss clear coat, the last step is to apply some Enkei domed epoxy stickers from Flat Out Graphics.

Final caps v1 ready for stickers
Final paint finish (and some rejects)

Finally, the center caps can be popped into place on the wheels, with the Enkei logo nicely aligned with the lug nuts. This project was a long journey, but I’m proud of the final results!

14×7 RPF1 before and after center caps
Clean custom 3D-printed center caps
Flat Out Graphics – Center Cap Decals (Set of 4) – 50mm$35
Dupli-Color Perfect Match 8 Ounce Bright Silver Metallic Spray Paint – BCC0410$17
Rust-Oleum 248927 High Performance Wheel Spray Paint$11
Bondo Glazing and Spot Putty$10

2 Comments on “3D-Printed 14×7 RPF1 Center Caps”

  1. Great job, would you be interested in selling a set of these? I would even be willing to buy a raw pair. Don’t own a 3D printer 🙁

    1. Thanks Victor! My print quality isn’t great which is part of the reason the sanding and finishing was so much work. You could try one of those 3D print services that prints and ships uploaded files. Probably not too expensive to have a set printed in PETG or even ABS plastic.

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