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Center Cap Depth (all wheel sizes):
The RPF1 has a unique design compared to other wheels which may cause the axle, axle nut, or other parts of the car to protrude through the center hole of the wheel. These caps allow 5mm of protrusion before the part will contact the cap and prevent it from seating in the wheel properly.
For example, the axle nut on any NA/NB Miata protrudes too far when using the 15x7 +41 wheel for this cap to work. However, this issue does not exist for 15x7 +35 wheel on NA/NB Miatas.
** Any issues with parts of the car contacting the center cap can be rectified with spacers. **
Our caps will not work with centering rings for this spec of wheel only. There is extra depth to the "teeth" that grab the wheel they will occupy the same space that a centering ring would.
These wheels can still be used safely without centering rings, they are merely a device to ensure proper alignment when mounting the wheels. All RPF1s use conical lug nuts which ensure the wheel is perfectly centered on your studs as they are tightened.
Some solid centering rings will interfere with the "teeth" of the center caps preventing them from properly engaging with the wheel. The centering ring must have a thin wall, or have a groove to allow space for the center cap tooth.
As with the +41 variant, these wheels can be safely run without centering rings.
Centering Rings with 15x8 +28, 16", 17", and 18" Wheels:
There are no issues running center caps with centering rings any other size/width/offset wheel other than the 15x7 outlined above. This includes all types of centering ring.
If you have any questions about the above information please use the contact us form at the bottom left of every page to get in touch!