Over time, the plastic tabs that secure your center caps may break (or be broken off by ham-fisted tire-change technicians, cough-cough). In any event, replacements are expensive, may be hard to find or the real reason you are here; you want to fix it yourself!
I searched the internet for solutions, to no avail and then it dawned on me.
I determined that I could secure the plastic center caps in place by using powerful neodymium magnets that would be attracted to the metal lug bolts/nuts that hold the wheels on!
The magnets I chose each have about 12lbs of pulling force and some center caps were more damaged than others, but as few as two magnets are enough to hold plastic center caps onto the wheels.
I know, brilliant solution, right?
Step 1: What You Will Need
1. A center cap with broken plastic tabs
3. some PVC stock (I had some 1/4" Palite trim board left over from a siding job)
4. super glue
5. a cardboard template of your center cap (for identifying the location of the lug nuts)
Step 2: Preparing for the Fix
I had one nearly totally unusable center cap (courtesy of the tire change technician) so I made a 1/2 circle template out of cardboard because my wheels only have four lug nuts (you can figure out how to plan for five).
I then cut the badly damaged center cap in half so that I could accurately measure the distance from the end of the lug nut to the inside of the center cap. I my case it was 3/8" give or take.
I ordered eight 1/8" x 3/4" disc magnets. Each lug nut has a nominal diameter of 3/4" so this would accommodate slight misplacement.
Using my "testing" cap I superglued a piece of the 1/4" PVC stock (Palite) to the back of the center cap and then glued the magnet to it. I used the cardboard template to ensure that the magnets were placed where they would make contact with the lug nuts.
Step 3: Testing
You can see in the profile picture how the PVC serves as a stand off for the magnet.
Step 4: Final Assembly
The full center cap shown had at least two of the six tabs broken off, so the tensioning spring was useless. Two magnets provide about 24lbs, of pulling force, the center cap adheres well to the lug nuts.
Step 5: Held in Place
You can see that the center cap fits as intended. I had to make this repair on three of the four center caps.
So far, so good. I'm not going to pull them off until it's time to rotate the tires. Then I will check how well the magnets have held. If they seem loose, I will hit them with some two-part epoxy. The PVC should never break free.