My original Cruise America "wheel covers" kept falling off. Originals did not require a wrench to remove. Originals were like a big hub cap, just snap on and off.
Then I actually got "wheel simulators" that are held on with a lug nut and coupling nut, that does has have a dimple in it. Those don't fall off.
Different sizes available, so make sure you get right size. I also have the "pliers" type, but they are not as strong.
http://www.pacificdualies.com/31-2000lw-lug-nut-wrench/http://www.campingworld.com/browse/skus/index.cfm?skunum=6837&rewrote&affiliateid=5193&gclid=CJXyjczIuMsCFRSPfgodLJQDQw
