One hubcap keeps falling off. I used a rubber mallet to make sure that the hubcap was on all the way around. Even driving slow (less than 20 mph) the hubcaps falls off. Neither the hubcap nor the rim have any apparent damage. Your help would be appreciated.

 

Welcome to the forum.

Have you tried switching that hubcap to another wheel to determine if it's the hub cap or the wheel that is at fault?

 

I had not done that yet, but I will.