Wheel dust caps fell off! How to secure back on?

[Anthony Gee]

My rear wheel dust caps fell off, on my B14. I put on a cheap set of steel
wheels that didn't fit properly I guess, which made them come off..
Nevertheless, when I put them back on, they are not very snug, and they
come loose while driving I believe causing a consistent almost dinging
sound.... So I would like to get rid of this sound, and also make sure my
wheel bearings still get protected... how are these held in stock? Someone
suggested me to use a rubber mallet to put it in, but I'm not sure if I
damaged mine, but malleting doesn't really do anything for me... it still
falls out just as easily..

Thanks,
Anthony
agee@ucla.edu