However, (1) The brake dust builds up on the inner wheel anyway, so about once a year you need to take off the wheel and wash it . I believe that MB says to clean the wheel every so many miles or when you do a certain maintenance or something, anyway(even without covers). And the caliper gets dusty, either way. (2) My '87 wheels are more of a closed design, so the covers are almost impossible to see. Some open designs wouldn't look too good, though. (3) You are right that brake dust is nasty and corrosive. That is why I put the covers (vented) on in the first place. After about 16 years, the wheels still look like new. (4) Finally, when I read how fast some people go through pads and rotors, maybe they shouldn't use dust covers!