If your rear hub looks like this, then you can leave the cap off.
But if your rear hub looks more like this front hub, then you're being dumb not to put a hub cap on it.
I'll just add a pic of an original-style Cobra rear hub that
does not need a cap on the outside -- for obvious reasons. This hub would not fit my beautiful ERA outboard braked rear, nor any other Cobra that I have actually touched with my fat sticky fingers.
