Originally Posted by
spock
Valve cap is useful as it keeps dust out. If dust gets into the inner workings, it might cause the valve to leak very slowly because the little dust particles might prevent it from closing completely.
If you take them off, wheels will all-encompassinlgy be lighter tho' .
Presta valves already have a dust cap built in to them. You close the valve after you put air into it and no dust can get in.