Do we need of a top head set plug?

[carbonazza]

I saw this build for Marek Konwa a Polish racer for the Olympics.
http://veloart.pl/en_project-29-konwa.html

If you look at the picture of the headset, there is no plug at the top.
To my surprise there is no plug to my Cannondale Rush either, just a plastic cap.

Is the plug just an extra security thing?
Anybody else riding without it?

[SamSkjord]

You need it to preload the headset but after that the stem keeps everything nice and tight, only issue is in a crash where you need to put the stem back straight. But, given the build list of that bike I don't think that's something they're worried about.

When rebuilding mine I use two top caps;
First a preload the headset with http://www.chainreactioncycles.com/gusset-universal-headlock/rp-prod17766
then the lefty holds everything nice and tight regardless of whether I have a stem on or not so I have a much lighter one on for riding just to save my sternum.

[carbonazza]

Interesting. Thank you for the information.

[Vipassana]

SamSkjord is spot on.  I've ridden extensively without a top-cap in the past.  I keep one on though for esthetics.  Bike shops in various places used to have custom ones with laser engraving of a city/town/trail/park nearby or even just a funny expression, but I don't see that as often these days.

[RS VR6]

He doesn't ride with a bearing cover either.