0.23: Landing legs have mass always, runway gear wheels don't (except in editor)

[hab136]

See http://imgur.com/a/9hVTX for proof.

The runway wheels (small gear bay) have mass in the editor, but not in flight (both down and up).

The landing legs always have mass - in the editor, on the launchpad, in orbit, up or down.

[Ravenchant]

This isn't exclusive to the gear bay. IIRC, struts and fuel lines are massless during flight as well. Dunno when/if a fix is coming, though.

[arq]

The landing gears are massless because in their current form they are very heavy (a set of 3 weighs more than a jet engine) and there is no good way to counterbalance them. If they had mass, they would be very tricky to use outside of atmospheres because of the CoM issues they would cause. They will likely be given mass (though perhaps less than they currently have) in some future update, when part balancing and tweaking is performed.

[numerobis]

They haven't had mass in a very long time, so don't hold your breath waiting for them to acquire mass. The rover wheels, on the other hand, do have mass.