wanted: hangar door tips

Our EAA chapter had a 40' hangar door that split in the middle and
folded sideways (each half). The ends were hinged and the center had
a single roller that ran in a track above. The bottom was not
attached in any way and just hung. It was held closed and open with
large steel pins that dropped into holes in the concrete/asphalt.

The door worked OK but sometimes the bottom would scrape (seasonal)
and be hard to close and the door also "racked" if you pushed it wrong
(it would "rock" back and forth and cause it to open sort of "jumpy").

The trick is that this door was about as inexpensive a design as them
come so I want to use a similar design on a hangar I'm building.

What I'm needing are ideas for making this style of door operate
smoother (not rack) and prevent catching along the bottom with changes
in weather.

Any tips from those of you that have built or used this style of door?

Thanks folks.

J oa