Everett M. Greene writes:

The number of turns = door height / (drum diameter * pi).
Should be about 5 for most doors.

WRONG.

If you start with the door in the full up position, you
can get everything connected without tensioning the
springs.

WRONG AND HAZARDOUS.

At:

http://www.truetex.com/garage.htm

See the section on "Why Can't You Install the Springs Unwound, with the
Door in the Up Position?".