Ok... When we got new overhead doors in the garage a few years ago
they put in all new hardware. Rails, springs, everything. I was busy
at the time, and had more money than time. Not so now, so please no
Nigerian banking scams.

Anyway, there are two doors. One is an 8 x 9 and the other is 8 x
16. The smaller one has a single coil spring on a standard overhead
door axle. The larger one has two springs. What is odd is that the
are not the same size. One is about the same size as the one on the
smaller door. The other is a good 14-18 inches longer.

Now if everything was working fine I wouldn't have even noticed, but
the smaller of the two springs on the larger door broke. Makes sense
since it would have less length to absorb the twist. My question I
guess, is there any "legitimate" reason why they would two different
size springs on a the same door axle?

I am not willing to just say, "Well they are the professional door
company. They must know what they are doing." They do not. The
rails, opener mount, etc were all out of square, and even the distance
between the rails from the header to the motor was off. I called them
back 3 times before I finally gave up and just fixed it all myself.

The unbroken spring on the larger door is much larger. I was
wondering if it might not be adequate to handle the door by itself. I
installed all the commercial doors on my shop (much heavier doors) and
I still have a set of door spring tommy bars on the shelf.