uneven garage door closing

[pudgybear]

checked the floor with a long 2x4 straight edge and it appears to be somewhat straight and level yet when the door closes the is a GAP under the left side - My question is could the wire cable be to tight and holding up the one side? maybe if i took the cables off maybe i could see if the door set flat! any ideas how to close up the gap?

 

[6t7gto]

Put a pipe wrench on the spring shaft and slacken the cable a little.
If the gap closes, you know it is the cable causing the problem.

David