No work on bike today due to Garage Door issues

[McCabe-Thiele (Ted)]

Our Henderson Double Canopy Garage Door is just over 30 years old - the door has a steel galvanized frame with an alluminium skin.
The door was electrified by me some 28 years ago - I purchased a Chamberlain Electric Door Kit out of the Sunday Times for about £150.
For some strange reason the door has started hitting the concrete base with the mechanism groaning and juddering  when its opening fully - I can't see any obvious reason for the fault developing aside from wear in the central curved convertor arm rollers.

Two firms have said I need a complete new door but I'm not convinced that it can't be fixed as my door is in great condition. When I dismantled the central door arm I found that two of the four nylon rollers were worn like a threepenny bit.

Today I fitted a later door arm - an obsolete new stock later item by Chamberlain designed for older doors. The door mechanism works really smoothly now with all the judder gone. I've adjusted the closed door position to prevent it striking the floor.

Plan A is now to see if the local "no fix no fee" door repairer can sort out the drop - its only a few mm so I hope he can adjust the spring loaded mechanism and thus sort it or some other magic.

Plan B is to get the Disc Cutter out to cut a pair of grooves in the concrete base then power chisel out the concrete in the gap.

Anyone here had similar door drop problems ?

[Green1]

I have a Henderson double door aswell. Always ment to stick a motor to it at about 14feet long its a heavy lump.
The door has been opened and closed at least 4 times a day seven days a week for the past 30years.
My door has dropped in the middle aswell but its well past its best it has wear on one roller and the holes in both hinges where the springs attach have worn right through the bronze bushes and about 10mm into the hinges. 
Check the condition of the hooks on the ends of the springs they go with a hell of a bang when they snap and hurt like hell when they stick the spring in your legs.
Over 30 years it has had countless new locks,three springs and five spring hooks and now it needs two hinges,spring hooks and rollers.
I think it may be time for a new one.