i got the 3 ft wilson flex and it has hit my garage door once when it was still opening alittle but it still works great i would suggest mounting it lower

 

I solved it with a bungee cord.
I have a 4.5 ft Francis fiberglass antenna and the Teraflex mount on the spare tire mount.

Solution: I use a long bungee cord with plastic hooks to bend the antenna over and hook it to the rear door handle. Bend it only as far as needed to clear the door. Wrap the bunge around the antenna about 2" from the tip. If you wrap around twice and hook it to itself it doesn't slip on the fiberglass antenna like you might think it would. If you also wrap it twice around the door handle and hook back to the cord it won't mark the finish of the handle or door.

It now clears the door no problem and take 2 seconds to remove or replace if I want maximum range from my CB. Stays on fine at highway speeds and CB stll works, just cuts range a little.

-Ray (wwiifirearms.com)

 

I have a 3' and I hit my ceiling, but I have a bulk head that contains duct work that hangs down. I have mine on a teraflex tire mount bracket, im going to try to flip it upside down or something...I just need about an inch to clear everything...

 

I have the same problem. Running a 3' firestik that hits the garage. I need to take some measurements and see if a 2' will clear it. Then keep the 3' for trail runs

 

Don't bother trying to move the Teraflex mount from the upper right of the tire carrier to the lower left, it doesn't work.

I tried solving my garage door issues this way, but then the tire hits the antenna mount and you can't get the tire on correctly. It appears the tire carrier has a slight cant to it so it works on top but not on the bottom.

Try the bungee cord.
-Ray (wwiifirearms)

 

this is the one that i use because i had the same problem

 

mine does it... i take it off before entering otherwise there is a horrendous banging noise and the last time i forgot it striped the threads on the adapter when it was bent out of there.

 

Both my VHF and HF antennas hit the garage unless I take the whips off. To make this easier I made some thumbscrews to replace the allen head set scews. I just make sure the ATAS 100 is tuned to 14 Mhz or higher so the coil will clear the garage door and then remove the whips. Takes all of 30 seconds. I place the whips along the floor on the drivers side. While I am replacing the whips it gives me a good opportunity to inspect the rest of the antenna installation on a regular basis/

 

Get a Wilson Flex ant, it will go right in and out with no problem. The Wilson Flex can pretty much be flexed in half, try that with a Fire stik.
http://www.wilsonantenna.com/fg.htm#flex