I need to replace the speakers (F&R) in a 1992 Civic, would anyone happen to know the factory size of all four?

 

I would go to www.Crutchfield.com and click on "outfit my car" under car accessories and add the info.

If I'm not mistaken, they're 6.5's

 

Mine's a '92 and they're 5 1/4

Pretty sure it's the same on all body styles.

You can easily fit 6 1/2 speakers in the back if you want, but you'll most likely have to be content with having only 1 (or 2 max) bolt holding them in place, or drill some new holes - being careful not to come down on any wires.

It would help if you got speakers with multiple mounting holes, instead of just three or four.

Even then you might want to get some padding to put between the speaker and the metal it's mounted to so you don't have issues with vibration.

edit: h: Or, apparently, you can just order them with the proper mounting brackets that will make almost anything fit. On the site that Chefboiali provided h:

 

Thanks for the link, that website lists them all four as 6½.

 

just be careful when u install the front speakers. i bought focals, and the speaker magnet was a little too big and the window would actually clip the magnet. so you'll need something to raise the speaker off the doo just a little bit