It actually happened to me on 2 brand new cars

I Have A Pair On My Car Only Issue Was The Calipers Was Rubbing On in Inside Of My Wheels. Riken Mesh Put Stock Wheels Back On No Rubbing -_-

Rx7 Disks
 

You can use all of the FC parts with the FD caliper, including pads, rotors, spindle, and hub. The FD calipers is functionally identical to the FC one, except for a slightly more modern casting. I think even the rebuild kit is the same.

Mine bolted up fine (although I have a spacer between the hub and the rotor because I have 4 lug hubs), on a 5 lug hub they should bolt up without modification. In all fairness I haven't tested it yet, but all the parts bolt together and move as they should. And many others have done this before me with success.

EDIT: I should also mention that there is no advantage in function, only form. They look newer, but the calipers have no extra braking power (I think even the FD rotor is only 1/16 inch greater in diameter). If you're doing it for aesthetics or because the calipers are on hand, go for it. But I wouldn't go out and spend money on it otherwise.

A friend of mine and myself were debating this recently, oddly enough. I've never understood why I've seen and heard of so many people over the years going on about FD brakes over their previously 4 pot FC brakes. As far as I've always been aware, there is zero performance benefit.

In my opinion the FC 4 pots look more beefy from a visual standpoint. They're different from today's plain Jane smooth calipers.

I bought them because I was upgrading from single piston calipers, and because they were cheap and available. According to Rockauto they use the exact same rebuild kits, so I very much doubt there's any difference in piston size/depth. Also according to Rockauto, they use identical brake pads and springs. I know the FD rotors have greater diameter, which I find puzzling as the pads are identical. FC 4 piston front rotors are 277mm in diameter, and a series 6 FD's are 294mm in diameter (conflicting with the 1/16 inch difference I incorrectly stated above). Obviously FD's don't have 17mm of unused disc space, and the pads are the same and they don't hang off of my FC rotor, so I think the extra diameter comes from thickening the cylindrical wall of the hat portion on the FD caliper and spacing the caliper out further (unless I'm horribly misunderstanding something). They are both 22mm in disc thickness new, but the thickness of the hat is different. Either way, since the pad contact area is identical, the only benefit would come from better cooling due to greater mass (which I can't test, but assume would be negligible).

Visually speaking, I prefer the look of the FD calipers. I think the lines are a bit cleaner. However the bigger casting may interfere with wheel selection.

If someone happens to have an FD rotor and an FC rotor laying around to compare visually, that would be very useful. Considering this thread has been revived after several years of inactivity, it would be prudent to add as much useful data as we can.

I can confirm that the FD calipers make it easier to fit certain aftermarket wheels without wheel spacers as the FC calipers are quite bulky and can foul on the inner wheel.

It is correct that the calipers are functionally identical and use the same rebuild kit. The pads are also the same. However the pad hardware, anti-rattle springs etc are different.