Biggest rotor you can fit on a stock 73 A disc knuckle ?

I see many kits for drum knuckles. Maybe this is because most cars need the conversion?
I have the 1975 Dart knuckles in my Charger. The rotors are the 11.75 Cordoba discs. I've wondered about increasing the rotor size but don't recall seeing anything listed for disc knuckles.
What have you heard ?

15" front talk with Magnum Force but that is a 6 piston. You can go to 12.19 with 4 piston with the Wilwood kits. I'm not sure on other kits.

Your wheel diameter will limit you, not your spindle. (at least when it comes to making mounts for what ever rotor and caliper combo you'd want)

Thanks. I have an 18x9 front wheel. I thought the common belief was that the rotor usually has to be 3" smaller than the wheel diameter.
No, I do not need a 15" rotor to stop the car, I was just wondering and mulling the options.

Would depend on your wheel design too along with how high your caliper sits up off the rotor. I have 360mm rotors with Brembos and they clear my 18" rims...but not a ton of room to spare.

The wheel shell and spoke design also play a roll on caliper/rotor offset. If the rotor has enough inset you can fit more common off the shelf wheels.

what about some aggressive nascar pads & a breakin (bed in) procedure. it'd be the easiest upgrade.

Nascar pads?

Nascar pads, if truly for Nascar applications and not just a gimmick name, are designed for serious high speed and high heat applications, probably gonna be horrible on a street car. Ever see the video of the rotors glowing cherry red when they put on the brakes during a race?

Race pads on street = Front end body work

It depends on the shape of the parts but back when I was building 13" brake kits they were all designed to work with Ford Mustang 17 inch rims. So if your 18" rims are caliper "friendly" then you should be able to put a 14" rotor in there. A 13" rotor with a big caliper should easily fit inside an 18" rim unless you have the world's worst wheel design.

I believe the SuperSpeedway pads often have a low temp usefulness and aggressiveness, since they are seldom used, but hugely important for pit stops, and cooled constantly by high speed air. I suspect we are mainly talking brake compound selection, as the hardware is super expensive, even used.

This is the Dr Diff cobra kit (13" rotor) with an 18x9. Just bolted it on, its an easy swap, but haven't driven the car yet. If you wanted opposed piston caliper you would need rotors with a deeper hat (more offset to the knuckle side). The wheels are Torque thrust M's, which are basically mustang wheels as well.

There are a lot of pads available for this application (94-04 Mustang Cobra). I also bought the rear kit (11.75 rear disk that is vented), but haven't started the install yet.

Looks good. That is a really good "bang for the buck" way to put big rotors and good wheels/tires on a Mopar. You'll notice a big, big difference compared to the factory setup.

How much benefit is there going from the Dr Diff Stage 3 kit with the Cobra calipers and the 4 piston Brembos on the Stage 4?

Don't know, but mine stop pretty well with manual brakes. Sorry, I don't have a close up.

Yep, I've got the same 13" kit from Dr Diff but with 17x8 in front, 18x9 in rear. The rear are his 13" kit as well. Hopefully I get to stomp the stop pedal later next weekend, the car isn't on the road yet.

You have a 13" rear brake kit? I didn't know anyone offered anything that big for a rear brake setup.

Yep, a 13" rear kit! I bought the kit from Dr Diff back in early 2008, but looking at his website this morning it doesn't appear as though he offers it any longer.

Here's a poor pic w/ wetsanded quarter panel, but they are the Cobra rear calipers w/ parking attachment. I believe the rotors in this kit at the time were Porsche.

Here's a better pic of the 13" rear disc assembly, sorry about the tarnish!

Yeah, those kits are gone. I believe they were SRT rotors, but don't quote me on that.

What was the bore size of the caliper?

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they would not be porsche rotors, porsche does vented rotors out back on everything from the late 70's up (except the 924).