If you're talking about the fronts, I don't know when you got them or what kit you got, but I have Baer "track" 13-inch brakes on my Mustang, kit delivered October 2002, and before I got them I confirmed with them that they are interchangeable with any off-the-shelf Cobra rotors (in the front anyway), they said yes they are, and last night I consulted the Baer catalog I have at home that I got with my order which lists these rotors at 1.1 inch, matching most of the information I was able to find about Cobra rotors.
Now, most importantly, I just got off the phone with Baer tech line ((602) 233-1411) and they confirmed that the 13-inch rotors are indeed 1.1 inches. Hard to argue with the source. I asked if they ever had an application where front rotors were .875 and they said their old "SS" system (12-inch for Fox-style spindles) included rotors that were .810 inch wide, but no .875's
I'm not trying to be argumentative, I just want the correct information out there for anyone else who stumbles on this thread. My suggestion is you do some real digging into exactly what you have before you blow a wad of money on what may end up being a direct replacement. Because the Baer 13-inch rotors ARE essentially Cobra rotors, as I've been saying.
If you're talking about the rears, they are Corvette rotors with a Cobra bolt spacing so no, they are not off-the-shelf interchangeable, and in addition, the calipers present a clearance issue with trying to use a lot of off-the-shelf pads on the supplied rotors; as I found out the hard way, they require a pad that's thinner than you're likely to find OTS. That's why Hawk makes a pad specifically for Baer "tour" kits on Mustangs.
