After looking at every possible avenue, I have concluded that the 93 Cobras all had vented 10.07" x 0.945" rear rotors with Varga 45mm calipers that use a D347/D545 brake pad (exactly the same brake setup as the 87-88 T-bird TC). I spoke with numerous Cobra owners, several Ford brake engineers and searched through all of the printed literature I could find.
I did run across a couple people who claimed to have had/have/seen 93 Cobras with solid rear rotors. One case of this turned out to be that the owner thought that vented meant slots in the face of the friction surface. In all of the other cases, the people could/would never provide me with a photo or any other substantial evidence. Just a lot of "Trust me".
I did discover a couple of interesting things along the way.
After years of harassment, we have finally gotten Hawk to start making pads for the 93 Cobra/87-88 T-bird rear brakes. The FMSI number is D347 or D545. The base Hawk part number is HB580. The pads are available in HPS, DTC-60 and Blue compounds.
The primary reason that OEMs use curved vane rotors is not to increase brake cooling. That is a secondary benefit. The primary reason is to reduce brake shudder. Normal straight vaned rotors only have support of the friction surface directly above and below the vanes. In between the vanes, there is no support. As the rotors heat up and cool down, and as brake pad material transfers to and from the disc, the friction surface starts to get waves in it. These waves cause a slight shudder when the brakes are applied. If the rotor has 28 vanes, then there will be 28 waves in the surface. The low spots of the wave are between the vanes, the high spots are at the vanes.
Brembo and Kelsey-Hayes have a joint patent on the use of brake rotors with pillar vanes. These are vanes that have a short radial length. They are many of them staggered around the rotor so that there are only very small areas of the friction surfaces that aren't supported. These rotors don't get waves that can cause brake shudder. The primary reason that most OEMs use curved vane rotors is to keep the rotors from developing waves in the friction surface. They don't care very much about the additional brake cooling, so they only tool up to make a rotor for one rotation and just use it on both sides of the car. Chevrolet did this with the C5 Corvette. Mercedes does it with all of its cars and almost all of the AMG models. This is why the 93 Cobra has curved vane rotors, but uses the same part on both sides of the car.
I did run across a couple people who claimed to have had/have/seen 93 Cobras with solid rear rotors. One case of this turned out to be that the owner thought that vented meant slots in the face of the friction surface. In all of the other cases, the people could/would never provide me with a photo or any other substantial evidence. Just a lot of "Trust me".
I did discover a couple of interesting things along the way.
After years of harassment, we have finally gotten Hawk to start making pads for the 93 Cobra/87-88 T-bird rear brakes. The FMSI number is D347 or D545. The base Hawk part number is HB580. The pads are available in HPS, DTC-60 and Blue compounds.
The primary reason that OEMs use curved vane rotors is not to increase brake cooling. That is a secondary benefit. The primary reason is to reduce brake shudder. Normal straight vaned rotors only have support of the friction surface directly above and below the vanes. In between the vanes, there is no support. As the rotors heat up and cool down, and as brake pad material transfers to and from the disc, the friction surface starts to get waves in it. These waves cause a slight shudder when the brakes are applied. If the rotor has 28 vanes, then there will be 28 waves in the surface. The low spots of the wave are between the vanes, the high spots are at the vanes.
Brembo and Kelsey-Hayes have a joint patent on the use of brake rotors with pillar vanes. These are vanes that have a short radial length. They are many of them staggered around the rotor so that there are only very small areas of the friction surfaces that aren't supported. These rotors don't get waves that can cause brake shudder. The primary reason that most OEMs use curved vane rotors is to keep the rotors from developing waves in the friction surface. They don't care very much about the additional brake cooling, so they only tool up to make a rotor for one rotation and just use it on both sides of the car. Chevrolet did this with the C5 Corvette. Mercedes does it with all of its cars and almost all of the AMG models. This is why the 93 Cobra has curved vane rotors, but uses the same part on both sides of the car.
