[KTL]

This front caliper tends to create a lot of uncertainty. It originated on the 928 S4 (and the 959) and then appeared on the 944 Turbo with the optional M030 setup, which eventually became standard on the 944 Turbo S. They use the 304mm rotor. The early S4 calipers have 42/26 pistons and then eventually they all were made 44/36.

Along comes the 964 Turbo & 928 GTS and the confusion really begins when the slightly larger "big red" calipers appear, which were also black, and used a larger 322mm diameter rotor. The 993 comes along and uses the smaller S4 caliper with the 304mm rotor and the 993 twin turbo uses the larger big red with the 322mm rotor for more confusion. I'm sure there's some other Porsche model nuances i'm missing......

The S4 size front calipers can definitely fit under 16 inch wheels. I had those S4 front calipers fit nicely under both the BBS RS 3-piece street wheels, as well as under the more vanilla BBS one piece wheels. The only 16 inch Fuchs i've seen them fit under is either with spacers or the three Fuchs wheels that have deep hubs for brake clearance- 944T 16x7, 944T 16x8, 930 16x9

That rust line on the rear rotor OD is odd because it's hard for me to think that the top of the pad is below the OD of the rotor. In that case the rotor OD usually wants to hit the "roof" of the caliper. Often we see the reverse situation where the caliper isn't sitting down far enough on a smaller diameter rotor and that puts the top of the brake pad above the rotor OD, leaving you with a sliver of untouched brake pad around the top.

On the typical 911 pre-964 aluminum trailing arms we're familiar with, I have found an unlikely rotor that can be used in lieu of the 930 rotor is the 299x28mm 964 FRONT rotor. The hat ID is a perfect fit to the older 911 axle hub OD and therefore registers perfectly. The hat offset is very close to that of the 930 rear rotor. 930 rear is 80mm from top of hat to far side of rotor face and the 964 front rotor is 83mm hat to far face Only caveat is that you have to ditch the entire parking brake assembly and lop off a piece of the trailing arm that serves the parking brake cable route.

So my point is that if the 930 rear rotor is what's currently on there, you may want to test fit a 964 front to see what that does for you. That is, assuming you don't have any issues with parking brake back there since it's a racecar? The 964 front is not as elegant as the 930 that has directional cooling and drilled/cast holes. But it's a beefy SOB and can certainly handle the abuse of racing. One could argue it's a bit more durable than the 930 since it doesn't have the holes in it which tend to promote cracking? 930 rotor is a great rotor nonetheless. We've used them for years with no problems.