I agree that in most cases, cross drilled rotors are at the very least unnecessary. At worst, the holes become the location of cracks that form in the rotors over time. Super-hard pads are not a good idea on the street either. Sure, they wear more slowly, but they can eat rotors instead of pads! Also, hard pads can be somewhat dangerous on a street car. This is because they are not very effective without getting heated up first. In a road race situation, this is fine. The brakes are used with a vengeance and are always hot. On the street, however, you rarely get into a situation where the brakes always have enough heat in them to be at their best and this can cause sketchy brake performance that you may not be prepared for. I have only overheated brakes once on the street (In my Nissan Frontier) using regular pads but it was on a run of 7 pizza delivery orders-all of which were late, and I was rushing too much. ( I had 8 complaint calls on my driving in 15 min...) Consequently, I boiled the fluid out of the calipers and lost braking! At that moment, the harder pads may have been better as they would possibly not have been as stressed by the hard stops I was doing back to back and maybe not have built as much heat, but that's just speculation.
Anyhow, rear discs are nice, but your money is better spent on upgrading the fronts first rather than a swap to rear discs with stock fronts. The fronts do most of the braking and thus have more heat to dissipate. This is not to say there is nothing to gain with rear discs, just that they are not as critical as the fronts.
As far as rotors go, thicker rotors are better than thin ones, and larger diameter rotors are important for several reasons. Most importantly, larger diameter rotors have a greater mechanical advantage than smaller ones, thus multiplying the work the caliper does for a given amount of application pressure. Plus, they also have more surface area and dissipate heat better.
For the record, My Cutlass currently has stock brakes, but I am planning inexpensive upgrades in the future starting with the
B body 12 in fronts and finishing with 4th gen F body rear discs. The fronts are easy, but the rears will require a little fabrication-nothing I am incapable of doing though. Yes, I am aware of the negatives and the other things I need to finish this so there is no need to post them.
