There are not many OEM aftermarket rotor choices out there, especially for the 05s. Many manufacturers won’t make the investment because GTOs are produced in such limited numbers and result in low product sales volumes. The basic choices are solid (OEM), slotted, cross-drilled, or drilled and slotted. Cross-drilled rotors look great but they are not recommended since they will crack. It’s not a matter of if, but when and it will be sooner rather than later if you brake hard and often. Some manufacturers offer dimpled rotors that look like drilled but don’t have the risk of cracking. Don’t confuse holes in the rotors of a Porsche, which are cast into the rotor, with solid rotors that have holes just drilled in them. These two different processes for placing a hole in the rotor result in different characteristics – and a price to support the benefit of how Porsche manufactures theirs. The benefit of slotted rotors is debatable. Many say that the slots were more advantageous with the older brake pad compositions that used to generate gasses during the braking action but are not required with modern brake pads. The slots do provide better action in the wet, look better, do provide some braking advantage, but also wear out pads quicker. I have tracked the GTO in the rain and not seen an issue with solid OEM rotors. A fellow I work with has two Ferraris he races. Cross-drilled are a definite no. He uses solid rotors and does not feel disadvantaged.
FYI, at the time of this posting, I've looked but have been unable to find OEM slotted rotors for the 05. Disk Brakes Australia, DBA for short and a company that has a great reputation and product, lists that they had 05 rotors. However, they didn't realize the US 05 GTO brakes were different from the 04 (I found this out by ordering a set only to find they were 04 front rotors). DBA doesn't have an expected production date yet for their 4000-series rotors (nice rotors!
steve@man-a-fre.com) but they should be out in late 2005 or early 2006. PowerSlot had said they would have 05 rotors out by the end of the 2005 summer and now say it will be closer to Christmas. PowerSlot also told me not to count on that date because the 05 GTO is lower on their priority list compared to other high-volume vehicles they need to service. iRotor.com may be another option. In a few more months, hopefully there should be some options available for a choice and some competition.
Regardless of the type of rotor, the best way to effect brake improvement is to upgrade to larger diameter rotors. Just like engines, there is no substitute for displacement. Fortunately, the 05 and later GTOs come with capable front brakes. For a significant improvement, 05 owners will have to go to 18- or 19-inch wheels and 14-inch rotor diameters. For the 04 owners, upgrading to 05 GTO OEM brakes is a cost effective solution. Unless you have 18-inch or larger wheels, its hard to better the 05 brakes. Until the aftermarket rotors appear, the solid OEM rotors are about your only choice. Fortunately, they are a very good choice.
