The front rotors appear to be 2 piece with a distinctive hat. The rear brakes are definitely 1 piece.

Anyone confirm the design of the front brake rotors, 1 or 2 piece?

 

They are 1 piece.

 

on a GTS the fronts are 2 piece duel cast. The hat is separate from the iron disk and separated/ connected by pins. Unlike some of the aftermarket 2 piece rotors you can not just replace the disk because it is pinned and not bolted together. The rear rotors are a 1 piece design.

 

Thanks for the response. So it would seem the fixed stock 991.2 GTS front rotors provide the benefits of a 2-piece GIRO Disc style rotor, mitigating heat transfer from the rotor, eventually to the caliper: Nice touch. While looking at the front rotor, I saw those pins that connect the hat and the rotor and couldn't imagine how they could be separated. They can't.

When it comes time to replace my front rotors, I am going with GIRO Disc, get them from Clark at APEX Performance. May do the rears too. If I am going to have to pay over $1,000 for a set of front rotors, might as well get 2 piece where I can save a few bucks next time.

 

Yes, they also allow float during thermal expansion. I have heard various opinions on weather studs or bolts are a better design though most of the aftermarket stuff is bolted.

 

The dual-cast discs are nicer than traditional one-piece, but they don't have the airflow or weight savings of a true 2-piece disc. They also have drill holes, which are prone to cracking.

Please consider our AP Racing J Hook 2-piece Discs when it's time to replace yours. Clark at APEX carries them as well. We have many satisfied customers within the Porsche community and elsewhere, and AP Racing is the world leader in brake technology. You can see our discs for the 991.2 GTS here, along with our other brake products: https://www.essexparts.com/my-vehicl...TS/Iron%20disc

Thank you for your consideration.

 

I will look into Essex, thanks for the "heads up".

 

The GiroDisc, whether front of rear, are true 2 piece rotors, hats and rotors, lighter than OEM. Another feature, they are rebuildable, you reuse the hats and buy replacement rotors when the time comes, as it always does. Below data I posted a while ago, all you need to know:

From GiroDisc: “The GiroDisc system is a direct replacement for the OE discs, no modifications are necessary. The disc will bolt directly to the car and work with OE calipers perfectly. By upgrading your brakes with lightweight high-performance replacements as opposed to a big brake kit, your factory bias is maintained as well as your ABS efficiency. (Also note Big Racing Calipers are heavier than stock).

Once the GiroDisc system is in place, simply replace the cast iron (Outer) rotor when needed. Some discs are larger in diameter and come with caliper spacers. If longer bolts are required, they are also supplied. The innovative two-piece design is lighter than conventional steel rotors, can save 4-8 pounds of weight (For a set of 4) compared to the factory rotors.

The central hat section of our rotor is made from strictly U.S. sourced 6061-T6 aircraft specification aluminum. The disc is made from our own proprietary cast iron, poured in the USA and machined from start to finish in house at GiroDisc. The rotor utilizes a curved vane design, developed in racing to act as a centrifugal pump to force cooling air through the disc.

The rotor and hat have a floating mount system, which utilizes 10 high strength alloy steel drive pins, manufactured by GiroDisc in the USA to our own specifications and cadmium plated for a long-lasting corrosion resistance. These pins take the load from braking actions while maintaining the axial and radial float between the hat and disc. The pins are secured by class 12.9 cap screws with hardened washers. In order to keep the rotors from making noise when cold, the pins are mounted with anti-noise spring washers on the rotor side which allow the rotor to grow with heat expansion but eliminate the rattle and noise associated with floating rotors. This float also allows the rotor to self-center between the pads.

Once the GiroDisc system is in place, simply replace the (Outer) cast iron rotor when needed. Some discs are larger in diameter and come with caliper spacers. If longer bolts are required, they are also supplied. The innovative two-piece design is lighter than conventional steel rotors, can save 4-8 pounds of weight compared to the factory rotors.”

My stock 991.2 GTS 350 mm in diameter front rotors were approaching their wear limits, time for replacement. I checked on-line with Gaudin Porsche in. Las Vegas. They quoted me $572.74 for a pair of new OEM front rotors, and $15.00 for the 4 caliper bolts, for a total of about $600. That is pretty cheap compared to other OEM sources I have checked into. I know I also could have gone to a non-OEM source, maybe even cheaper.

There are things I don't like about the OEM stock rotors: They are "drilled", to lighten them. In the past I have had the holes in my "drilled" rotors fill up with brake dust. Maybe that's not a big deal, but I don't like it when holes appear clogged. Also, in the past, admittedly after hard usage, cracks could start forming in the rotors. If a crack should "grow", connecting 2 "drilled" holes, the rotor(s) must be replaced, irrespective that the thickness of the rotor possibly being within Porsche specs.

I also feel that the OEM rotors are a bit heavy, relative to a 4-wheel set of GiroDisc 2-piece rotors, saving 4 to 8 lbs., based on one’s Porsche model (Confirmed by my research). The obvious question, to receive the benefits mentioned below, would I be willing to pay almost 2.2 X more $600 at Gaudin Porsche VS $1,300 from GiroDisc? I rationalized that the benefits seen below, are worth it being that I would receive:

• Reduced un-sprung weight for the rotors, 4 to 8 lbs. for all four compared to OEM (See attached EXCEL FILE for 991.2 GTS specifics.)
• Better heat dissipation, reducing the risk of brake fade,
• Lower risk of rotors warping (They runner cooler than OEM)
• Better cooling with enhanced air flow exposure,
• No drilled holes to clog up with brake dust,
• Rotors and hats are separate, when the rotors wear out, no need to replace the hat, buy the rotors separately, for about $800 a set, front or rear, just a bit more than replacing 1-piece OEM motors.
• The rotors are inscribed with curved cooling vanes. When the vanes are worn clean, it’s time to replace the rotors. I have found that measuring stock rotor thickness, without removing the wheel, is inconvenient at best, and more so if one has center lock wheels.

Bottom line, I was ripe for a conversion to GiroDisc 2-piece rotors compared to OEM stock. I just installed the fronts. Got them from Clark at: chamerly@apexperformance.net. The brakes have a better feel for me. He doesn’t charge sales tax and Apex Performance stocks all sorts of brake pads to match your usage reequipments. In the near future I plan on upgrading the rears. Also, for my car, the rear GiroDisc rotors 350 mm, compared to OEM at 330 mm, will be the same size as the fronts.

In conclusion, I am not connected with GiroDisc or Apex Performance in any way. I have had a long love affair with GiroDisc, and Apex Performance for that matter. Also note, prices for GiroDisc rotors have remained nearly static for many years.