So can anyone confirm for sure that the base and S rear calipers are identical for the 991.2 regardless of color?

The base to S brake upgrade is a lot more attractive when you don't have to buy rear calipers and can just swap rear rotors and pads.

Because of “centrifugal force” (is that the right term?) that may be placed on the caliper studs. I’m a bit obsessive compulsive and, even if they spacers are most likely fine, didn’t want to use them where unnecessary on front. I may rethink my position for the rears, but at the same time, most of the braking is done up front and sticking with Sebro slotted rotors for the rear may be more cost effective over the long run.

Why switch to studs instead of using the included longer bolts at the rear calipers?

My car is in today to get the Girodisc rotors + Ferodo DS2500 pads installed, should hopefully get it back tonight or tomorrow at which point I can report back on initial thoughts from the street. Next track day isn't until early August though.

Because bolts present the risk of stripping the threads in the aluminum carrier. Studs are installed once (albeit replaced on a schedule) and a nut is used to secure the caliper. Same for wheel studs. I use wheel studs and caliper studs to avoid the risk of stripping the threads.

Just a few comments and pictures that may help others considering GiroDisc. I have the GiroDisc and Tarett stud kit for the front and rears. Like others have said you do not need the caliper spacer for the front GiroDisc if you get the right part number. Note, when I called Tarett and asked what stud length to order for a 991.1 they told me what length to buy for the front and rears and what they told me for the front was wrong. The front studs were too long and I could't get the caliper clamp load. Make sure you are checking this! A few calls and emails later and they shipped me the correct length front studs. Note, Tarett also said the rear stud kit would need the stud sleeves but the front would not need the sleeves. All I have to say is get the sleeves for the front and rear studs. It's a much better fit. I think their logic was the shoulder on the front studs is enough to center the caliper the same as the factory bolts. In my opinion there isn't enough shoulder so get the stud sleeves. I put a little RTV on the inner diameter of the sleeves and spacers and it helps hold them on the studs so they don't slide off. On the rear kit, it does require the 12 mm spacer. (red) Look closely at the picture of the rear caliper and contact area with the aluminum arm. Without spacers you can see the contact area for the two caliper bolts on the rear. Yes, it's an unusual shape of contact that is simply changed to the perfectly circular contact area of the red spacer. Arguably there is a small reduction in contact area but plenty to maintain the joint stiffness when bolted up. And Tarett sure should have done the analysis and measurements to show their parts are ok. If you track your car just check the contact area and look for aggressive wear or fretting. Just make sure it's torqued correctly. I also installed the brake line stud kit and that helps get a little more freedom to move the caliper around when changing the pads. I run PAGID's for the track and they work fine. Lastly, I saw the one person comment about the pad size and contact with the rotor. If you just installed a new pad on a new rotor from what I've seen it takes a while for there to be enough wear to see the real contact area. These pads are not flat and the rotors aren't perfect either. They have to wear in to see the full contact area. The picture I saw looked like the parts where still wearing in and the width of marks was not where it would be after wear in.

Anyhow, I hope it helps. I've got tons of pictures on my install if anyone needs them.https://cimg0.ibsrv.net/gimg/rennlis...aee9ec3de8.jpg

Rear caliper stud and sleeve...you can see the factory contact area with the caliper prior to installing the red spacers.
https://cimg4.ibsrv.net/gimg/rennlis...55237ef4b4.jpg

Rear caliper with the Tarett stud kit, sleeves, and spacers installed.
https://cimg2.ibsrv.net/gimg/rennlis...ab9aeb18f2.jpg

Rear caliper with the Tarett stud kit, sleeves, and spacers installed.
https://cimg4.ibsrv.net/gimg/rennlis...c29357f4a2.jpg

Rear
https://cimg5.ibsrv.net/gimg/rennlis...81da3e90e8.jpg

Front

Got the car back tonight and only went for a quick spin around the block to check it out... first impressions are very positive, the brakes are very strong and zero noise so far. Remains to be seen how things work on the track including wear but I'm very pleased with initial impressions.

This is what I was looking for!:rockon:

Thanks for the awesome write up. You don't happen to have the stud lengths handy to pass on? (or I guess I could just call Ira he's usually pretty good about remembering details for specific installs)

This is Rennlist at its best.:cheers:

Vise: looking forward to your report as well. If you bedded the new pads in properly you probably won't get any squeal for a few miles (if they are going to squeal at all).

Thanks again guys!

Rich

In addition to this it also makes changing brake pads a lot easier especially when you're in the middle of a track day.

https://cimg4.ibsrv.net/gimg/rennlis...4e6afc1e14.jpg

For my 2012 991.1 it used the 95 mm studs in the rear and 77-85 mm studs in the front. I've attached the picture Ira sent me that is how he figured out what stud length to ship after I ran into the problem. You can see in the picture the 95 mm stud on the left had to have 3 washer to get clamp load since it ran out of threads. For the 77-85 mm studs (that's what it shows on their website) you can use 1 washer and you have plenty of thread to ensure a clamp load. I never understood why Ira's recommendation didn't work but the shorter stud with the sleeves is what worked perfectly. Ira shipped me the correct length and all was fine after that. It wasn't fun removing the loctited stud after it was installed! And, with that longer stud, it was tougher to lift the caliper up and over the studs so the brake pad changes are much better with the proper length. So, double check with Tarett but for my 991.1 this is what worked for me.

Cheers!

Couple days of around town driving and I'm still very impressed with the new setup, feels much more stable + strong than the stock setup although that was likely a factor of my rear rotors being toast. Did some hard braking exercises earlier and it is a noticeable improvement so I'm very pleased so far. We shall see how the DS2500s where after a couple days of track use/abuse at Calabogie in August though.

Going to do two days at Sebring in September so after this event the car will need new pads and the rotors have a lip on them so they will be toast too. /\ /\This is the next upgrade...great info.