Jbgill6535

I thought I found this once before and subscribed, but I can't seem to find it anymore.
Has anyone converted the OEM rotors on a 991 GTS with Centerlocks to Girodiscs? I am also upgrading to Tarret caliper studs and interested to see if anyone has already done this and has any feedback on issues.

TIA
Jason

RobC4sX51

I could be wrong (most likely) but I thought I read on the GD website that their brake rotors were not compatible w CL wheels nor PCCBs.

Jbgill6535

Thought that as well, but Clark at Apex and a rep from Gdisc disagreed. We will know by this weekend.

Vise

I'm interested in hearing what you find out, I have CL's as well and have been looking at the Girodisc rotors as a replacement for OEM (which will hopefully last until next year).

iamksharp

Any update here re centerlocks and giro?

cajerseyboy

Following.

Jbgill6535

Sorry for the delay. We are caught up in new house buying and moving!

First I want to give kudos to Clark at Apex Performance for the great job in getting all the components correct for me. I was looking for an upgrade that could handle track and street use. I did all the work myself using my quick jack in the garage and I am no professional mechanic.
The background on the car is that I bought this 16 GTS with center locks in June with 6k miles. I have done a couple week long drives at the Tail of the Dragon and 3 or 4 PCA/NASA HPDE weekends in the yellow group. After 12k miles, the rotors were splitting around the crossed drilled holes and were almost touching the edges of the rotor. At the last DE pads went from 60%to 20% in one session and the rear pads were significantly more worn than the fronts, due to what I presume is the work of PTV.

For the rotors, I ordered the Girodisc A1-032S L/R 350mm slotted rotors, 10mm diameter greater than stock, which also fit the 996/997 turbos instead of the 991 A1-122S L/R rotors in order to be able to use larger pads, which are not available for the 991. If you are content to use PORSCHE 991 Oem pads, the the 122S rotors would work. For track application I am using the pads recommended by Clark, Ferodo FCCP4664W up front. Although both of the available rotors are 350mm, the 032S utilizes a smaller diameter aluminum rotor hat, which accommodates the larger sized pads.

In the rear, the rotors are the A2-032S L/R 350mm slotted from the 996-997 turbos, which gives a 20mm diameter increase from stock. As Ferodo does not have a pad that will work with this size rotor, Clark recommended the Pagid yellow RSL29 S4909.

To accommodate the larger rotors and to allow for frequent pad swapping from street to track, I contacted Ira at Tarett and purchased the 92mm studs. On the front, the studs fit as required without the use of spacers, however in the rear, I had to utilize the 12mm spacers provided by Girodisc with the rotors. Good insurance to prevent stripping of the aluminum wheel carriers with the caliper bolts

After installation and bedding, I found that the upgrade provided a significant increase in braking ability, the downside being that the setup is entirely too noisy for street use, as expected.

So, at the risk of getting flamed for not using Oem parts, I used Centric, owners of Stoptech brakes, pads for the GTS, item #s 10416640 front, 1041470 rear, from Rockauto for about $100 bucks for all four corners. As a point of reference, I think OEM pads can be purchased online for around $400. I didn't feel that brake pad sensors were really a necessity but I also found centric 2 wire sensors, item # 11637047 for $13 bucks and the Pagid 1 wire sensor for $8. Again, OEM 1 wire sensors can be purchased for $68 apiece.

Very happy with the upgrade and would definitely do it again. Hope this helps. Let me know if you have any questions

Jason

Jbgill6535

Pics wouldn't load in last post.

Jbgill6535

Pics of tarett 92 mm caliper studs, 12 pt. nuts and Girodisc spacers

Brian E

Jason how do you like the Quick Jack? Any issues using it on your 991? Did you buy the 5000, or 7000? I was all set to pull the trigger on the 5000 last summer, but I spoke to Jeff at Q.J. and he said they were making some revisions to the hydraulics, so I held off placing my order. Any feedback would be appreciate as I would like to get one on order.

Thanks
Brian

cajerseyboy

Thanks for posting Jason! Very helpful. I have a few follow up questions in red below as I'm going through the buying process.

Thanks again for the help, Jason. Nice GTS BTW

Jbgill6535

Brian,

They are a great tool if you don't require extreme heights. Didn't have very good luck initially. I bought the 5000 in June and had numerous problems which required the return of 2 motor units. The third one has worked without issue. I found quickjack's customer service to be very responsive with the issues. In the end they qc'd a complete new unit at their facility and sent out a fully functioning setup. It is easy to store, setup and provides more than adequate clearance for most tasks that I am interested in tackling on my own. For the price and what it provides, there appears to be no other option.

iamksharp

Thanks for the quick update!! So for girodisc since the rotors are bigger a spacer and a longer bolt is needed? These are items that any reputable track car shop should have right? Thanks again!!

Jbgill6535

Thanks. Looks like we have similar tastes.

I chose the Ferodo over Pagid based on recommendations from a Clark regarding performance and longevity and would have gone with their rear pads if they were available for this application. After bedding I did notice that the Pagids were significantly more noisy. Not an issue if you are using for track application, but still very noticeable.

The 12mm spacers come from Girodisc along with a new set of caliper bolts if you decide to go that route. In the pictures, it is the gold ring seated against the caliper.

As for the part number on the studs, thanks for making me go back to check, as they are actually 95mm long. They are part number BCSK 95. For the rear studs, you will also need the Girodisc Adapter sleeve, part #GDASBCS-95. The sleeves slide over the caliper stud before you install the caliper to center the caliper and eliminate any play.

Not sure of the issue with the Centric brake pads on Rockauto. Pic include of the invoice.

Let me know if you need anything else.

Jbgill6535

Correct. Since the rotors are larger in diameter than stock, they will require a longer caliper bolt and spacer, which are included with the Girodisc rotors. If you frequently change pads for track/street, many recommend the safety of a caliper stud. These prevent accidentally stripping the threads on the wheel carrier, which can be a costly repair. Porsche recommends new caliper bolts each time they are removed. These are available from Tarett are detailed above. I'm not sure about other track shops though.

Hope that clears things up.