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Discussion Starter · #1 ·
Sorry if this subject has been discussed repeatedly, but I have trouble finding current info on the subject. Also, I am not well versed in the subject of braking. I have a 2014 981S. Many people say the 981 brakes are great, but there have been numerous times when I would have preferred a little better brake feel and stopping power. I have stock rotors, but have upgraded to Endless MX72 brake pads (expensive, but a great improvement), and Brembo HTC64 brake fluid.

I am in the process of changing to the gt3 master cylinder and braided ss brakelines. From prior discussions, this seems to be a good upgrade. I still have 6+ months before I change the rotors, but I would like some advice.

The stock rotors are 330x28 & 325x20. The Girodisc rotors are 350x28 & 325x20 (taller but not wider). I heard they are lighter and the two-piece design will help on the future replacement costs. Obviously, your pad size stays the same, so the advantage here is the greater mass to help deal with the heat, quality engineering, and no cross drilled holes to encourage the cracks due to heat variations. I see that the kit comes with spacers and longer bolts. Is that how they get around the clearance issue?

Will I feel any improvement in the brake feel with an upgrade to Girodisc, or will it be just longevity? I see the price on the full set of Girodisc to be around $2140.

I have seen references to Pagid RBD rotors for $3500, but I think they only have sizing for gt4 club sport, 997 and 991. It looks like Brembo does not offer the correct size as well. So is Girodisc the best option?

Any thoughts on the 6 piston front brake conversion offered on Suncoast for $1995? Does the mc adjust for front-rear bias?

Any thoughts on adding the gt3 brake ducts?
 

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I have no knowledge of the Girodisc rotors, but I can confirm the GT3 brake ducts help greatly with cooling down the front brakes. In the past couple of years, I have picked up the track bug and decided to join the local race track country club. In the process I also picked up a 2016 Cayman S to use exclusively on track. Before taking the car to the track for the first time, I changed out the stock pads to RE-10s, added SS lines and flushed with Brembo HTC64 fluid as well. Since Tuesday is my normal track day, it is normally pretty empty and I end up being the only one on the track for an entire morning somedays. This means that I can stay out on track for 30-40 minutes without stopping and it takes a toll on the brakes. Between 25 to 30 minutes, I start to feel the brake pedal softening up and by 35 minutes I would have to give the pedal a quick tap before actually braking. This slowed down my lap times for the rest of the session since I had to take it easier on the brakes, so I started looking at different solutions.

At first I was thinking about the Girodisc route with some titanium shims, but since I plan on building this car up to be a more serious track car, I decided to spring for a full set of Brembo GT brakes. I have been using a set of 18" OZ wheels with RE-71R tires, so after consulting with Race Technologies, we decided that the 6-piston 355x32 fronts and 4-piston 345x28 rears with some RE-10 pads would be the way to go. Since the fronts were on back order, I have not had a chance to test them out. In the meantime, I also had the GT3 ducts and 911S master cylinder installed. With the better cooling from the GT3 ducts, I will be on my third 30 minute session of the day before the brakes are noticeably softer and the master cylinder provides a firmer pedal from the beginning. I would double check with your shop to see if the GT3 master cylinder will actually fit because my independent shop claimed that I could only get the one from the 911S which has a slightly bigger piston. It may have something to do with the fact that I have PTV, but I am not 100% sure.

The Brembos will be shipped this week and hopefully I can squeeze in an additional track day with them on 10/31 before the season ends here in Chicago. In the end if you are not tracking your car and want better brake feel and stopping power, I would suggest that you just get the upgraded master cylinder (whatever version that maybe) and SS lines. Unless you are on the brakes really hard all the time, you really don't need the better cooling from the GT3 ducts, bigger Girodisc rotors or better brake systems.
 
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it really depends on the usage and what kind of load you put on your brakes.

for me - front and rear cooling solved fading completely.
master cylinder gave shorter and harder pedal - i love it.

i'v put front PFC rotors - but i suspect i didn't really needed them.

Girodisc sound great, but replacement costs are not cheap.

if you want pure better stopping - you know tires are responsible for that.

better bite - yes, bigger rotors (diameter), bigger pads (bigger caliper) is the way.

better heat capacity - larger rotors+pads/caliper.
but for this cooling is #1 - it costs less than 100$ and if you didn't do it yet - don't spend thousands on hardware.

better fluid is absolutely the first thing to do - but you already did this which is great.

BTW - i'm also on Endless mx72 - i'm addicted.
 

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I was tired of the thermal cracks from the OEM drilled rotors but I've changed my mind. The drilled rotors are about $100 - $150, so that's not expensive. Now I look at the thermal cracks to tell me how badly I've beaten up the rotor. I don't think slotted rotors would "give" me that information.
 

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I was tired of the thermal cracks from the OEM drilled rotors but I've changed my mind. The drilled rotors are about $100 - $150, so that's not expensive. Now I look at the thermal cracks to tell me how badly I've beaten up the rotor. I don't think slotted rotors would "give" me that information.
That's an interesting view. I was about to get slotted rotors to avoid the cracking you see in drilled rotors... is it actually a good way of seeing if the rotors need replacing or is it just a feature of drilled rotors to crack?
 

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There are front and rear GT3 Brake ducts. In the front, you can go to 991 GT3 or GT4 front fender liners and a duct that comes off them. This is in addition to the duct on the lower control arm. The fender liners have a much larger opening for air flow through the radiators into the wheel well and the duct (scoop) then pushes the air against the caliper and rotors.

Note that both GT3 and GT4 fender liners need to be modified to fit. The GT3 part has a nose that fits from the fender liner to the front splitter. It is too long and needs to be shorteded, but all the stock holes line up. The GT4 fenderliner needs the outside edge trimmed off and two holes moved to fit properly. I am assuming the GT4 bumper cover is a bit wider and the piece was widened to fit. The good news is the length is correct. My modification thread has photos of both the GT3 and GT4 fenderliner noses as well as on an older page, the part numbers for the rear GT3 air ducts.

On the rear, if you have an S or later, you already have the one duct that attaches to the leading edge of the lower control arm (it can be added for a base car). I found that the 997 GT3 rear L-shaped air ducts are a good fit, but only if you have a larger than stock rotor. They are designed to blow air at the outer edge of the rotor and were designed for a 350mm or larger rotor. The 991 versions are different and expect a 380mm rotor. GT4 has a different LCA and they don't fit, but they come with a similar duct that work the same way.

In my case, I have Brembo GT brakes with Type III slotted rotors, Pagid RS29 pads all around and the GT3 air ducts front and rear. I have never had an overheat issue with the front brakes and the rear overheat issue was cured with the GT3 rear L-shaped ducts. Recently, I upgraded to the Tarret Cup design monoball-based LCAs all around and the three sided bracket that holds the rear L-shaped air ducts to the LCAs does not fit, but I can modify the bracket and it should fit (the LCAs are just a bit wider than stock). Running recently at Mid-Ohio without the rear GT3 ducts, I suffered rear brake fade due to overheat and had to limit my top speed at the end of the back straight. The ducts will be on there next track season.

V6
 

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Discussion Starter · #8 ·
Thanks for the responses. I got the same answer I often give to others - "it depends what you want to do with the car". The usage is approx 25% track and 75% canyon (I should get in 10 HPDE days and 20 canyon runs this year, plus the mileage to and from), and I rarely use it around the city. I know I should do one mod at a time, run the car for a while, then tweak or add another. But I do not do my own mods, so that is not always practical. I have a 981S with JRZ RS1 coilovers, Bbi toe link, Bbi toe steer, Bbi thrust arm, and Tarrett sway bar endlinks. Endless pads & Brembo fluid. My latest changes are in process - wider HRE forged lightweight wheels, gt4 size MSC2 295 & 245, gt3 master cylinder, braided ss lines. The rotors, calipers & duct work are stock.
The canyons rarely need great brakes, unless there is a problem in the road. But the brakes are not used enough to get too hot.
The track is different. The car has never failed me, and I have never failed the car, but there have been a few moments coming off of a straight at 130 and slowing down to 60 to make the turn that were concerning. Towards the later part of a hot day, I feel the car becoming less reliable in the tires and brakes. That is when I shut it down and pack up.
A big Brembo brake kit is overkill for me. But bigger and better rotors, like Girodisc, that are stronger and last longer probably make sense. And longer lasting rotors will save me some labor costs with the less frequent replacements.
All the research I did concluded the same thing, ferrari, porsche and other high end sports cars used cross drilled in the past due to inferior brake pad materials releasing a gas. Now brake pads are much better, but the cross drilled remain because it looks good. argggh.
 

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I have a 981 Cayman S which I use similar to you.

I installed the Girodisc rotors front and back with Pagid yellow front pads, Pagid black rear pads and titanium shims all around. I have since tracked the car at both Road Atlanta and VIR with CHIN Track Days. I run in the blue group where the pace is quick. The braking performance is excellent. Great stopping power and no fade. I would highly recommend this set up.

Good luck!
 

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These were the GT3 brake cooling part numbers that were ordered for my car. The wheel housing with grille routing holes line up, and the air guide required only slight modification to work.

991.575.132.01
991.575.131.01

991.504.501.94
991.504.502.94

What are the GT3 ducts? If they cool the brakes, then I really, really need them!
 

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I was tired of the thermal cracks from the OEM drilled rotors but I've changed my mind. The drilled rotors are about $100 - $150, so that's not expensive. Now I look at the thermal cracks to tell me how badly I've beaten up the rotor. I don't think slotted rotors would "give" me that information.
You can get very inexpensive slotted rotors from Pelican Parts. And I think the best indicator of rotor wear is its thickness as opposed to the amount of cracking. The way I see it, no amount of cracking in the rotor is normal, since it means the strength of the metal is compromised. But I am not an expert! :)
 

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That's an interesting view. I was about to get slotted rotors to avoid the cracking you see in drilled rotors... is it actually a good way of seeing if the rotors need replacing or is it just a feature of drilled rotors to crack?
i haven't seen yet drilled rotors that didn't crack.
i don't get why manufacturers put them on the sports cars.....

plain rotors are the best IMO. hard to get them for Porsche.
slotted Sebros are fine.
 
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Regular brakes can come off the track with rotors still at 450-475 degrees in the front as measured on a fluke infrared gun. My upgraded PCCB 6 piston front calipers; with giro disc 350x34 rotors; and better cooling with GT3 ducts on the LCAs as well as GT3 ducts on the inner wheel well and also half of the vertical plastic fins cut out of the radiator fan vent ducting in front of the wheel equalled 325 degrees on the infrared gun. Same Cayman S, similar drivers in the highest PCA classification, with testing done within a minute of each other right after coming off the track. So larger thicker calipers and rotors with much better cooling can make a big difference to the tune of about 125 degrees even after coming off the track. This would likely be more in the range of 150-200 degrees while actually driving and doing the braking.
 

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These are the part numbers for the inner wheel well air deflectors. They send the air to the center of the brake rotor. About $70 each and a simple install with a little home make bracket made of aluminum. These will dump a lot more air onto the brakes.

Air Deflectors - 99157513181 and 99157513281

Auto part Tire Brake Vehicle brake Fender
Auto part Tire Brake Automotive tire Automotive exterior
 

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Not available anywhere in Europe, go figure. Been searching for slotted rears for days now, there is _nothing_ other than the very expensive Giros. Plenty of cheap drilled solutions though. People think they look "cool" I guess?
i just ordered from Pelican and shipped overseas.
i thought Sebros are made in Eu - are they not????
 
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