718 S GTS GiroDisc Rotor Install - Review

16288 Views 46 Replies 16 Participants Last post by don, 12 mo ago

don

Discussion Starter · Jul 25, 2020 (Edited)

9

Just thought I'd post my experience/review of the Girodisc Rotors for 718 S/GTS models.

Firstly, the larger GiroDisc are not any lighter than OEM but with the alloy hats the weights come out very similar so there is not really any weight penalisation. If you want to go lighter carbon ceramics seem to be the only option.

I used our regular bathroom scales so not the most accurate but you get an idea:

OEM Front 330mm Rotor 9.7kg, GiroDisc 350mm Front Rotor 10.3kg (measured ~ 353mm)

OEM Rear 299mm Rotors 5.6kg, GiroDisc 325mm Rear Rotors 5.7kg (note these measured closer to ~322mm)

As far as braking goes there might be a perceived psychological improvement but otherwise no issues and I have not noticed any fade even after 5 or 6 laps on a short track. I did have to get my workshop to adjust the rear E-brake so the hub tolerances must have been marginally different.

Asthetically I think they look nice, particularly the anodised alloy hats in contrast to the OEM Porsche rotors which always look rusty.

Here is what's in the kit including front and rear caliper spacers and longer bolts:

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Reactions: 5

21 - 40 of 47 Posts

Traum

· #21 · Nov 10, 2020

Ed @ EQT said:
Sorry for bringing this back from the dead. Aren't the stock GTS rear rotors 330mm, making the 325's a slight downgrade? Odd that they would increase the front size and decrease the rear.

You're getting your numbers mixed up, Ed:

OEM Front 330mm Rotor 9.7kg, GiroDisc 350mm Front Rotor 10.3kg (measured ~ 353mm)
OEM Rear 299mm Rotors 5.6kg, GiroDisc 325mm Rear Rotors 5.7kg (note these measured closer to ~322mm)

Reactions: 1

don

Discussion Starter · #22 · Nov 10, 2020

Just as a follow up to this Apex and Essex are recommending the Ferodo DS3.12 pad as a good option for track work with the Girodisc. I have ordered a set as my OEM pads kind of melted onto the rotor a bit so I need to clean it up and install the new pads.

The Ferodo DS3.12 pads sell for between $555 to $600us for front and rear set including discount. Not sure how that compares with OEM cost.

Ed @ EQT

· #23 · Nov 10, 2020

Traum said:
You're getting your numbers mixed up, Ed:

Ah. I think I read 229mm for rears somewhere... must have been a type-o. But the overall braking surface seems to be unchanged with the giro discs and they're a bit heavier, so I'm not sure if there's any real gain there. Possibly a little bit of extra heat capacity from the larger size if anything.

-- Ed

sobiloff

· #24 · Nov 11, 2020

@Ed @ EQT No, the fronts are 330mm and the rears are 300mm.

@don The one-use caliper bolts are why a lot of folks just get a set of caliper studs and be done with it.

don

Discussion Starter · #25 · Nov 12, 2020

sobiloff said:
@don The one-use caliper bolts are why a lot of folks just get a set of caliper studs and be done with it.

Sure I can see the caliper studs are very useful if you are regularly changing pads but for us who are changing maybe every two years or so on relatively new cars I'm not sure if it is necessary.

One brake expert thought that the one-use caliper bolts was "Porsche nonsense". Another place I read that it was more to do with the thread lock that can come on new bolts or for very old cars where they can become seized.

I've also read if you are replacing pads regularly then the removal and reinstallation of the bolts will wear the threads in the uprights, hence the studs, and/or weaken the bolts necessitating replacement, but maybe once in a blue moon is not a problem.

Ed @ EQT

· #26 · Nov 12, 2020

Well you guys got me... ended up setting up an account with giro disc and placing an order. The big issue was that I couldn’t find any other options for a slotted front rotor out there. And I’m worried that the drilled rotors won’t hold up to a more track worthy pad.

— Ed

sobiloff

· #27 · Nov 12, 2020

@Ed @ EQT I ran the DS3.12 pads for five track days with the stock rotors (Thunderhill and Laguna Seca). The days at Thunderhill saw temps over 100° F. Even with those conditions the OEM rotors held up just fine—no cracking around the holes, but they did get a bit worn.

Regardless, the Girodisc are a better long-term investment—enjoy yours!

Reactions: 1

sobiloff

· #28 · Nov 12, 2020

don said:
Sure I can see the caliper studs are very useful if you are regularly changing pads but for us who are changing maybe every two years or so on relatively new cars I'm not sure if it is necessary.

One brake expert thought that the one-use caliper bolts was "Porsche nonsense". Another place I read that it was more to do with the thread lock that can come on new bolts or for very old cars where they can become seized.

I've also read if you are replacing pads regularly then the removal and reinstallation of the bolts will wear the threads in the uprights, hence the studs, and/or weaken the bolts necessitating replacement, but maybe once in a blue moon is not a problem.

I've done enough work with aluminum to be very wary of steel bolts threading into aluminum, like Porsche's steel caliper bolts threading into the aluminum uprights. If I can put studs in uprights once, and be done with it for the likely life of the car, I'm all-in. But, as you point out, YMMV!

Reactions: 1

don

Discussion Starter · #29 · Nov 13, 2020 (Edited)

Well the indpenedent Porsche workshop that I use said they want to replace the bolts so looks like I will cave to the peer pressure

I am just decided whether I just get new bolts or pay the $212 for the stud kit.

Actually he did make one other good point regarding the heat cycles involved with track use can also cause the bolt to fatigue so that could certainly be another reason to replace the bolts if you are tracking the car, rather than only driving on the street.

Ed @ EQT

· #30 · Nov 25, 2020

So far so good with my Girodisc’s and DS3.12’s. First track test coming up on Saturday!

— Ed

subawang

· #31 · Nov 25, 2020

Did anyone happen to measure the thickness of the Girodisc front rotor? Wondering if they capitalizing on the thicker rotors possible with the 718 S calipers.

don

Discussion Starter · #32 · Dec 4, 2020

subawang said:
Did anyone happen to measure the thickness of the Girodisc front rotor? Wondering if they capitalizing on the thicker rotors possible with the 718 S calipers.

I think they are the same thickness as OEM. Mine measured ~ 34mm front and 20mm rear which is same as OEM, maybe a little thicker when new ~ 1mm.

don

Discussion Starter · #33 · Dec 4, 2020

Just to update, I had to get my Girodiscs machined as they warped. I don't think it was particularly a fault with the rotors but probably just a relatively hot track session and not enough cool down as the particular track where they warped is very short ~ 1'10s laps. Maybe also something to do with the OEM pads, not sure.

So note to self to make sure I cool down the rotors on hot days with an extra lap or so. I've had them machined and they feel as good as new now with Ferodo DS3.12 pads so I'll see how they go with extra cool down.

For some reason the rears also ate out the shoe bakes/pads on my electronic park brake but that might have been poor adjustment by the mechanic as they were initially playing up after fitment.

b-grif

· #34 · Dec 10, 2020

don said:
Just to update, I had to get my Girodiscs machined as they warped. I don't think it was particularly a fault with the rotors but probably just a relatively hot track session and not enough cool down as the particular track where they warped is very short ~ 1'10s laps. Maybe also something to do with the OEM pads, not sure.

So note to self to make sure I cool down the rotors on hot days with an extra lap or so. I've had them machined and they feel as good as new now with Ferodo DS3.12 pads so I'll see how they go with extra cool down.

For some reason the rears also ate out the shoe bakes/pads on my electronic park brake but that might have been poor adjustment by the mechanic as they were initially playing up after fitment.

Good to know. I was wondering how long these rotors lasted and if they had cooling issues. Looking forward to more updates!

Reactions: 1

InigoMontoya

· #35 · Dec 28, 2021

don said:
Maybe the larger Girodisc rotor gives the brakes slightly better feel over stock. It means there can be a little less pad/brake pressure to achieve the same braking force but maybe the noticeable benefit is more psychological. I think the floating rotor design on the Girodisc (rather than the fixed OEM) can also help with brake feel under some situations.

The Porsche 6 piston calipers also require a larger Master Cylinder so you are looking at unnecesary extra cost IMO for most purposes. I think even the GiroDisc upgrade for most people is not necessary but if you need to replace your rotors anyway then it is a nice upgrade. If you were doing a very long race, maybe 1 hour or more I think the larger 6 piston caliper and rotors become more important, otherwise the GiroDisc seems plenty good enough for many track drivers.

The braking surface on the GiroDisc is the same size as the OEM rotor so the pads do engage the full width of the braking surface. You can see the bedding in on the full width of the rotor surface in the photo below. I think if you compare this to the bedding on the OEM rotor above, maybe the coverage of the GiroDisc is a little better/more precise.

My OEM pads were still in good condition so I kept them but sure a lot of people upgrade pads with the rotors. However, if your pads are still good you can have your workshop burnish the pads and bed them in as per usual. I don't think there is any disadvantage, but as noted above some people say you should not reuse the caliper bolts too often if you are changing pads regularly, which in any case you should also get the caliper stud kit.

Sir, are you sure, that a larger master cylinder is required for 6 piston upgrade on 718? Suncoast sells a two 6 piston upgrade kits for Base cayman and Cayman S and they say nothing else is required. They sell a 340mm 6 piston kit from 911 and a 6 piston 350mm compound rotor kit from the Cayman GTS 4.0. I have tried to search for master cylinder part number for both the base and 4.0 with larger brakes and but I can only find the one for the base. Is the 4.0 MC larger? I know in the 981 you could upgrade the master cylinder for the the carbon brake unit but when I look up master cylinders I see one for GT4, Spyder which have different brakes than the Cayman Base, T, S and GTS. If you don't know, does anyone know if the master cylinder on the 2021-2022 Cayman GTS 4.0 with 6 piston calipers is bigger?

don

Discussion Starter · #36 · Dec 28, 2021

InigoMontoya said:
Sir, are you sure, that a larger master cylinder is required for 6 piston upgrade on 718? Suncoast sells a two 6 piston upgrade kits for Base cayman and Cayman S and they say nothing else is required. They sell a 340mm 6 piston kit from 911 and a 6 piston 350mm compound rotor kit from the Cayman GTS 4.0. I have tried to search for master cylinder part number for both the base and 4.0 with larger brakes and but I can only find the one for the base. Is the 4.0 MC larger? I know in the 981 you could upgrade the master cylinder for the the carbon brake unit but when I look up master cylinders I see one for GT4, Spyder which have different brakes than the Cayman Base, T, S and GTS. If you don't know, does anyone know if the master cylinder on the 2021-2022 Cayman GTS 4.0 with 6 piston calipers is bigger?

I'd check with Suncoast about whether or not it is necessary but the posts on renlist have upgraded the MC. Also for others, note that the Girodisc upgrade for the 718 4 piston calipers is different from the 6 piston 4.0/991/992 upgrade so worth considering the 6 piston caliper upgrade as well at the same time.

Here are the part numbers for the MC:

Master Cylinder

99135513027 or 99135513028 Master Cylinder x 1

99135501302 Expansion tank x 1

WHT005308 Outer hexagon round screw M 5 X 51

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InigoMontoya

· #37 · Dec 29, 2021 (Edited)

don said:
I'd check with Suncoast about whether or not it is necessary but the posts on renlist have upgraded the MC. Also for others, note that the Girodisc upgrade for the 718 4 piston calipers is different from the 6 piston 4.0/991/992 upgrade so worth considering the 6 piston caliper upgrade as well at the same time.

Here are the part numbers for the MC:

Master Cylinder
99135513027 or 99135513028 Master Cylinder x 1
99135501302 Expansion tank x 1
WHT005308 Outer hexagon round screw M 5 X 51

Thank you. Are these numbers for the Cayman 4.0 GTS or Base/T/S Variant? I googled them and they show they are for 911 not Cayman from what I found.

don

Discussion Starter · #38 · Dec 29, 2021

That's right the master cylinder upgrade is not an option for for the 718 so there is no specific part number for that model, only for the 911 or 981 Spyder. Not sure about the 4.0.

Note with the larger 6 piston caliper and larger rear caliper and larger/thicker rotors you are adding unsprung weight so from a performance point of view the standard 4 piston calipers are more than adequate for most purposes, particularly with race brake fluid and pad upgrade. Otherwise I'd go the 6 piston and larger rotors for heavier/longer track sessions where brake performance will give you the fraction of seconds for a PB. Otherwise through mountain roads and shorter track sessions I think the standard brake set is adequate and possibly better from a weight perspective.

InigoMontoya

· #39 · Dec 30, 2021

don said:
That's right the master cylinder upgrade is not an option for for the 718 so there is no specific part number for that model, only for the 911 or 981 Spyder. Not sure about the 4.0.

Note with the larger 6 piston caliper and larger rear caliper and larger/thicker rotors you are adding unsprung weight so from a performance point of view the standard 4 piston calipers are more than adequate for most purposes, particularly with race brake fluid and pad upgrade. Otherwise I'd go the 6 piston and larger rotors for heavier/longer track sessions where brake performance will give you the fraction of seconds for a PB. Otherwise through mountain roads and shorter track sessions I think the standard brake set is adequate and possibly better from a weight perspective.

Yes, I take the weight seriously especially with a Cayman T. The Cayman GTS 4.0 350 fronts are a compound disk with aluminum hat so was hoping that would reduce weight a bit to minimize weight gain. I think the 4.0 with the bigger brakes has the same MC and the Spyder and GT4 have a different one but I have asked Suncoast for an answer. Thank you.

MikeDe

· #40 · Feb 25, 2022

Random question: Do these giro disc rotors rust up quickly like the stock rotors do when washing the vehicle?

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