ERinEC

Time to replace the rear rotors on my 991.2 C2S. It appears that Sebro does not offer a slotted rotor for my car. Will the cross drilled ones hold up for two or three track events a season? Or am I better off going with OEM? Not looking to spend $1300 on Girodisc. Thanks!

G.I.G.

I think OEM rotors (Sebro or Zimmermann) are probably fine for 2-3 track days per year, but I'll let others with more track time chime in. I think in general our cars can hold up to the occasional DE event without many, if any, mods from the factory setup.

Speed2k

FWIW, there's a thread on here where the OP upsized his rear rotor using a Sebro slotted rotor from another Porsche.

ktnielsen

They will be fine for three weekends and daily driving per year. As I became a better driver my rear pads started lasting longer due to less traction control engagement.

Pappagray

They will survive, but the base brakes really aren't that great at getting rid of heat. What's the price delta between oem and Giro? I know it wasn't much up in here Canada when I did them

ERinEC

I read about that but can’t locate where to buy necessary spacers.

ERinEC

About $800.

jakermc

You will be just fine with OE. Keep in mind the 991 GT3 came with cross drilled rotors also. Slotted is preferred but cross drilled is not going to hold you back, especially at beginner or intermediate driving levels and in frequent track use. I would be more concerned about changing the pads and fluid, as OE street pads and brake fluid will be your first failure point, not the rotor.

I have a virtually brand new set of Endless ME20 pads and Sebro rotors that I took off my Carrera T. I think the rear is the same as the S, only your set-up in the front is different. If interested in the rear, let me know as I'll let them go at a very reasonable price. I am running AP Racing now.

ERinEC

Yes, I change fluid and pads and use the ME20 as well. Thanks for the offer to buy your rotors and pads. I already have the rotors, might reach out regarding the pads though.

Martin S.

A pair of one (1) piece stock rear rear rotors, runs from $130 to $278 ea., $260 to $556 a pair. But they are one (1) piece. See Pelican Auto Parts for their offering. For Dealer pricing, I use Gaudin Porsche, no sales tax in Nevada, and excellent pricing.

Or, look at this as an opportunity to upgrade to genuine two (2) piece slotted rotors from GiroDisc. I believe the two (2) piece slotted GiroDisc fitment for the the 991.1 S maybe be available in 350mm. They are for my 991.2 GTS car. Two-piece rotors are free-floating. The cast iron disc can expand radially (outward) relative to the aluminum bell. The cast iron disc will heat up, while the aluminum bell remains cool. Two-piece rotors are less likely to warp or crack from excessive heat.

Are two (2) piece slotted rotors are worth the money? If you're going to the track, these rotors dissipate heat, always a good thing, heat oil your enemy!. They also may be lighter too. Less unsprung weight is always better. In my 991.2 GTS car, running 350mm in dia. all around, front and rear, stock OEM rotors weigh 94.1 lbs. In contrast, GiroDisc weights all around weighs 81.6 Lbs, a saving of (12.5) lbs, 3.15 lbs. per corner.

Suggest your get in touch with Clark Hamerly (chamerly@apexperformance.net) for a quote. He got my GiroDisc front rotors for me and he stocks most brands. He is a Rennlist sponsor providing excellent technical support. I will be getting my GiroDisc 350mm rear rotors soon from Clark.

And finally, the best track pads may be received by the driver engaged in street driving, as generally noisy and may create excessive "dust" compared to stock. Consider running track pads for the track, and street pads for the street. And don't forget to use the the best brake fluid...for me that was MOTUL RBF 660 Racing fluid.

Martin S.

My front rotors needed replacing. I went to Clark Hamerly (chamerly@apexperformance.net) to do some rotor shopping he handles most brands, including GiroDisc. Talk to Clark: He will be a great resource.

Here is the BEEG DEAL about GiroDisc rear rotors for a 991....they supply GiroDisc in 350mm in diameter, 20mm bigger than stock. Also note, GiroDisc are 2 piece rotors, with a "hat" separate from the actual rotor. As a result, you can replace Only the rotors, front and/or rear, when the time comes, reuse the hat. You will also be supplied new mounting bolts. When it comes time for replacement, a set of rear GiroDisc rotors without hats, is about $800.

And note, GiroDisc are about 5 lbs. less per corner contrasted to stock, and as a 2 piece rotor, they will run cooler under stressful conditions. Suggest you have Clark price out a set of rotors, regardless of the brand. that you choose. Clark has very competitive prices.

I have front GiroDisc front rotors that I obtained from Clark. When it is time, I will for to 350mm for the rear. He was very helpful.

DR911s

Doesn't using the 20mm larger Girodisc rotors on the rear positions result in upsetting the OEM front to rear brake bias? Otherwise, the Girodisc conversion sounds very good, especially for those who plan to frequently track their cars. I've had zero problems with stock brakes including pads on my 2017 C2S; my only change is upgrading the brake fluid. I have tracked my car multiple times at Mid-Ohio and Grattan, both of which are tracks that are more technical than outright high speed, and thus not as hard on brakes as some other tracks. I am in the top run group, and many times there are more instructors in my run group than "advanced" students. I get more fun out of the twisties and transitions than outright high speed on the straights which is likely another reason I haven't had problems with the OEM brakes including OEM pads. The OEM Porsche brakes are far better than were the OEM M3 brakes on my E36 BMW.

Tier1Terrier

I'm interested in understanding this better. I don't believe I've ever heard or seen people altering the brake bias following the addition of larger rotors in the rear. That doesn't mean it's not being done.

DR911s

If all else is kept equal [calipers, pads and brake fluid pressure] the fact that the radius of the pads on the rotor has increased [by 20 mm] necessarily means that the torque produced is greater.

AdamSanta85

I thought I had a link to the guy selling them in the thread?