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YOUR RESEARCHGirodisc rotors finally installed
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Install on them - and vice-versa
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New rotors like to have used pads installed on them - and vice-versa
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Yes the cost is high at first, but keep in mind these rotors will last longer (almost twice as long) and when they need replacement, it's only $300/wheel to replace the rotor itself (the aluminum top hat gets re-used).
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The materials used also allow for greater heat dispersion, more carbon apparently...
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Yes the stock brakes are amazing when used correctly for general street/fast road use but the moment you push them hard for prolonged periods you experience the flaws.
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New rotors like to have used pads installed on them - and vice-versa
Replace rotor itself (the aluminum top hat gets re
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Yes the cost is high at first, but keep in mind these rotors will last longer (almost twice as long) and when they need replacement, it's only $300/wheel to replace the rotor itself (the aluminum top hat gets re-used).
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Yes the cost is high at first, but keep in mind these rotors will last longer (almost twice as long) and when they need replacement, it's only $300/wheel to replace the rotor itself (the aluminum top hat gets re-used).
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Upgraded the front rotors from OEM cross drilled to Girodisc slotted.
The Girodisc are 8% larger (340mm vs 317mm) and fit using the stock caliper with a reduction in weight from 9.0kg to 7.8kg per disc. The increased diameter provides a larger effective radius giving more braking force for the same system pressure. I really didn't want to go down the Brembo BBK route requiring almost a complete new disc/caliper system and pressure/bias changes.
Here you can see the quality...
And here the size comparison with the OEM...
It's a very easy install, the only difference to the usual disc change is the addition of the 12mm spacer to move the caliper further away from the arm. The spacers are included in the kit together with 12mm longer caliper bolts (strangely Porsche part numbered?).
Finished...
Thanks to Craig at rennstore for all the info and help...
Now I just have to see how they compare on track...
that looks like a mod worth while and easy. I agree on the spacers. I think a nice one peice spacer that looks like it is supposed to be there would be better.
Why would a one piece spacer be any better? It's just added weight, you're not doing it for looks as it's never seen. The spacer design is perfect for the application and has been race tested.
I agree on the caliper size thing hence keeping them black, red would stand out too much, but it's only marginal. Like I mentioned before though if I wanted bigger calipers etc I would have gone down the GT3 6pot route but then you're talking $1000s more...
Let us know how the new rotors perform compared to OEM without upgrading the calipers. You are probably doing this for the track as opposed to street use? They look great.
First and foremost, the rotors look badazz and like quality pieces..I pm'd craig myself and am interested in the upgrade vs cost factor...
I'm not an engineer, but I have been wrenching for 28 years on everything from beaters to hi-performance muscle cars. The single piece spacer for one allows for a solid contact between the caliper and the mounting surface. I haven't witnessed the effects of heavy braking on these items first hand, specifically on P-cars, but I imagine there are some forces involved and alot of heat generated.
I would think you'd want to spread some of those forces and heat uniformly from the caliper, not just thru those two 12mm thick washers. the air moving in that gap is not going to do squat to have a cooling effect.
my other .02...
- and the spacers look cheesy.
Curious why they would not make them as direct replacements to the stock unit and not require the spacer.
Has anybody that purchased these MEASURED the rotor area and compared to the stock units? In other words, measure the width of the rotor that is from that area where the hat ends and the rotor edge ends.
just looking at the pics... the stock is def smaller. It will be hard to make a 2 piece the same size as the stock.
the stock is 317mm vs 340mm... so the radius is longer... the advantage with this rotor (aside from heat dissipation?, fade etc? weight) is since the pads are further out, the stopping power is greater (more torque).
Makes sense. I'm just curious of the actual SURFACE AREA of the two rotors. While the giro has a radius of 11.5 mm more I'd still like to know if the area is larger and by how much. Still don't understand why they can't make a stock replacement that would not need the spacers.
surface area looks the same to me..... used my thumb as a ruler.
If you look at the diameter of both top hats... they are both the same. This diameter is needed to fit in the hub/axle. Now add the extra space needed for the mounting bolts for the disk... that where the extra 11.5mm is lost. Thats why it needs the 12mm spacer for the calipers. They cant make those disc mounting points inside the hats cause that area needs to be empty for the axle/hub... does that make sense?
If that picture is to scale, then the measurements I just took are the same as well. So, back to my original question....
If the surface area of the two rotors is identical, then how is braking heat dissipation better? What about actual stopping power?
Trying to understand how these are better at $2200 versus $540 for stock at all 4 corners?
thats why I put heat dissipation, and fade in ??? in my statement. Weight is clearly an advantage and maybe my torque comment is true as well. If the replacement disc are cheaper than stock... that is another advantage.
Sorry, the scientist in me keeps asking.........
Is the heat dissipation significantly greater than stock? How was this measured?
What are the weights of stock and Giro?
The weights are in the original post, the larger disc has more surface area as the larger radius means a larger surface area even though the contact 'width' doesn't change...
Therefore increased surface area = increasing cooling = less fade
Also, decrease in unsprung weight. The Girodisc front discs offer a 18% improvement in surface area-to-weight for the rotor.
And, increased braking:
Torque = Force x Distance, brake torque is equal to the retarding force provided by friction between the pads and discs, multiplied by the radius of the contact point between the pad and disc. The increased diameter provides a larger effective radius, or torque arm the pads act upon, giving more braking force for the same system pressure...
The materials used also allow for greater heat dispersion, more carbon apparently...
Dervish, did you weigh them before you installed them? Trying to figure out what the weights are before and after (both front and rear). Is the weight reduction you stated (9 to 7.8 kg) for just the fronts?
As far as suraface area, it wold be easy to get a number for both stock and these Giro's with simple calculations. I think this would be good info as well to have in this thread for people who do searches.
Devish, are these being used for track applications in your case?
I think that you gentlemen might be missing the fact that the overall diameter of the rotor is larger, even though the measured width of the pad surface at any given angle appears the same.
Imagine an 8-slice pizza that you add a 9th slice to. While the length of each slice on its cut is the same, the overall diameter grows larger and a circular hole appears in the middle of the pie.
So there's more swept rotor surface, which should aid in heat dissipation. I can't vouch for the overall performance of the rotors (and I'm no fan of the slotted look) but it's a fact that you're getting more rotor surface. 75% more in proportion to the added cost? Probably not. Dervish, I'm trying to understand your claim of a larger effective radius for the same contact area on the pad leading to more braking force. It's not that I don't believe you, it's more likely that I'm a poor mathematician.
Considering the stock braking performance built into every P-car to match its stock performance, this might be a solution for the driver who outbrakes their car on a consistent basis. I think that demographic is small. I track my car and I don't see fade in my rotors until the end of a few VERY hot runs, and even then it's progressive. Stock rotors, stock pads on a 997 C2S. I'm not the quickest car out there but I get along. My only complaint is dust and pad wear, which I'm compensating for with track pads this season.
Dervish: what part of your experience with the stock rotors led you to this purchase?
Not missing that at all. This is why I asked for the inner opening sizes. We can figure this out very easily. Calculate the area of the ENTIRE rotor for both stock and Giro (we know this already) and SUBTRACT the area of the non rotor area. This will give us not only the exact swept rotor surface but the difference between the two.
First set of numbers (before getting the center section measured to subtract out):
Giro Area
F (140.53 sq in)
R (128.61 sq in)
Stock
F (122.7 sq in)
R (109.3 sq in)
Need the measurement (diameter) of the inner section to finish up
do they make this rotor for turbo sized rotors F/R? what is the cost differential. I was looking at replacements and OEM still came out cheaper for my car unless this has changed.
I much rather have slotted than cross drilled rotors, especially for the track.
Oh, and agreed on the 12mm single piece spacer rather than washers.
Ok, allot of questions.
I do track the car but not excessively. Maybe about once a month, one next Saturday at quite a brake heavy track so will get a good comparison. I do get fade even with SRF fluid and GT3 cooling ducts at this event. Have another 'RS' trackday 2 weeks later then a long weekend at The Ring the following month.
I really wanted a reduction in unsprung weight, increased braking force and reduction in fade without the need to go heavier and '6pot', that's when you really start spending big $$$$.
Another added bonus is hopefully the elimination of the dreaded inner surface rust/corrosion. This has always been a big problem with stock rotors, time will tell on this one.
I also can't rule out aesthetics, I actually really love the slotted look, plus no more drilling out blocked holes or measuring cracks...
Now the manufacturer info... Check this link out
http://www.cargraphic.de/sources/dow...rodisc-web.pdf
It shows stock weights and dimensions versus Girodisc.
'number9ine' Think of it like this - A force applied at a right angle to a lever multiplied by its distance from the lever's fulcrum (the length of the lever arm) is its torque. A force of three newtons applied two meters from the fulcrum, for example, exerts the same torque as a force of one newton applied six meters from the fulcrum.
Torque = Force (caliper piston) x distance (disc radius)
I also don't believe that Porsche put the best braking system on the cars from factory for ALL users. Just as they don't with suspension. Yes the stock brakes are amazing when used correctly for general street/fast road use but the moment you push them hard for prolonged periods you experience the flaws. Hence why you can upgrade GT3 brakes to Alcons etc, surely you'd expect GT3s to have the ultimate brakes from factory?
Also have a look at this for all the manufacturer details...
http://www.girodisc.com/catalog/prod...roducts_id=915
Yes, you have basically covered it all.
You get better braking by pushing the caliper out another 10mm, thereby achieving more leverage with the same sized calipers and pads.
Yes the cost is high at first, but keep in mind these rotors will last longer (almost twice as long) and when they need replacement, it's only $300/wheel to replace the rotor itself (the aluminum top hat gets re-used).
These rotors are handmade here in So Cal by RSS. A very good company, and a great facility.
I'm still trying to understand the "why" of these at $2200 (4 times the cost of stock).
Heck, the PFC 2-piece setup is cheaper than Giro.
Sorry, but I am not understanding the rationale for buying these. The braking system on these cars is phenomenal. And if you are boiling SRF (which I highly doubt) then there is something else at play. The proper brake cooling (cup ducts not the GT3 ducts and maybe even some ducting for additional airflow) and you will be just fine. And at Only $300 for a complete set of front replacements, you will need to go through a lot of rotors to get a descent ROI.
In VERY HARD braking situations I've used many different rotors, pads, fluid, etc in all the various 996 variants and this one doesn't make sense to me.
Just my $.02
I have a comment on aluminum hats on the 996 GT3, several of my pals switched from Cup rotors to floating rotors with aluminum hats. They espoused the "cheaper because I change only the rotors" argument. Imagine their chagrin when they discovered that the bolt holes in the aluminum hats had become enlarged (ovalized in fact) and the hats AND the rotors needed to be replaced. Those were Brembos as I recall, so the Girodiscs may be superior. Like Dell, I found that Cup brake ducts, and RS 29 pads in front with RS 19 pads in the rear gave me 40 or so days on my front rotors and about 70 on the rear. The harder rear pads improved brake balance too which on the 996 GT3 was way too biased towards the front.
Here was my rationale...They could last up to twice as long, there's half your money back...they don't have holes so no cracking (even though I don't track)...a little less unsprung weight...and they look nice. That being said I did only replace the fronts w/ Girodisc because of the high cost vs OEM. If it turns out that the aluminum hats don't last and aren't covered by warranty, then I would go back to OEM.
They came to England from moi here at Rennstore.com -
Indeed they last loads longer and offer several moderate benefits...and are easier on pads too acc'd to Ye Olde customer reports --
I understand what you guys are saying but I was not happy with the stock fronts.
'LVDell', I'm not boiling the SRF fluid, this is a preventative measure together with the added weight and size benefits. If you factor in the cost of cup ducts ($270 ish) and new OEM rotors twice or even 3 times as fast the price comparison is not too bad. Plus you only have to replace the disc not the hat next time. I know it's still more money but then that covers the additional benefits (IMHO).
I also looked at the PFC (almost ordered them but that's another story) and they are almost the same money (as you have to use PFC pads too), plus they are HEAVIER than stock (9.2kg vs 9kg OEM vs 7.8kg Giro) with no size benefit, what's the point????
I even understand that without running Toyos or Cups the braking is only as good as the rubber/road contact.
This is an expirement and one that I'm very happy with. It's not for everyone and the initial price is high but for what I wanted I figured it was justified, especially compared to the alternatives.
Craig, got a question. When I eventually make the step to GT3 can I use my existing bell/hat and fit larger rotors, effectively meaning I don't have to buy a full new set?
Thanks.
The problem with Aluminum centres/hubs is that while aluminium is light...is also pretty soft.
In a purely race application, you would definitely warp the mounting holes on an aluminum hub, but the weight savings and modularity of a two piece setup might be enough to outweigh the cost. If you are finding the extra 2 Kg (reported) of unsprung weight a measurable advantage, you wouldn't mind paying for new hubs/rotors. But is the stock setup with these rotors best for racing? I guess that depends on the class restrictions and your budget.
In street use, you can probably get away with keeping the same hub for a couple rotors....but realistically, on the road...those rotors should last you for years.
Anyone actually racing with these care to comment?
I love the look of these and would love an excuse to upgrade. I'm as addicted to upgrade **** as the next guy...
But FWIW, I have to say that the brakes are something this car got right. They're just stupid good. You can find brakes that give you shorter stopping distances, but it's a lot harder to find brakes that can perform on a track, where fade and consistency matter so much more than a few feet at full lock. And then there's durability. In street use, I'm still on original pads and rotors at 101,000km. Here's an interesting article that discusses the 911 brakes in a competitive context.
http://www.caranddriver.com/features...ce_cars_page_4
I hope they kick *** for you and I'll be interested to hear if they do. The stockers are just so hard to beat.
For track use they are sooo much better - first of all they are not 317mm as stock - they are 340mm, just 10mm shy of the GT3 rotor in rotor size.
The heat capacity increase is significant, and the longevity is hard to beat. Plus, they sure cost a heck of a lot less than Brembos.
I'm using them on track with Pagid RS29 front and rear and they are amazing, never get fade. The combination does squeal a little on street but I like that motorsport sound..
As an extra I'm also running lighter track alloys, my logic is get as much unsprung weight off the car, for performance and for longevity of components.
This girodisc combination in front needs:
Only the discs 340mm, the kit brings all the need?
We use the OEM calipers, and need to buy only the discs?
Maybe I'am interested.
Price of the discs kit?
Soon as my OEM rotors and brakes pads finish, I thinking in the front Girodisc, with Performance Friction 06 pads, front and rear.
I have now 997GT3 cooling ducts, to change for the 996cups, the SrF racing oil, and goodridge brakes lines.
Mine are still at 27.1mm after ALOT of track days and over 18 months use, and that's running RS29 pads, even they have a load of life left in them. Seriously impressed with their durability.
