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That was the thought, but guys are reporting that the pads are still tapering with track use.
Yup, that is correct. The closed off bridge on the 991 GT3 caliper can make it more rigid but brake pads can still taper. My Z06 brake pads - both OEM and endless ME20 taper alot but when I change brake pad compound to RB XR70 - running same giant Brembo caliper the tapper became minimal. There are many reason why brake pads taper such as sticky caliper cylinder, brake caliper cylinder location/size and brake pad compound
Pad taper can occur in either or both the short axis and long axis of the pad. Stiffening the caliper at the top tends to help some with both. The staggered diameter pistons affects taper on the long axis of the pad.
That was the thought, but guys are reporting that the pads are still tapering with track use.
Another problem is heat. The hotter you get the stock caliper, the more flex it will allow. Two piece calipers don't suffer from this. The bridge is there to help make it as stiff as they can but everything has it's tradeoff.
First thought I have is WOW! What the heck is Porsche doing? First the impossible and impractical center lock wheels
There are some hot discussions in various threads about this topic - Center Lock, how hard or not to remove and install correctly may be somewhat debatable, nonetheless I like to illustrate the difference mechanically/physically between the two so that you can evaluate and exercise your own discretion in making such a choice. It's not just a matter of cost & how easy/hard on maintenance, more importantly it's the safety concern.
From above illustration, you can see automotive industry designs a hub follows the rule of physics and strength of material and below 3 criteria are related to the horsepower and weight of the vehicles:
1. The bolt size (M12 or M14)
2. The PCD (pitch circle diameter), from 100 to 150mm
3. The number of bolts (4, 5, 6 or 8)
So a smaller car can use smaller hub, bolt and least number of bolts, but as the vehicles get bigger and heavier, so is the bolt size, hub size (PCD) and number of bolts.
These bolts are used to transmit the torque from the shaft to brake rotor and wheels/tires, and the PCD is the leverage which subject to shearing stress, so you can now compare the leverage of a Center Wheel Lock vs. the conventional 997TT lug bolts
We also learn from the conventional wisdom; Don't put all your eggs in the same basket, if you don't disagree then you shall the risk of one single basket - Center Lock.
I bet you see someone drive his/her car with 1 or 2 broken studs or no wheel nuts, but definitely you will never see any Porsche owner drives a GT3 with a loose or missing Center Lock.
Originally Posted by mikymu
and now the brake calipers that's completely seal off to prevent a quick brake pad change? One reason why they are design this way (not for efficiency) is to make owner take their car to the dealer for service. Funny how they also run the sealed off PFC caliper on 991 Cup and only when you move up the pecking order to "real" racing where race cars actually have pit stops and time and speed for component change is life and death matter do you see the Brembo calipers equipped with brake pads quick release access from the back shown below on the 991 GT3 RSR
I have faith that Warren will come up with a much better designed caliper with easy brake pad access. Taking calipers on and off for any car is not fun and required for brake pads change is just backward in engineering
RB Caliper kits would offer alternative to GT3 owners for brake efficiency improvement, and convenience of maintenance over OE set up.
They are offered as an optional choice for someone who are looking for better performance and durability, just like our brake offer for Nissan GT-R owners who frequently tracks their cars.
We look forward to working with you towards this goal.
Besides the hydraulic bias mentioned above, rotor size and pad effectiveness bias and installed p/v affect bias.
I like to use a single # the front to rear ratio to sum up bias
for instance a 2007 GT3 street car has a hyd bias of 1.931 which goes to 2.084 when rotor bias and pad effective area bias is factored in, I didn't run the numbers for the effect of the p/v
For my own cars(both w/ 993RS brakes) I have run the #s
hyd 1.472, w/ rotor/pad bias 1.426 w/ p/v 2.970, one runs w/o a p/v the other w/ stock 993p/v's
I also ran the #s for a 2007 GT#RSR w/ dual master setup
hyd 1.504, w/ rotor/pad bias 1.613, no p/v but w/ cockpit adj. dual master bias control max 1.875 min 1.260
Very true, but here we are focusing on caliper piston sizing. Basically total piston area and rotor size (diameter) are two principal criteria in a balanced brake system design, assuming the rotor material and pad compounds are equal, which as you indicated can be further fine tuned and alter the bias.
Here is the piston sizing comparison on some of the modern super muscle cars, that we have brakes upgrade/kits offered (except GT3 being developed).
991 GT3 (PCCB) 6 pot/4 pot: (Non staggered front and rear - 30x30x30/34x34)
Area:42.4 /36.3 Total: 78.7 Ratio (%): 54/46
Corvette Z06 (PBR) 6 pot/4 pot: (Non staggered front and rear - 33x33x33/30x30)
Area: 51.3/28.3; Total: 79.6 Ratio (%): 64/36
Nissan GT-R 6 pot/4 pot: (Staggered front 30/34/36, non staggered rear 30/30)
Area(CM^2): 52.7/28.3, Total: 87 Ratio (%): 67/33
Mustang GT500 6 pot/single floating: (Staggered front 30/34/38, rear 42.8 single floating)
Area: 28.75 / 55 Total: 83.75 Ratio (%): 66/34
Total average (excluding GT3): 65%/35% which coincides to the 2/1 general ratio.
Assume Porsche has a reason to make the rear brake more biased than front contrary to the rest of motor companies, then my question is why their rear brakes always thinner and smaller than the front.
Anyone know?
Last edited by RacingBrake; 10-03-2014 at 02:29 PM.
Very true, but here we are focusing on caliper piston sizing. Basically total piston area and rotor size (diameter) are two principal criteria in a balanced brake system design, assuming the rotor material and pad compounds are equal, which as you indicated can be further fine tuned and alter the bias.
Here is the piston sizing comparison on some of the modern super muscle cars, that we have brakes upgrade/kits offered (except GT3 being developed).
991 GT3 (PCCB) 6 pot/4 pot: (Non staggered front and rear - 30x30x30/34x34)
Area:42.4 /36.3 Total: 78.7 Ratio (%): 54/46
Corvette Z06 (PBR) 6 pot/4 pot: (Non staggered front and rear - 30x30x30/33x33)
Area: 51.3/28.3; Total: 79.6 Ratio (%): 64/36
Nissan GT-R 6 pot/4 pot: (Staggered front 30/34/36, non staggered rear 30/30)
Area(CM^2): 52.7/28.3, Total: 87 Ratio (%): 67/33
Mustang GT500 6 pot/single floating: (Staggered front 30/34/38, rear 42.8 single floating)
Area: 28.75 / 55 Total: 83.75 Ratio (%): 66/34
Total average (excluding GT3): 65%/35% which coincides to the 2/1 general ratio.
Assume Porsche has a reason to make the rear brake more biased than front contrary to the rest of motor companies, then my question is why their rear brakes always thinner and smaller than the front.
Anyone know?
I don't know but these comparisons are all with front engine rear wheel drive configurations....logic would say rear engine layout needs slightly rear ratio bias with no need to make them bigger/thicker for weight considerations?
There are some hot discussions in various threads about this topic - Center Lock, how hard or not to remove and install correctly may be somewhat debatable, nonetheless I like to illustrate the difference mechanically/physically between the two so that you can evaluate and exercise your own discretion in making such a choice. It's not just a matter of cost & how easy/hard on maintenance, more importantly it's the safety concern.
From above illustration, you can see automotive industry designs a hub follows the rule of physics and strength of material and below 3 criteria are related to the horsepower and weight of the vehicles:
1. The bolt size (M12 or M14)
2. The PCD (pitch circle diameter), from 100 to 150mm
3. The number of bolts (4, 5, 6 or 8)
So a smaller car can use smaller hub, bolt and least number of bolts, but as the vehicles get bigger and heavier, so is the bolt size, hub size (PCD) and number of bolts.
These bolts are used to transmit the torque from the shaft to brake rotor and wheels/tires, and the PCD is the leverage which subject to shearing stress, so you can now compare the leverage of a Center Wheel Lock vs. the conventional 997TT lug bolts
We also learn from the conventional wisdom; Don't put all your eggs in the same basket, if you don't disagree then you shall the risk of one single basket - Center Lock.
I bet you see someone drive his/her car with 1 or 2 broken studs or no wheel nuts, but definitely you will never see any Porsche owner drives a GT3 with a loose or missing Center Lock.
RB Caliper kits would offer alternative to GT3 owners for brake efficiency improvement, and convenience of maintenance over OE set up.
They are offered as an optional choice for someone who are looking for better performance and durability, just like our brake offer for Nissan GT-R owners who frequently tracks their cars.
We look forward to working with you towards this goal.
Thank you.
Warren-RB
Very good information. Center lock is really a racing technology driven by the need to take wheels on/off quickly during pit stop but I lost count how many times wheels fly off when they are not tighten properly ....
Originally Posted by RacingBrake
Very true, but here we are focusing on caliper piston sizing. Basically total piston area and rotor size (diameter) are two principal criteria in a balanced brake system design, assuming the rotor material and pad compounds are equal, which as you indicated can be further fine tuned and alter the bias.
Here is the piston sizing comparison on some of the modern super muscle cars, that we have brakes upgrade/kits offered (except GT3 being developed).
991 GT3 (PCCB) 6 pot/4 pot: (Non staggered front and rear - 30x30x30/34x34)
Area:42.4 /36.3 Total: 78.7 Ratio (%): 54/46
Corvette Z06 (PBR) 6 pot/4 pot: (Non staggered front and rear - 30x30x30/33x33)
Area: 51.3/28.3; Total: 79.6 Ratio (%): 64/36
Nissan GT-R 6 pot/4 pot: (Staggered front 30/34/36, non staggered rear 30/30)
Area(CM^2): 52.7/28.3, Total: 87 Ratio (%): 67/33
Mustang GT500 6 pot/single floating: (Staggered front 30/34/38, rear 42.8 single floating)
Area: 28.75 / 55 Total: 83.75 Ratio (%): 66/34
Total average (excluding GT3): 65%/35% which coincides to the 2/1 general ratio.
Assume Porsche has a reason to make the rear brake more biased than front contrary to the rest of motor companies, then my question is why their rear brakes always thinner and smaller than the front.
Anyone know?
Rear heavy GT3 need more braking on the butt vs more 50/50 balanced cars like Z06 or M3. Front end is pretty light on these GT3 so if you have "typical" 63/30 brake force distribution then front end will lock up under hard breaking - and the car will not brake well even if you manage not to lock up. In Cup car I can manually adjust brake balance for and aft and when I had too much braking force on the nose or butt the wheels lock up right away - it's a pretty delicate balance and I can feel the braking difference with just one click on the brake adjuster
Very true, but here we are focusing on caliper piston sizing. Basically total piston area and rotor size (diameter) are two principal criteria in a balanced brake system design, assuming the rotor material and pad compounds are equal, which as you indicated can be further fine tuned and alter the bias.
Here is the piston sizing comparison on some of the modern super muscle cars, that we have brakes upgrade/kits offered (except GT3 being developed).
991 GT3 (PCCB) 6 pot/4 pot: (Non staggered front and rear - 30x30x30/34x34)
Area:42.4 /36.3 Total: 78.7 Ratio (%): 54/46
Corvette Z06 (PBR) 6 pot/4 pot: (Non staggered front and rear - 30x30x30/33x33)
Area: 51.3/28.3; Total: 79.6 Ratio (%): 64/36
Assuming those numbers in () are correct then why does the Z06 have more area in the front for the same size? The rear number also looks too small for the indicated value.
I come up with 42.4/34.3 for a total of 76.5 which gives a ratio of 55/45.
Assuming the area numbers for the Z06 are correct I come up with (33x33x33/30x30)
Hello Everyone, I would like to introduce myself. My name is Mike and I have been working with Warren at RacingBrake to develop these different kits for the GT3. My shop, Advance Performance, is located in Tampa FL. Due to the lack of an iron kit and at the request of a few of my local customers, we reached out to Warren to help solve this problem and bring these different kits to fruition. Fortunately one of our good customers was willing to lend us his vehicle for an extended period of time to do the R&D. Now we are pleased to be able to offer quite a few different options that are desperately needed for the new 991 GT3.
As you can see from Warren's posts, These offerings are of the highest quality and are geared toward the track customer who is looking for the best. We hope that we will be able to satisy everyone with the different kits that are designed to address the different needs of Gt3 owners.
The first kits that will be available will be the full blown BBK's. These kits will be offered in 3 different rotor sizes. We are also working with Forgeline wheels to make sure we can supply compatible 19" wheels for the first two kits.
For the customer looking for just an iron rotor conversion in the stock PCCB sizes we are offering the following kit. These kits will have everything necessary to convert including street pads and the availability of track pads specifically designed for the RB rotor. http://www.racingbrake.com/RB-Iron-R...por-irk-03.htm
Lastly Warren has designed a CCM replacement kit utilizing Surface Transform's CCM-X rotor. These rotors will be in OE sizes and compatible with the stock PCCB Calipers. http://www.racingbrake.com/RB-CCM-Re...por-crk-01.htm
In lieu of our help with developing these kits, Warren has asked us to take charge of the sales here on Rennlist. I will be creating a group buy thread to facilitate pre-orders as well as establishing a Rennlist discount in an effort to support the community.
If anyone has any questions, please feel free to PM me.
I would also like to officially thank Keith Henthorne (owner of the GT3 we used) for the donation of his car which has really helped expedite this development.
Assuming those numbers in () are correct then why does the Z06 have more area in the front for the same size? The rear number also looks too small for the indicated value.
I come up with 42.4/34.3 for a total of 76.5 which gives a ratio of 55/45.
Assuming the area numbers for the Z06 are correct I come up with (33x33x33/30x30)
You are correct the Corvette Z06 PBR calipers are 33x33x33 front and 30x30 rear.
09-17-2014, 01:43 PM
