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Below is what I’ve found through research and fitment, hopefully this might help someone out considering the upgrade. I'll update once they're setup and I have feedback for everyone.
Test Fitment for HRE, Note the hub centering ring, as the screws won't work to hold in place (different location)
My car is a 93 968 without MO30 (this setup won’t work w/ MO30). However, I believe this setup should also work on late model 944’s. Additionally, you might be able to swap out slightly different parts like using a different 350mm rotor (like from a Cayenne) or different 6piston caliper (perhaps 997, or other 996 variant). However, I had fitment concerns with the limited info I could find saying it may or may not work. I spent a little more money and played it safe(r). There are some other threads here on the subject that I researched before I pulled the trigger instead of just going with the normal Big Red upgrade.
Here are some of the examples on part differences: the thickness of the Cayenne rotor and I believe the hat height and hub dia. are slightly different but probably aren’t enough to be an issue (except if you plan to use the centering ring, could always have customs ones made but figured the rotor cost isn’t that much more to justify that). But of note the Cayenne 6 piston caliper isn’t a radial mount (neither is the 944/968 but the adapter I used wouldn’t work, and I don’t know if it’s physically possible to make one for that application), and not all the pistons are ceramic on the Cayenne either. It’s been reported the 997 calipers aren’t the same as the 996 but I don’t have any proof/measurements or any other details.
At this point all I’ve done is a test fit to take measurements for my HRE’s. I’m still running factory 16” rims and there’s no way those will fit over 6piston calipers. Also I hate to install suspension and brakes until after I’ve painted the car.
I basically had no fitment issues. The only problem I had was with the spindle dust shield. It will need to modified with a dremel or you will think the caliper adapter isn’t right as one of the bolts won’t line up. This note will save you 10min of confusion with the adapter and a lot of stress/frustration! When I finally go together I'll run a new ducted one to connect with my 993 Turbo ducted fog lights.
Caliper hitting shield Notch made for clearance Caliper adapter Baby stock brakes if anyone wanted to see
For now I plan to leave the rear calipers stock and just install new pads, drilled rotors, and install a 5/33 bias valve. If you want to upgrade the rears there are several options there, including the 996 GT3 rear caliper and 330mm rotors using an adapter!
997 GT3 350mm rotors: 997-351-405-01, 997-351-406-01 (Sebro’s from AutohausAZ)
Caliper Adapter: 9Products (eBay: Kevin @ Kevin3681 / 9Productsamerica) 9P-baf44-TGT
Rotor Centering Ring: 9Products (eBay: Kevin @ Kevin3681 / 9Productsamerica) 9P-44rc-98 (Make sure to get the right ones- there are two sizes. For the 350mm 997 rotors you want the 98mm)
Below is what I’ve found through research and fitment, hopefully this might help someone out considering the upgrade. I'll update once they're setup and I have feedback for everyone.
But of note the Cayenne 6 piston caliper isn’t a radial mount (neither is the 944/968 but the adapter I used wouldn’t work, and I don’t know if it’s physically possible to make one for that application), and not all the pistons are ceramic on the Cayenne either. It’s been reported the 997 calipers aren’t the same as the 996 but I don’t have any proof/measurements or any other details.
Interesting solution. BTW - the pistons are never ceramic, it is the insulator pucks. Your calipers have the ceramic insulators, as evidenced by the visible yellow color. AFAIK all six-piston calipers from this era of VAG have ceramic insulators. The ceramic insulators frequently crack. AFAIK all the street 997s have ceramic insulators too.
All gen-1 Cayenne calipers are indeed axial mount, except for the Turbo S which is radial (and uses a factory adapter to fit on the same upright). But that caliper is designed for a ~380mm rotor IIRC.
If that adapter is aluminum, I would reconsider threading into the aluminum. With all the heat and vibration in a brake system the AL threads typically can pull out.
Modern radial-mount calipers are often attached with bolts threaded into aluminum, but the bolts go very deep and are in a very thick section of aluminum. Motorsport cars use studs instead of bolts, probably to minimize the torque cycles of the threaded aluminum for a caliper service (modern cars VAG cars require caliper removal for pad service).
Nevertheless, its an interesting solution, especially if the 320mm rotor (Big Red) isn't sufficient.
Last edited by FrenchToast; 01-30-2019 at 01:06 AM.
Interesting solution. BTW - the pistons are never ceramic, it is the insulator pucks. Your calipers have the ceramic insulators, as evidenced by the visible yellow color. AFAIK all six-piston calipers from this era of VAG have ceramic insulators. The ceramic insulators frequently crack.
All gen-1 Cayenne calipers are indeed axial mount, except for the Turbo S which is radial (and uses a factory adapter to fit on the same upright). But that caliper is designed for a ~380mm rotor IIRC.
If that adapter is aluminum, I would reconsider threading into the aluminum. With all the heat and vibration in a brake system the AL threads typically can pull out.
Modern radial-mount calipers are often attached with bolts threaded into aluminum, but the bolts go very deep and are in a very thick section of aluminum. Motorsport cars use studs instead of bolts, probably to minimize the torque cycles of the threaded aluminum for a caliper service (modern cars VAG cars require caliper removal for pad service).
Nevertheless, its an interesting solution, especially if the 320mm rotor (Big Red) isn't sufficient.
Thanks for the additional information, and my apologies for any errors in the post. I appreciate a fresh look on the subject and confirming/updating, as some of the info was dated or questionable.
Yes it is aluminum, but the machinist must have also thought of that and used a Helicoil for the 2 threaded bolt holes. I also found in a previous post where it was suggested once installed, future caliper removal would best be done by removing the axial bolts.
Yes Porsche/Brembo changed the design with a fixed center support where the calipers have to be pulled- a complaint I've heard mentioned on newer 6 pistons. I'm not sure when the change was made, maybe around 2013, looks to be w/ the 991, but I'm pretty sure that wasn't the reason the 997 doesn't fit, as I believe them to be the same overall design.
Yes, Porsche switched to that style caliper with the 991/981 and current-gen Cayenne models. It is a variation of the current Brembo GT. Several VAG cars use that design, as do performance cars from other brands. Supposedly it is to increase stiffness, others argue it is simply a measure to bring more people to the dealer ("how do I change these pads?"). It's not known if the integrated bracing is appreciably superior than a removable pin (or two). The integrated bracing is likely cheaper to manufacture than one with a removable pin - less parts to assemble. So my guess is they are trying to decrease cost while maintaining stiffness.
Porsche Motorsport calipers have similar integrated bracing that prevents pad change, but those calipers are mounted on studs and have a dry break. For a pad change I'm sure they can swap the whole caliper in less than a minute.
Also, its worth mentioning for anyone investigating the 17Z/18Z calipers off the gen-1 Cayenne (like those in Ryan968's first post): due to their popularity as a VAG upgrade, the market has been flooded with cheap knock-offs (some really say Brembo on them). Be sure you get a genuine Brembo unit.
Is there good data on the braking difference between the factory 968 setup and say the 968/M030 setup with the bigger calipers. As with motors people can dyno the results make adjustments and feel good about the changes they have made. With brakes it seems like an all out arms race for bigger and bigger with what gains and measurements? The stock 968 brakes feel like they could throw you through the windshield in a "momentum" car with good pads/rotors but I suspect the hard thing to measure is after an hour of serious driving the difference in heat/fade etc... Im sure adding LS type power requires improvements in braking to compliment the power. Anyone have stopping distance data between the factory setup and M030 setup?
Only thing I've ever heard regarding brake performance (which sets Porsche apart from the competition) was the 100-0 mpg test conducted 10 times in sequence with no brake fade. Probably just hyperbole, but certainly sounds impressive.
Is there good data on the braking difference between the factory 968 setup and say the 968/M030 setup with the bigger calipers. As with motors people can dyno the results make adjustments and feel good about the changes they have made. With brakes it seems like an all out arms race for bigger and bigger with what gains and measurements?
It's just a torque calculation. Function of force (friction) at X distance from centerline.
They use brake dynos for industry testing, not many independent shops are going to have one though.
Last edited by FrenchToast; 02-01-2019 at 03:53 PM.
Yeah, would be tough for individuals to create a real world comparison due to frictional coefficient differences - different brake pad compounds as you mentioned, tire condition and size, different rear brakes, etc.. And I doubt anyone out there would be willing to buy and adapt all different setups to the same car so we could find out what different braking distances are.
IMO, I think there's a lot more to it than just clamping force at a distance from centerline. It's been a while since I took Hydraulics, but I'm pretty sure increasing the piston size will increase area and therefore the force applied to the pad/rotor. 1 piston isn't equal to 6 pistons unless the 1 piston has the same area as the 6 combined, in that case then heat dissipation would be the advantage over 1. To me, more pistons equals more area and more force applied, which equals more friction?
Also, notice the difference pads for different setups. I know which brake pad I want Brake pads: Stock, Big Red, 6 piston GT3
Last edited by Ryan968; 02-01-2019 at 08:24 PM.
Reason: Clarification of info
Also, its worth mentioning for anyone investigating the 17Z/18Z calipers off the gen-1 Cayenne (like those in Ryan968's first post): due to their popularity as a VAG upgrade, the market has been flooded with cheap knock-offs (some really say Brembo on them). Be sure you get a genuine Brembo unit.
Good tip, I didn't know there were knock offs out there. Glad I went through a dealer!
It's been a while since I took Hydraulics, but I'm pretty sure increasing the piston size will increase area and therefore the force applied to the pad/rotor. 1 piston isn't equal to 6 pistons unless the 1 piston has the same area as the 6 combined, in that case then heat dissipation would be the advantage over 1. To me, more pistons equals more area and more force applied, which equals more friction?
What you're saying is true. If you had access to all the numbers, I suspect the pressure at the pad is similar between stock, big red, and GT3. At the end of the day, they are stopping the same tire with the same coefficient of friction. As you suggested, the real advantage of big brakes is their ability dissipate heat so that they can better sustain repeated braking events.
Cool project. At what point will increasing the brake piston area over stock cause a mushy brake pedal due to the increase in brake fluid volume being displaced with each pedal stroke?
IMO, I think there's a lot more to it than just clamping force at a distance from centerline. It's been a while since I took Hydraulics, but I'm pretty sure increasing the piston size will increase area and therefore the force applied to the pad/rotor.
Correct. I was thinking just if you increased piston count but piston area stayed the same.
(If you want, you can edit your post #8 so you're not quoting my misinformation)
Yeah, would be tough for individuals to create a real world comparison due to frictional coefficient differences - different brake pad compounds as you mentioned, tire condition and size, different rear brakes, etc.. And I doubt anyone out there would be willing to buy and adapt all different setups to the same car so we could find out what different braking distances are.
IMO, I think there's a lot more to it than just clamping force at a distance from centerline. It's been a while since I took Hydraulics, but I'm pretty sure increasing the piston size will increase area and therefore the force applied to the pad/rotor. 1 piston isn't equal to 6 pistons unless the 1 piston has the same area as the 6 combined, in that case then heat dissipation would be the advantage over 1. To me, more pistons equals more area and more force applied, which equals more friction?
Also, notice the difference pads for different setups. I know which brake pad I want Brake pads: Stock, Big Red, 6 piston GT3
Increasing the number of pucks in the caliper helps the alignment of the brake pad with the rotor. Adding more pucks adds more contact area for the brake fluid and increase the volume of brake fluid required to fill the volume. If the change in volume is significant vs the OEM brake caliper puck volume, then the front brake system could be compromised, not sufficient volume of brake fluid supplied when the brake pedal is depressed.
The solution is a MC with a larger piston diameter for the front brakes. If not using separate MC for front and rear brakes, then an integral dual MC with a larger diameter front piston probably has a larger rear diameter cylinder. If the rear calipers are not changed, then the larger rear diameter MC piston applies less pressure to the rear brakes and the brake bias moves more to the front
Correct. I was thinking just if you increased piston count but piston area stayed the same.
Very true, that would be right. And actually, I found an old thread 6 Piston GT2/GT3 calipers, see post #86, which says piston area isn't that much different (3877mm vs 3475mm). Not sure on the source or accuracy though.
If the change in volume is significant vs the OEM brake caliper puck volume, then the front brake system could be compromised, not sufficient volume of brake fluid supplied when the brake pedal is depressed.
You're totally right! I think if it is quite different I would have to reconfigure the entire system or risk issues and pedal travel problems. So if the above info is true, hopefully won't be enough to cause problems. I'll let you guys know, and make sure nothing is around me just in case lol..
01-29-2019, 02:03 AM
Info On 996 6 Piston Brake Upgrade For A 968
