I've run just about every permutation of brakes on these cars you can imagine, including the 380/350 PCCB calipers and the smaller and larger brake cylinder masters. The front calipers are not the reason for the larger master. The reason Porsche switched from the 25mm master to the 27mm master on the 997 cars is due to the fact that the rear calipers have 50% larger piston bores vs. the 996 rear calipers. As such, the 997 rear calipers move more fluid which translates to a slightly longer pedal. By using the larger brake master, the pedal stroke is firmed up with a sharper biting point.

Porsche actually went a step further on the 997GT2/3 cars by again reducing the 380 front caliper piston bores by another 30% compared to those on the 997TT 380 calipers. This further firmed up the brake pedal while at the same time giving the GT cars more rear brake bias. The difference in simply running the GT calipers vs. the TT calipers is very noticeable. Yes, the smaller stock 996 master will work with the 997 brakes but it is not ideal. The brake definitely feel better with the larger master, and even better with the 997 cam driven vacuum assist pump.

 

I made up a batch of 10 of these lines, one with a 10mm and 12mm fitting. I sold the last one about a month ago. I don't plan on making any more unfortunately. This is what the lines looked like:

[url=https://flic.kr/p/dWTmLi]

 

You for sure did way more testing than I did - good work. In my application there is no downside by keeping the 996 stock on the master brake cylinder. The brakes do bite hard and pedal travel is no issue. Not saying that it can't be better - it always can.

 

i guess the one i have just went up in value like a gt2!!

 

Ok if you aren't making any more can you tell me the length of line you used?

 

The length is the same as whatever the factory 10/10 line is. I don't remember the exact number I measured but I wanna say it was about 14". I could be persuaded to make another batch of these but I'd have to have a commitment for 6 of them for it to be worth my time. It was a bit of a pain to make to correct bends along with the flares. I have a high end flaring tool that makes perfect bubble flares but it's fairly time consuming.

 

I've still got one custom line from John laying around here and still deciding to install or not. Anyone running this without PSM disabled and without any Problems? I think nearly all who got the new brake master and custom line installed, got PSM failure, but maybe not up to date.....

 

Can't really say what the issue is with PSM when running the larger master. We think that is has to do with the brake light switch. When you run the larger master the brakes will move more fluid per given pedal stroke. As such, the ABS/PSM module will sense deceleration prior to the brake switch activating. When that happens, you get a PSM fault. I believe it's a simple matter of readjusting the switch to close a bit sooner. This is a guess however as all the PSM components including the yaw sensor and PSM pump have been removed from my car. When I initially made the 10/12 lines, I had my PSM pump disconnected so for all intensive purposes it was not there. I don't think there is really any benefit to the larger master unless you end up running the larger 997 rear calipers. With that said, I believe many of the guys that installed the larger master and my adapter were track guys and ended up disconnecting PSM anyway. That, in and of itself is probably the best mod and solves all the BS issues that come with it.

 

I tried with a brand new brake switch. No success. Maybe, just maybe, if you adjust the pedal pushrod length you might be lucky.
Strange thing here was the fact that when I had hot brakes (= already increased system pressure, like 2nd or 3rd stint at track) the ABS/PSM disconnection was instant at first touch of the brake pedal. At street driving or day's first stint no problems. We all know the feeling when you can't completely trust your brakes.

There's a diffecence with pedal feel indeed.

 

Sorry to get an old thread back. Do you know if 380 PCCB discs/rotors can fit with the original 996GT3MKII 18 wheels? Thanks

 

they will not

 

362mm discs will fit under though.

 

Thanks