mdkim

I've also found the stock pads lacking in initial bite and requiring a significant amount of pedal travel to slow the vehicle (both on street and track). After switching to PFC11s my brakes have a touch more initial grab (may be imagined) but require much less travel before full ABS kicks in. I have not tracked the car after the swap so my thoughts may change after I track the car again.

Ideally I also would like a bit more initial bite for street driving. For tracking, I don't mind excess pedal travel for better modulation.

MayorAdamWest

Agreed with what you say here. This is how I'd describe my feelings, except I don't like the street feel.

Mech33

Hey Joe do you know what the brake fluid volume need is for a full flush of all 4 corners?

orthojoe

Good question. I never know exactly how much to use. I just keep on bleeding until the color of the fluid changes. The OEM fluid is paler in color than the RBF600 I 'm using. IIRC, I used about 2 bottles of the stuff.

orthojoe

That's no good at all. Yeah, I'd be happy to meet up some time. I'll be at MRLS on 5/22. When are you out at the track next? We can also meet up some weekend.

orthojoe

Let us know once you do, I don't think the OEM fluid is very durable, so I'm guessing you'll see at least some improvement with new fluid. OEM felt fine to me the first 2 track days, but started to degrade after that and the pedal started to feel softer. RBF600 made it feel better than new.

I think you are feeling ABS. I've noticed that it doesn't take as much effort to lock up the wheels in the GT3 as in other cars. I don't hammer the brake pedal as much as I did in the spyder, because ABS engages more readily

MaxLTV

Regarding brakes, some points may help those experiencing problems:

1. No bite - GT3 intentionally comes with significantly less brake boost than other 911s (for better modulation), which is noticeable, especially when comparing to luxury cars, which are heavily boosted. Another factor is that GT3 has no brake priming (thanks god!). I passionately hate this feature on other cars, but basically what it does it makes the first 5% of pedal pressure make 20-60%+ of braking effort, depending on how quickly you released the throttle pedal and how noobie the target audience of the car is. Some of the more "mass-markety" cars go to full panic stop mode if you release throttle very quickly and tap the brake. Performance cars have this turned down or not present. Once you get used to it, it feels like performance cars have no initial bite, and is often blamed on aggressive pad compounds and other things. It's very noticeable when switching between different types of cars. The car that you are used to more will feel "right" and the other one will feel broken :-). I could not enjoy driving a loaner base Cayman because of that.

2. Vibration and possibly softness/travel - GT3 vibrates the pedal not only on ABS but also on stability control interventions. I do not like it either. Also, when it vibrates the pedal, it seems to get softer and travel further - not sure if that's reality or perception, but I definitely noticed that. It feels like vibration leaks the pressure from the system somehow. I do not like it. It does not happen in traction control only or all off modes to me, or when I do not let stability control interfere.

Otherwise, my brake feel is very nice and confidence-inspiring.

bigkraig

I think #1 is why I hate audis so much.

Manifold

Interesting, thanks for this. Nice to know that at least some of this stuff isn't just my imagination!

On #1, I can see how reduced boost may explain some of what I'm experiencing, and that it does allow for better modulation.

On #2, I'm suspecting that the car doesn't like my trailbraking and stability control is intervening (but without flashing a big PSM light). I may try turning stability control off, but since at least one pro has said there should be no need to turn it off, maybe I just need to adjust my driving technique and trailbrake less. I too feel that, when the pedal vibrates, it travels more and softens - and I don't like it either!

MaxLTV

I actually second not needing to turn off stability control in most situations, if at all. It's lenient enough. Better to drive within its confines - it's probably the faster way anyway.

Mech33

Yes this #2 is exactly what I am experiencing on track. When I brake hard going over the hill into the corkscrew turn 8 at Laguna, I get the vibe and the pedal goes softer.

It's the pedal going softer they makes me feel like the brakes are failing... not confidence inspiring, but it sounds like I'll just have to get used to it.

Clark-ApexPerformance

If you are going to run on the track with the PSM on plan on replacing your rear pads and rotors on a much more frequent basis.

orthojoe

Actually, that's not entirely true.
I leave PSM on on my spyder as well as my GT3, and the rears will FAR outlast the front. As others have stated, PSM only intervenes if you've done something wrong. Hopefully you're not doing something wrong at every turn. Smooth is fast.

On the other hand, my buddy's 997.2 TTS runs through his rear brakes at at least 2 times the rate of the front.

I'm not totally sure why there is a difference. I used to think it was because of PTV. My spyder didn't have PTV and the TTS did. However, the 991 GT3 has PTV and the rear brakes don't take anywhere near the amount of punishment that the fronts do. My only thoughts at this point are:

1) Porsche changed something with PSM/PTV where the rear brakes aren't overworking themselves
2) My buddy's driving style has him constantly bouncing off PSM.
3) There is something about the TTS that kills the rear brakes

MaxLTV

I experienced the same - I run with PSM on most of the time, and my first set of rear rotors looks better than my second set of front rotors now. So it's better than 2 to 1 ratio. I do not know why such a big change from one generation to another. My hypothesis - the better diff on 991 helps, so it does not use brakes for traction control. But that's just a guess, and I have no supporting evidence.

Clark-ApexPerformance

Interesting most all the 996 and 997 guys running with PSM on
We're burning up their rears. Either you guys are doing a much better job of driving or the 991 PSM is somehow different.