nicolae1

Small intro : I have the car for a little more than a year. During this time I had to press the brake in an emergency situation for three times. In every of these situations the car didn’t stop as I expected, but in the first and second situation I managed to avoid the car in front of me because there was free space one side or the other. The last time was not any escape space and I hit back the car in front of me , who stopped for no reason in my opinion , but this is another discussion.

So , in any of these emergency braking situations I felt that the car does not stop as hard as it should be. I thought that maybe the reason was that the brake pads are not warm enough and the car does not have stopping power because of this , or the brake pads are not good enough . But I doubt that this is the reason. Then I thought that maybe the ABS system is not working very well when you press the brake very hard , but I also think this is not the case. My last thought ( and my question to you ) was that maybe when I press the brake in an emergency I also press the gas pedal without knowing , hence the fact the car is not braking as it should be. What do you think ?

When I brake as in daily driving , the travel for the pedal is not very long but in an emergency situation I press the brake to the bottom . This might be the reason that at some moment in time I begin to touch and press the gas pedal too. Did anybody had this kind of braking experience ? Or it is just me. ( Could be because maybe I keep the foot in between the gas pedal and brake pedal- intended for easier heel & toe downshifting - and now this habit works against me in a car like this which does not even need such a maneuver because I have a PDK 718 ) .

iphilips

Find a safe open space and practice. You'll figure out pretty quickly if you're hitting the gas pedal or not.

nicolae1

After the car is fixed I will put a small camera in the footwell than I will try few stops. I was just curios if somebody else had the same issue.

GregWormald

I've never had to 'real emergency stop' in this car but on several trials on a deserted road I found the stopping to be impressive. On one go it terrified my passenger.

Greg Fishman

The stock brakes in these cars are great and you should have no issue with braking power. Have a shop confirm the brake pads are the stock ones the car should have come with. It sounds like you may have lost hydraulic pressure which can happen if brakes are over heated or has old fluid.
Make sure there are no leaks, brake fluid reservoir cap is tight and brake fluid is at the right level too. I would bleed the brakes and make sure it has fresh fluid.
If you are hitting the gas then there isn't much I can say except don't do that!

nicolae1

The brake pads are stock ones because I bought the car from new. For the rest I'll have a check as you said. Thank you for your help.

BlueNorther

I hate to admit it but I've had the same experience 3 times with my 911, not braking like it should under sudden hard braking. Never had an issue like that with my prior Caymans, including 3 track days with the 981. Since Porsche brakes are normally excellent and confidence inspiring, I have also been wondering if I had managed to hit the accelerator pedal in those instances (though I hate to admit it). I have Renline accelerator pedal extenders, so it makes it easier to "heal toe" . I use my forefoot, not heal, so my foot is never far from the accelerator + extender when braking even normally. I had the same extender set on the 981 but never had an issue, so I'm not entirely sure, but I haven't experienced this again now that I'm paying more attention.

Sorry to hear you had an accident from this. Porsche brakes are so good you usually have to worry about being rear ended by someone not braking as quickly, not the other way around!

I agree with above trying a few hard braking attempts on the open road.

Mike Murphy

Any scenario where the brake pedal goes all the way to the floor indicated a problem with the brakes.

Consider that a stock Porsche braking system can absorb maybe 2x/3x horsepower worth of energy/heat.

Under maximum braking conditions, in just about any car I’ve ever driven, if you apply maximum brake pedal pressure, you should be either locking up the wheels (non-ABS, old cars), or invoking the ABS (which would should be able to feel). If that’s not happening, something is wrong, or you aren’t putting enough brake pedal pressure.

If non-stock brake pads are on your car, then cold, initial braking might be poor. If it’s been raining or humid or the car say for 1-2 weeks, the rotors might be rusted (normal). You should try to brake hard when nobody is around coming to a stop sign to get the rust to wear off and some heat in the pads.

Are you washing your wheels with anything? Some detergents and tire treatments make the rotors/pads slippery.

nicolae1

I pressed the brake quite hard because I saw that I am going to hit that car. I have stock brake pads , I did not washed my wheels with something weird , however I did not felt the ABS was working.
At least now I am aware that pressing the gas pedal could be the reason. It is first step in trying to avoid this in the future. If I would have known this before , maybe the end would have been better. At least I would have released the brake pedal and pressed it again but being careful to not tough the gas. The fact that somebody else experienced this problem proves something to me.

Mike Murphy

You probably don't want your foot sharing space between the brake and the gas. One foot on each pedal - try to practice that.

Still, Doesn’t add up. Even if you are hitting the gas, pressing the brake pedal as hard as you can would invoke front wheel lock up or ABS engagement - assuming your car is RWD only. And you would feel that or even hear it or see the ABS lights on the dash.

If the pedal goes to the floor, there is probably air in the brake line.

nicolae1

I will renew the brake fluid anyway. Than I will do some brake tests and see what is going on.To know for sure. Best regards.

jimmuller

You probably know this already but some people don't so I'll throw it out. ABS doesn't mean anti-skid. It means anti-lock. It detects when a wheel is skidding and repeatedly releases and re-applies braking very fast. The goal is to let you steer. Wheels which are skidding have no steering capacity. ABS doesn't decrease braking distance very much. Some people think ABS will dramatically improve braking and keep them from hitting something. By itself it doesn't.

Regardless, you should have those brakes checked.

CaymanMatt

My thoughts:
I have felt something similar to what's being described here on various cars including our Cayman. For me it has only happened when the car was cold and this was the first real use of the brakes after starting to drive. Certainly longer braking distance and it seems that pressing harder doesn't really help a lot. I suspect it is caused by something like surface rust that has formed on rotors after not having driven the car for a while, dirt on rotors pads, etc - essentially something has gotten between the pads & the rotors that needs to be scrubbed off. The explanation to myself is that the first use scrubs whatever the interfering material is off the rotors and pads and then the subsequent releasing of the brakes allows the stuff to escape, allowing the brakes to return to normal. The fact that the pads are cold of course makes it worse and unfortunately that first stop is then not normal distance. BTW, it could be just cold pads but to me that means this issue should happen every time the car is driven cold and this does not happen. Therefore it's something else.

Solution for me: use the brakes sooner than when they are really going to be needed.

If this was your first stop of the day, this could explain it. If not, then I suspect it's a different issue.

YMMV & MOO!

nicolae1

Every time I encountered this problem the car was quite cold. ( One time was after I left from wash car , so this time does not really count because the brake pads and rotors were wet so only the other two instances really matter ) . But it was not the first brake of the day. For example , last time , I started and drove for 5 km , than stopped there for 30 min , then drove again for another 5 km until I had the accident. there is no possible to drive for 5 km without pushing the brake now and then. So , there were little brakes but not a major one. One thing that is common both times is that it was in five km distance for the start , I had few small brakes and when I pushed for the major one it was fading. You said very well : pressing harder doesn't really help a lot. Other thing that is common is , both times , I was driving fast for most of the distance without braking hard , so I think that rotors had plenty of time to cool down and when I pressed the brake there was no efficiency. But I do not think there was any rust because it was only about 10 hours from the last time I drove the car. But maybe , just maybe , the last time I drove the car , I dove it fast and I stopped the car with the brakes very hot. Maybe because of this something happened. Like small part of the resins on the surface of the brake pad melted and there was some gas trapped there between the rotor and the pads. Hence the inneficiency. I will ask people more knowledgeable than me , to see if this theory might be true. Thank you for your contribution.

Greg Fishman

Another thing to ask your service center to check is the hub bolts. (not lug bolts but the big center bolt that holds everything together). If this is loose it would cause the rotor to wobble and maybe push the pads back. Then when you apply the brakes you get a long pedal. It can happen even if the hub bolt is tight but you would have to hit something pretty hard to cause this. When I used to race I would always do a "confidence tap" on the brake as I headed to a major brake zone to make sure the pads were seated correctly.