mjb

Just curious, and this may be a dumb question, but do 996 based race cars typically have PSM disabled? I'm assuming so but you mentioned a "steering angle code" was thrown. ABS based code or PSM?

I haven't heard of the ABS issues you're describing with any frequency on street GT3's that are tracked regulary, and running with race pads. Albiet they're typically not running slicks (but maybe Hoosiers), and during race conditions; but run hard and fast none the less. GT3 brake system seems pretty bullet proof with the right fluid.

Darren

There is a g-force sensor on the center tunnel of the car that is used by the ABS system along with the wheel speed sensors.

If you look at the PDF for the Bosch M4 Standalone kit, the part is in the first picture right by the case:
http://www.bosch-motorsport.com/cont...rochure_en.pdf

I'm sure the PSM system also uses the readings from this sensor but in my car the PSM is disabled.

997gt3north

I feel your pain, I don't race or speed test in my stock 997gt3 and I get these issues all the time - I have widely posted about the issue on the 997gt3 rennlist forum. You don't need to look any further than the Street GT3/RS that WR will be racing with slicks at the upcoming 24hour race - Porsche / Bosche knows there is a major problem and they are reprogramming / fixing the unit to work properly - it is totally beyond me why the street GT3 car is sold with an ABS controller that is potentially fatal (ask me how I know).

I will bet major money that if there is a next gt3/rs they will address this issue as I predict with near certainty that one way or another this fatal flaw will come to light - someone with enough money will get very seriously injured when the brakes don't stop the car but float them straight into a wall.

If I were you, but I am not, I would not "race" your car with the OE ABS system - it will eventually with enough attempts end very badly for you.

https://rennlist.com/forums/997-gt2-...on-slicks.html

jakermc

I'm not experiencing the issues described in anywhere near the frequency mentioned and I'm also running Hoosier slicks (250/285) with Pagid Blacks, GT3 rotors and calipers, etc.

Rough pavement or transitions have caused the issue to surface but I have also found that adjustments to the shock settings can help mitigate this. Other than rough sections, I never even get into the ABS.

When it has occurred it has occurred consistently in the same spots and reacts to my inputs in a consistent manner. I can just back off a little bit, as you would with a non-ABS car that is locking up, and all is good again. It perhaps negatively impacts lap times a bit but I would not call it a dangerous problem.

onefastviking

I bet it's more than 5lbs per corner.

We've done the Grand Am set up as far as rotors and calipers go. Played with different pads and fluids. Have been thru multiple brake cooling upgrades. Everytime I get the brakes working well enough I then go make the car a little faster and then we are running out of brakes again. It's a crazy cycle ! I'm afraid that we might have to do the extra weight and do the cup brakes one of these days soon.

The main problem with this system isn't tire size related, it's the ABS. The GT3 system won't help it, it's very mildly better. Rob, you have the problem, it just hasn't reared it's ugly head yet. You will know when it does, it will be a real oh **** moment and then come talk to me.

There are some downsides to the alternate ABS systems available.

onefastviking

Do you remember Jay's white car, the one that got totaled ?
I'd say it has potential to be dangerous. That being said, the standard ABS system is fine on the car for what the cars were designed for, but when you throw on sticky tires, suspension, etc and really start to push things then you reach it's limits.

Paul 996

I wonder if this is a symptom only for the newer cars.

I have to ask if anyone has experienced anything remotely like this on the pre 2002 cars? I have never in my 1999 and pushed it pretty hard around the track on big Hoosiers. at one point 275 front, 315 rear

jrgordonsenior

Yea it's actually more like 10lbs. but I didn't want to scare off anyone considering making the switch. I prefer to just keep lightening the car.

Hey there may be something to what Paul says about the 99-01's not having the same issue or at least not as severe. I was braking the bleep out of the car at Cal Speedway weekend before last coming out of the banking on cup Yokohama slicks. Overcooked it once but that was driver error....

mglobe

Another data point: My 996 Spec is a my2000, and weighs 3020 with me in it. Stripped, caged, and with the spec suspension (soon to be upgraded to the new JRZ package) Running stock brakes with SRF, and PF97 pads. The car does not have PSM. I'm racing it, and pushing it reasonably hard. Running on 245/285 BFG R1's. No problems at all with ABS.

onefastviking

I've seen it on a 2000 996, Boxster's, and a good friend(great wheel) has discussed it occuring with his 89 951. It doesn't happen until you push the car very hard. All with sticky tires and driving very fast.

onefastviking

It is also track dependent. As Rob pointed out, bumps especially just before a corner = no good.
TWS you will never feel it. Bumpy street course, MSRH or MSRC, maybe even ECR you will swear you hit ice.

J richard

This is interesting... And I am completely out of my element here but the earlier 964/993 cars had an issue with the non cup abs basically getting confused mainly during a spin or over really rough gaitors and releasing all brake function until the system was reset... The solution was a abs overide switch. This still gave you all the braking capability of the system just no abs function, I run the override all the time on mine, I wonder if this is just a further example of the same inherent bosch design...

onefastviking

Bosch improved it over the years but it's effectivily the same problem. It's an ABS system for street cars and street conditions, not slicks and over 1G conditions.

trackjunky

FWIW, I have a '99 and have had the *oh ****'s* twice at TWS. Coming into T3 going clockwise and braking for 10 going counter clockwise. In both cases the pedal went to the floor and I had to let the system recycle before the brakes worked.

It also happened in Globes car. Mike if you remember when we went around the banking in turn 15 going clockwise. The pedal went to the floor. We thought that maybe the brakes needed to be bled.

Funny thing with my car is that I can't get it to repeat the problem as I have come into those same turns faster on other occasions. But in every occasion the pedal went to the floor, I had zero brakes and I had to come completely off the brakes to get them to work again. Scary. (DOT race tires in all situations)

mglobe

I'd forgotten about that Bill. I had problems for a while with getting air out of the clutch hydraulics. I suspect that that was the source of that particular problem rather than the ABS. Same thing happened to me once at T3 with Dave in the car. Went straight off into the cones.