sims

I have been experiencing early interferences by the ABS system during the race sessions. It forces me to break much earlier than the GT3s. Trying to understand the issue, I was told that the tyre pressure system "RDK" is influencing the ABS, depending the tyre pressure. Anyone faces the same issue? How was the problem resolved? It is interesting to note that the rear brake pads are experiencing stronger usage.

Would appreciate any hint.

dan360

You might want to consider technique since you don' t mention it at all.

Is it a bumpy track? Are you using super hard initial brake pressure?

If you are using very hard initial brake pressure you may be getting into the ABS straight away, it will then take a while of less pressure to stop, especially on a bumpy track and if you keep the pedal mashed. With ABS its better to brake a tiny bit progressively, ie a very quick increase in pressure to have the car take a set then threshold max brake pressure. Note I'm not talking about progressive braking where you gradually change pressure like one would on the road, I'm talking about the difference between mashing the pedal instantly and pressing it down to full threshold in one smooth, but somewhat progressive movement. Its a matter of a tenth of a second.

Bob Rouleau

Are the holes in the rotors plugged with pad material? The GT2 also has another quirk, the ABS sensor is located in such a way that it collects rubber from the track. When the sensor gets crudded up, the ABS comes on way too soon. This is fairly common on the GT2 and I bet it is what you have. Find and clean off the sensor and or the toothed wheel which generates the rotation signal for the sensor. You need to remove the wheels to do this.

best,

C.J. Ichiban

wow, great info Bob!

to the OP- ABS kicks in on the ceramics very early when they're cold, or the tires aren't up to operating temperature...one of the quirks of the PCCB ABS...

you have to drive it with TC OFF otherwise the rear pads will get cooked. the TC uses automatic braking if you're spinning the wheels too much coming out of corners...

also- for track purposes you should use the green PCCB motorsport pads. let me know if you need the part number. there was a service bulletin for GT2 cars that see a lot of track time to switch to these.

todinlaw

OK give me an education hear, the TC only kicks in when you are on the accelerator and you get wheel spin and if you have the sport button on the thresholds are higher, I have heard people talk about TC accounting for more rear pad use but I have burned my rear pads about 2 to 1 with the fronts but never have felt TC kick in( or see a light) car is vary smooth and predictable when I rotate the car in the corners??

C.J. Ichiban

first of all frank- if you're looking at the dash lights, we've got bigger problems!

okay about TC in the GT3...do you use TCS? if you do, that is your pad wear. the software and hardware is designed to make you feel like a hero, and with the controls on, you will look like one as the rear of the car magically slots into place after getting too frisky under accel- you probably won't feel anything. It's not like the mercedes benz cars that will light up when it kicks in while you're on the track or drifting. In the 997GT3- when you're on the track, you should never use TCS, and always use Sport Button ON.

it's true that the sport button engages a different mode in the TC settings- and maybe it allows for 10* of slip angle instead of 6.5* before it starts working, but either way, almost any good driver should operate in and around that range for maximum tire performance anyway.

about TC in general- there are 3 things (maybe more, but this is seat of pants time) that TC can do to control a car that has been deemed by the onboard gyroscopes to be "out of sorts"

-cut fuel to engine (less power to wheels, less slipping)
-cut spark to engine (less power to wheels, less slipping)
-use ABS type fluttering to reel in the individual wheels/tires/tyres that are slipping away.


F1 cars with traction control of yesteryear used electronic engine related TC systems, but almost all the street cars simply use the brakes.

in my experience-after about 4500track miles, I'm on my*3rd set of pads- one stock, 2 greens and always with the TC button off. Pad wear is very even and the greens I just pulled off probably still have a lot of life in them. I've spun a few times that most likely would've been reigned in by TCS, but then I wouldn't really learn any lessons, would I?

Yargk

The technical expertise on this site never ceases to amaze me, hat's off to Bob and CJ

Bob Rouleau

One adder to CJ's post. With the torque of the GT2 it is too easy to invoke traction control especially exiting slow corners in second or even third gear. Unless you see the light flash, it isn't easy to tell it is working its magic. TC usualy feels like you hit a small bump, only there is no bump.

Locally one guy wore out his rear ceramic rotors after less than 3000 miles! His brutal throttle application, TC and a local track with a ton of 2nd gear corners was the reason. It was an expensive driving lesson since PCCB rotors are stupidly expensive.

BE CAREFUL - if you are using TC (and you are for sure) you need to learn to progressively accelerate otherwise you will lose the back end of the car. I always run TC off and my rear pads last a bit longer than my fronts. Accelerated wear of the rear pads is almost always due to harsh acceleration and the intervention of traction control. So CJ is right. A good driver will always turn it off. On the other hand if you have gotten used to mashing the throttle on corner exit, TC has been saving you. Be careful, please.

Bob Rouleau

Thanks Yargk - the help one can get on this site is what makes Rennlist so special.

cgomez

Agree with all that has been said above.

Never had any ABS issues and my rear pads last 2X the fronts as I drive ALL the time with TC + SC off, even on the street.

Remember that the GT2 (different to GT3 and RS) has also SC (Stability control) and this system also uses the rear brakes a lot to control understeer/oversteer. Therefore brake wear would be even higher than in a GT3 if you drive hard with the nanny systems ON.

OldGuy

You need to turn it over to our tame racing driver. Some say his eyelids are titanium and his knee are hydraulic, all we know is they call him The STIG.

The Stig ALWAYS turns TC OFF!

was there not a similar problem (early ABS) on the 996 GT2?

John Boggiano

While we're on brakes - I was looking at a picture of a GT3 in profile last night when an obvious factor in rear brake pad wear hit me - as the rear calipers are only 4-piston, and especially as we know the GT3 has an unusual degree of rear bias to the braking, even without TC operating surely the rear pads are doing about 50% extra work than the fronts so they are bound to have a much harder time.

And speaking of which, is the rear bias to the 3's brakes truly a rear bias, or is it just less front bias than would generally be found? I hope that makes sense.

NJ-GT

The brake bias on the 997 GT3 is perfect. I could not get the 996 GT3 to do this unless I went with a proportioning valve or bias controller.

Yes, there is more wear on the rear brakes, but that's where most of the car weight is located, so it's good to take advantage of that.

sims

thank you for all the hints - i am amazed by all the great insights

Some background info:
- drive the Sprint and Endurance races as part of Porsche Sports Cup
- drive with TC and SC off at all times
- got the green pads
- used 2 sets of rear pads and 1 set of front pads on one race weekend in Magny Cours (a course that has many high-speed straights with low speed corners)

The symptoms of my GT2, do indicate that I am driving with TC on.
I ll definitely check the sensors - that would be an easy fix.
Nobody referred to RDK "Tyre Pressure Control". Is this only a myth?

C.J. Ichiban

sims- you might have some electronic gremlins in your abs system if you're running with TC off and SC off and still have all these issues. also, what is your brake fluid situation? if your fluid has gotten boiled at some point, you might have damaged the rear pistons in the caliper.

also, by Tyre Pressure, are you referring to the reported info from the computer? they are MEGA inaccurate.