I have to ask what was the ambient temps when you guys tracked? The reason is that here in s. Fl the last two events, the air temps were in the high 90's and three of us experienced a weird brake loss. It feels as though ABS is releasing brake force even though there is no lockup. I was wondering if anyone has heard of the ABS unit overheating?

 

That has happened to me twice in my '05 Carrera S with steel discs;once at VIR and once at RIR (Richmond International). Ambient temps both times were in the high 80's.
I was braking from about 70 at VIR and 100 at RIR. The brakes, in each instance, returned to normal operation for the rest of the lap;although I wasn't pushing as hard.

I haven't encountered a simliar problem with the PCCB's on the GT3, yet.

Carl

 

Tracked twice in mid to high 90's with pretty high humidity as well. Never had the problem. Only thing was that a buddy's RS' Oil Temp rose to nearly 120 degrees. Mine hovered around 100 degrees.

 

Mitch-

I've had a similar experience in a track prepared 993 with mismatched tire sizes. The cure for it was to shorten the braking distance and increase the brake pressure (foot on pedal) and not use that tire combination again.

Hank

 

The Brake pedal is the hardest to master....

 

I have to ask, because the only time i've ever felt what you describe was braking hard while cresting a slight hill, could it be due to a small elevation change perhaps?

Matt

 

Some points:

-It has only happened to me twice.
-There is NO wheel lock-up. ABS does not pulse. There is no tire smoke.
-The pedal remains firm. No matter how hard I push, the braking force does not increase.
-The very next application is completely normal.
-It happens with stock wheel/tire combination.
-It happens deep into the session.

I am bringing my car to the race shop and we are going to give the ABS unit some air space to keep it cooler and see if that solves the issue.

 

it sounds EXACTLY like green fade. i think i mentioned that on another thread. if it happens, goes away, and the pedal always feels ok, it's the only thing i can think of.

from EBC's website:

BRAKE FADE EXPLAINED
All pads contain some organic (living) materials. Resins that bind pad compounds together are organic - petro-chemical products. As these overheat the resins revert to gas and cause the pads to “aquaplane” on a gas film which is called fade. Some pads only fade once or twice and then settle down (Green fade or bedding in fade). Other, cheaper pads suffer from continual dynamic fade, sometimes at surprisingly low temperatures.

 

I've been using Pagid RS-14's for the past 3-4 years without ever experiencing "green fade". I doubt this is the issue.

 

I would guess it is some kind of electronic/software glitch. Perhaps the electronic bias is confused and cannot proportion correctly? Do you have any kind of data logger that might pin point the conditons under which the occurences trigger?

 

You mentioned other guys with slotted rotors -- which manufacturer?

 

Performance Friction.

 

Pity. They're wildly expensive.

Which pads for those PF slotteds?

 

Mitch,

Aren't you running tires that are of a significantly different diameter than stock tires? If so, ABS believes that one or more wheels are slowing a different rate than the others and releases pressure the slower turning wheel(s) because it believes that those wheels are sliding.

I have experienced it several times.

Hank

 

That's a PSM thing, not ABS. ABS does four independent channels.