PCCB braking issue at Sebring
07-28-2007, 12:52 AM
#31
I normally just keep my foot in when the ABS start to cycle with my 993. With the RS, I now back off and then stomp on them again, but by then I usually would have missed my turn in so would be doing lots of strange things to get the car pointed in the right direction. It is possible that the car needs wider front tires to take advantage of the big brakes. However, the tail wagging means something weird is going on with the program. Will try to dial in more negative camber, bit more toe out in the front and toe in at the rear, see if that change the behaviour.
07-28-2007, 05:07 AM
#32
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Originally Posted by scss98
I normally just keep my foot in when the ABS start to cycle with my 993. With the RS, I now back off and then stomp on them again, but by then I usually would have missed my turn in so would be doing lots of strange things to get the car pointed in the right direction. It is possible that the car needs wider front tires to take advantage of the big brakes. However, the tail wagging means something weird is going on with the program. Will try to dial in more negative camber, bit more toe out in the front and toe in at the rear, see if that change the behaviour.
The ABS cycles each wheel individually, but you feel the pulses whether one or all four wheels are beyond their adhesion limits. I've worked with world rally masters and with track stars and the best development drivers, they ALL increase the effort on the brake pedal when the ABS does go off.
As far as the motorsport ABS, slicks and the 996GT3 Cup are concerned, it is preferable to try and keep your braking just on the edge of ABS intervening, it is slightly less efficient if it intervenes for a professional driver (ask WH), but usually still effective for a club racer.
The latest generation ABS will help you steer under braking, practice this.
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07-28-2007, 01:39 PM
#33
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Originally Posted by Terry L
This is all so disconcerting since I have just come through the same problem in my Lotus Elise - at the end of a long fast straight, pedal is high, hard as a brick, and maybe 25% brake force - brake usually returns just in the nick of time. It was speculated that the ABS sytem didn't like the aggressive pads coupled with a bumpy brake zone. I will say that at the Glen two weeks ago I had no brake problems with the GT3 running RS19s, suspension on firm, and the car saw 150+ lap after lap, so I assumed I had left the problem with the Elise.
07-28-2007, 10:48 PM
#34
Actually, I was the guy who announced that the fix had been found and it was a leaky check valve at the brake booster. The head Lotus tech in the US had suggested this was the problem, based on my description and I thought it had beeen solved after I replaced the valve. However, although VIR was perfect, the problem resurfaced at Summit Point although not as severe and more clearly feeling like ABS rather than just no brake boost at all. I think there were two separate things going on at the same time which made it so difficult for us to discuss the problem (or problems) intelligently.
07-31-2007, 12:30 AM
#35
Well I hope other guys with RS will try their cars on the track and see what they think of their brakes. I talked to a few GT3 guys and they don't have the same issue. The only thing I've heard them say is that the car does not like trail braking. Who knows whether this is an RS issue or just some little part in the system being out of spec!
07-31-2007, 10:43 AM
#36
Originally Posted by Nordschleife
What do you do when you feel the ABS start to cycle
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Originally Posted by Nordschleife
The ABS starts to intervene when one of the four wheels has reached its limit of adhesion, that means there are still three wheels with unused retardive potential. under these circumstances, redouble the force on the brake pedal.
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