Traction control issue?

[Suberman]

ABS has its limits. One unfortunate side effect which can catch out even ordinary road drivers, though they will not be aware of the reason for the crazy behaviour of their vehicle, is the inability to lock the wheels in a yaw event means you really have to keep steering the vehicle through the entire emergency event. ABS means the car will continue to travel in the general direction the front wheels are pointing. On the track at very high speeds this can be very dangerous and may be a reason ABS is not found on competition cars.

ABS is tricky to duly implement on motorcycles also, for different reasons.

EBD has no such drawbacks unless ABS also operates. As I understand it, EBD uses wheel speed sensors and the ABS line pressure bleed valving to equalize wheel slip among the four wheels regardless of brake line pressure or wheel loading. This maximizes total braking force. In theory it could be programmed to permit four wheel lockup with the singular advantage that the lockup would be truly simultaneous.

I doubt very much that EBD would remain active if the ABS were to be disabled on a street car as it would be difficult to write the software. Also, if the ABS malfunctions on a road car the brake line pressure relief valves MUST remain closed so EBD could not operate. A competition car could just return to the pits if a partial failure of the ABS/EBD were to occur.

For this reason I doubt road cars rely only on electronics to limit line pressure to the rear brakes. The mechanical proportioning valves are anvil reliable, rarely failing in the entire service life of the vehicle. Indeed, if they do fail it is usually the load variable mechanism that fails, the rear line pressure still gets limited but defaults to the lowest, light load setting. The consequences to an ordinary driver of ABS/EBD failure with no backup mechanical brake proportioning valve could be very serious indeed.

I'm puzzled by the post suggesting rear droop could be reduced by fitting stiffer springs and deleting the roll bar when the opposite would be the case. Roll bar springing is ineffective for simultaneous wheel movements on the same axle.

[Porsche]

Originally Posted by Kodename47

Check out Fensport's car here in the UK. Its a turbo track car (GT86R) and he runs the Toyota Sprint Series. He removed the ABS fuse and did nothing but slow him down. The brakes just liked to lock up and made the car unstable.
http://www.gt86ownersclub.co.uk/foru...able+ABS#49563

Thanks for this.

Their experience is what I anticipated.

When ABS systems were first implemented on road cars by Audi and Mercedes, I think(?), they had switches for the driver to turn ABS OFF. I remember that the racing Corvettes had ABS OFF switches many years ago. An interesting Car & Driver(?) article had a journalist riding along with a Corvette factory driver at a race track, the driver spun and smacked into the Armco barrier. He said "Oops, I forgot I had ABS turned ON." The ABS took him right into the barrier.

With further advancements in technology I suspect that all of these systems are integrated into a design that no longer permits one to turn OFF the ABS safely; other required systems are dependent on the ABS functioning.

Bosch Motorsport offers a racing ABS system, albeit at $8000+. But, even their far more sophisticated system is apparently not without some problems. Porsche 911 drivers still experience "ice mode" under some conditions even with the expensive Bosch system.

I guess I'll just have to abandon any thought of turning ABS OFF.

[The_Societan]

I haven't tried this "pedal dance" you speak of, but it reminds me of something.

"For Infinite Traction, press and hold X, then press Triangle, Square, Square, Circle, Select, R1, L1, release X, Press and hold R2 then press Down, Up, Left, then release R2. Remove your left shoe and sock and (with your right hand covering your navel) press X with your big toe and Triangle with your pinky toe. If done correctly, you should hear a beep."